2Al(s) + Fe₂O3(s) → Al₂O3(s) + 2Fe(s)
ΔΗ = −847 kJ
Railroad maintenance initiates a
thermite reaction of 4.0 mol Al to connect
two lengths of rail using the reaction
above. How much heat is released
during the reaction?
9rxn = [ ? ] kJ

Answers

Answer 1

The heat released during the reaction is -212 kJ. Heat is a fundamental concept in physics, chemistry, and engineering and plays a critical role in many natural phenomena, such as thermodynamics, phase transitions, and thermal radiation.

What is Heat?

Heat is a form of energy that can be transferred from one object to another as a result of a difference in temperature. Heat flows from hotter objects to colder objects until they reach thermal equilibrium, meaning that their temperatures become equal. The amount of heat transferred is typically measured in joules (J) or calories (cal) and is related to the mass of the object, the specific heat capacity of the material, and the temperature change experienced.

The ΔH for the reaction is -847 kJ.

The stoichiometric coefficient of Al in the balanced equation is 2. This means that 2 moles of Al are required to produce 2 moles of Fe and 1 mole of [tex]Al_{2} O^{3}[/tex].

Since the reaction uses 4.0 mol of Al, it will produce 2.0 mol of Fe and 1.0 mol of [tex]Al_{2} O^{3}[/tex].

The amount of heat released during the reaction can be calculated using the equation:

ΔH = q/n

where ΔH is the enthalpy change, q is the heat released, and n is the number of moles of the limiting reactant (in this case, Al).

Substituting the values gives:

ΔH = (-847 kJ) / 4.0 mol = -212 kJ/mol

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Related Questions

A gas occupies 12 L of a container at 2.75 atm. What is the volume of the gas if the pressure becomes 7.25atm?

Answers

Boyle's Law-

[tex]\:\:\:\:\:\:\:\:\:\:\:\star\:\sf \underline{ P_1 \: V_1=P_2 \: V_2}\\[/tex]

(Pressure is inversely proportional to the volume)

Where-

[tex]\sf V_1[/tex] = Initial volume[tex]\sf V_2[/tex] = Final volume[tex]\sf P_1[/tex] = Initial pressure[tex]\sf P_2[/tex] = Final pressure

As per question, we are given that -

[tex]\sf V_1[/tex] = 12 mL[tex]\sf P_1[/tex] = 2.75 atm[tex]\sf P_2[/tex] = 7.25 atm

Now that we have all the required values and we are asked to find out the final volume, so we can put the values and solve for the final volume -

[tex]\:\:\:\:\:\:\:\:\:\:\:\:\:\:\:\star\:\sf \underline{ P_1 \: V_1=P_2 \: V_2}[/tex]

[tex]\:\:\:\: \:\:\:\:\:\:\longrightarrow \sf 2.75 \times 12= 7.25 \times V_2\\[/tex]

[tex] \:\:\:\:\:\:\:\:\:\:\longrightarrow \sf V_2 = \dfrac{2.75 \times 12 }{7.25}\\[/tex]

[tex] \:\:\:\:\:\:\:\:\:\:\longrightarrow \sf V_2 = \cancel{\dfrac{ 33}{7.25}}\\[/tex]

[tex]\:\:\:\: \:\:\:\:\:\:\longrightarrow \sf V_2 = 4.5517........\\[/tex]

[tex] \:\:\:\:\:\:\:\:\:\:\longrightarrow \sf \underline{V_2 = 4.56 \:mL }\\[/tex]

Therefore, the volume will become 4.56 mL if the pressure becomes 7.25atm.

Which term is used to describe why we can smell air freshener across the room shortly after it has been sprayed? A. elastic collisions B. osmosis C. diffusion D. temperature​

Answers

The diffusion term is used to describe why we can smell air freshener across the room shortly after it has been sprayed, hence option C is correct.

When you spray the air freshener, the matter goes from a high concentration region to a low concentration area that is far away from the spraying location. Diffusion is the term used to describe this material movement.

Diffusion is the overall net movement of something from a higher concentration to a lower concentration.

The term "diffusion" is used to explain why we can smell air freshener across the room quickly after it has been applied.

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why does f2 have such high standard reduction potential, and why are the standard reduction potentials for alkali metals negative?

Answers

The standard reduction potential is a measure of the tendency of a species to gain electrons and undergo reduction. A higher reduction potential means that a species is more likely to undergo reduction.

The high standard reduction potential of F2 can be attributed to its small atomic size and high electronegativity. Fluorine has a strong attraction for electrons due to its high electronegativity, and its small atomic size allows it to tightly hold onto its valence electrons. As a result, F2 has a strong oxidizing power and a high tendency to accept electrons, leading to a high standard reduction potential.

On the other hand, the standard reduction potentials for alkali metals are negative due to their low electronegativity and large atomic size. Alkali metals have a strong tendency to lose their valence electrons due to their low electronegativity and relatively large atomic size, which makes their valence electrons more loosely bound. As a result, they have a low tendency to accept electrons, and their standard reduction potentials are negative.

It is also important to note that standard reduction potentials are measured under standard conditions, which may not reflect the behavior of the species in other environments. Factors such as the presence of other species, the pH, and the temperature can affect the behavior of species and their standard reduction potentials.

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the dissolution of ammonium nitrate occurs spontaneously in water. as nh4no3 dissolves, the temperature of the water decreases. what are the signs of the changes of h, s, and g for this process? a. incrementh < 0, increments > 0, incrementg < 0 b. incrementh > 0, increments < 0, incrementg > 0 c. incrementh > 0, increments > 0, incrementg < 0 d. incrementh < 0, increments > 0, incrementg < 0 e. incrementh < 0, increments < 0, incrementg < 0

Answers

The correct option is d. increment H < 0, incrementS > 0, incrementG < 0.

When NH4NO3 dissolves, the temperature of the water decreases. What are the signs of the changes of H, S, and G for this process?The sign of changes in enthalpy (ΔH) for the dissolution of ammonium nitrate (NH4NO3) in water is negative.

It means that the process releases heat, and it is exothermic. The dissolution of NH4NO3 in water is a spontaneous process and hence its entropy change (ΔS) is positive.

Therefore, the dissolution of NH4NO3 in water leads to an increase in the entropy of the system. Since the dissolution process is exothermic, the change in Gibbs free energy (ΔG) is negative, indicating that it is spontaneous.

Thus, the signs of changes in H, S, and G for the dissolution of ammonium nitrate in water are: ΔH < 0 When NHd ΔG < 0.

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what is the selenide ion concentration for a .200m h2s solution that has the stepwise dissociation constant

Answers

To determine the selenide ion (Se2-) concentration for a 0.200 M H2S solution that has the stepwise dissociation constant, we need to use the equilibrium constants for the reaction of H2S with water and for the reaction of HSe- with water.

The stepwise dissociation of H2S in water can be represented as:

H2S + H2O ⇌ HS- + H3O+

K1 = [HS-][H3O+] / [H2S]

The stepwise dissociation of HSe- in water can be represented as:

HSe- + H2O ⇌ Se2- + H3O+

K2 = [Se2-][H3O+] / [HSe-]

We are given that the concentration of H2S is 0.200 M. At equilibrium, some of the H2S reacts with water to form HS- and H3O+. We can assume that the initial concentration of H2S is much greater than the concentrations of HS- and H3O+ formed, so we can approximate the concentration of H2S to be 0.200 M at equilibrium. We don't know the concentration of H3O+ at this point, so we will express it in terms of x.

H2S + H2O ⇌ HS- + H3O+

Initial concentration: 0.200M 0 0 0

Change: -x +x +x

Equilibrium concentration: 0.200-x x x -

Now we can use the equilibrium concentrations to calculate the values of K1 and K2 using the given stepwise dissociation constants:

K1 = 1.1 × 10^-7 = [HS-][H3O+] / [H2S]

K2 = 1.3 × 10^-13 = [Se2-][H3O+] / [HSe-]

We can express [HSe-] in terms of [HS-] and [H2S] using the acid dissociation constant expression for H2S:

K1 = [HS-][H3O+] / [H2S]

1.1 × 10^-7 = x^2 / (0.200 - x)

Solving for x, we get:

x = 5.5 × 10^-5 M

This is the concentration of [HS-] and [H3O+] at equilibrium. To find the concentration of [Se2-], we can use the equilibrium constant expression for the reaction of HSe- with water:

K2 = [Se2-][H3O+] / [HSe-]

1.3 × 10^-13 = [Se2-](5.5 × 10^-5) / (0.200 - 5.5 × 10^-5)

Solving for [Se2-], we get:

[Se2-] = 2.6 × 10^-14 M

Therefore, the selenide ion concentration for a 0.200 M H2S solution that has the stepwise dissociation constant is 2.6 × 10^-14 M.

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if covalent bonding occurs because an atom wants to achieve an octet and therefore fill empty spaces in its orbital, how many covalent bonds would you think are formed by each of the atoms in

Answers

The number of covalent bonds generated by each atom in C, H, O, Cl, N, S, and P is as follows:

Carbon (C) has 4 valence electrons and needs to form 4 covalent bonds to achieve an octet.Hydrogen (H) has 1 valence electron and needs to form 1 covalent bond to achieve a duet.Oxygen (O) has 6 valence electrons and needs to form 2 covalent bonds to achieve an octet.Chlorine (Cl) has 7 valence electrons and needs to form 1 covalent bond to achieve an octet.Nitrogen (N) has 5 valence electrons and needs to form 3 covalent bonds to achieve an octet.Sulfur (S) has 6 valence electrons and needs to form 2 covalent bonds to achieve an octet.Phosphorus (P) has 5 valence electrons and needs to form 3 covalent bonds to achieve an octet.

Covalent bonding occurs when atoms share electrons to achieve a more stable electron configuration. In general, elements that are close to each other on the periodic table tend to form covalent bonds, while elements that are far apart tend to form ionic bonds. Atoms can share one, two, or three pairs of electrons to form single, double, or triple covalent bonds, respectively. The number of electrons shared is determined by the number of electrons needed to achieve a stable configuration.

The number of covalent bonds formed by each of the atoms in C, H, O, Cl, N, S, and P depends on the number of valence electrons each atom has and the number of electrons needed to achieve a stable octet. These numbers are based on the octet rule, which states that atoms will bond in such a way as to achieve a stable electron configuration with a full valence shell of 8 electrons (or 2 electrons for hydrogen). Covalent bonding occurs when atoms share electrons to achieve this stable configuration.

The complete question is

If covalent bonding occurs because an atom wants to achieve an octet and therefore fill empty spaces in its orbital, how many covalent bonds would you think are formed by each of the atoms in C, H, O, Cl, N, S, and P?

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an aqueous solution of ca(oh)2 with a ph of 14.235 is prepared in a 500.00 ml volumetric flask by adding 91.138 ml of a ca(oh)2 stock solution. what is the concentration of the ca(oh)2 stock solution (units are m)?

Answers

The concentration of the Ca(OH)₂ stock solution is 0.00511 M.

The pH of an aqueous solution of Ca(OH)₂ can be calculated using the following equation,

pH = 14 - log([Ca(OH)₂])

where [Ca(OH)₂] is the concentration of Ca(OH)₂ in moles per liter (M).

Since the solution has a pH of 14.235, we can plug this value into the equation and solve for [Ca(OH)₂]:

14.235 = 14 - log([Ca(OH)₂])

log([Ca(OH)₂]) = 14 - 14.235 = -0.235

[Ca(OH)₂] = 10^(-0.235) = 0.00513 M

The Ca(OH)₂ stock solution was diluted to a final volume of 500.00 ml by adding 91.138 ml of the stock solution to a volumetric flask and filling up to the mark with water. Therefore, the number of moles of Ca(OH)₂ in the stock solution can be calculated as:

moles of Ca(OH)₂ = concentration × volume = [Ca(OH)₂] × (91.138/1000) = 0.000467 moles

The stock solution was diluted to a final volume of 500.00 ml, so the final concentration of the Ca(OH)₂ solution is:

final concentration = moles / volume = 0.000467 moles / 0.500 L = 0.000934 M

Therefore, the concentration of the Ca(OH)₂ stock solution is:

concentration = final concentration × (final volume / initial volume) = 0.000934 M × (500.00 ml / 91.138 ml) = 0.00511 M

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2. a substance in the gas state has a density about times less than when it is in the liquid state. the diameter of a molecule is . what is the best estimate of the average distance between molecules in the gas state? a. b. c. d. 1000 d d 10d 100d 1000d

Answers

The best estimate for the average distance between gas molecules is therefore b. d, or 1 diameter.

The density of a substance in the gas state is typically much less than its density in the liquid state because the molecules are much farther apart from each other in the gas phase. The average distance between gas molecules can be estimated using the formula:

d =[tex](V / N)^(1/3)[/tex]

where d is the average distance between molecules, V is the volume of the gas, and N is the number of gas molecules.

Since the density of the gas state is about "times less" than that of the liquid state, we can say that the density of the gas state is 1/ times that of the liquid state. This means that the volume of the gas must be times greater than the volume of the liquid, assuming the same number of molecules.

Let's call the diameter of a molecule "diameter" and assume that the substance in question is a monatomic gas (consisting of individual atoms). The volume of one molecule of a monatomic gas is approximately (4/3)π[tex](diameter/2)^3[/tex]. Therefore, the volume of N molecules is N times this volume, or N(4/3)π [tex](diameter/2)^3[/tex].

Since the volume of the gas is times greater than the volume of the liquid, we can say:

N(4/3)π [tex](diameter/2)^3[/tex] = times the volume of the liquid

Solving for N, we get:

N = ( times the volume of the liquid) / (4/3)π[tex](diameter/2)^3[/tex]

Substituting this expression for N into the formula for d, we get:

d = [times the volume of the liquid / (4/3)π [tex](diameter/2)^3]^(1/3)[/tex]

Simplifying this expression, we get:

d = [(3/4) times the volume of the liquid / π [tex](diameter/2)^3]^(1/3)[/tex]

We can see that d is proportional to the cube root of the volume of the liquid and inversely proportional to the cube root of the cube of the diameter of the molecule. Therefore, we can say that:

d ~ V^(1/3) / diameter

Plugging in the values from the answer choices, we find:

a. 1000d: d ~ [tex]V^(1/3)[/tex] / diameter = [tex](1000)^(1/3)[/tex]/ diameter = 10.0 / diameter

b. d: d ~ [tex]V^(1/3)[/tex] / diameter =[tex]1^(1/3)[/tex] / diameter = 1 / diameter

c. 10d: d ~[tex]V^(1/3)[/tex] / diameter = [tex](10)^(1/3)[/tex] / diameter = 2.15 / diameter

d. 100d: d ~ [tex]V^(1/3)[/tex] / diameter = [tex](100)^(1/3)[/tex] / diameter = 4.64 / diameter

e. 1000d: d ~ [tex]V^(1/3)[/tex]/ diameter = [tex](1000)^(1/3)[/tex] / diameter = 10.0 / diameter

The best estimate for the average distance between gas molecules is therefore b. d, or 1 diameter.

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Can someone fill out the first table for me or tell me what needs to be written in the table

Answers

Answer:

In Table 6.1, the initial solutions of each metal are provided: Cu(NO3)2, Fe(NO3)3, and Zn(NO3)2. The table is asking for the results of the oxidation-reduction reactions that occur when these metals are reacted with each other.

In Table 6.2, the metals (Cu, Fe, Zn) are listed, and the table is asking whether each metal was oxidized or not, and what oxidizing agent(s) were involved in the reaction.

1. Zn is the most reactive metal because it readily undergoes oxidation when in contact with other metals. This is known as the activity series of metals.

2. The order of increasing reactivity is Cu, Fe, Zn.

3. The chemical equations for each single replacement reaction are:

Cu + Zn(NO3)2 → Cu(NO3)2 + Zn

Fe + Cu(NO3)2 → Fe(NO3)2 + Cu

Zn + Fe(NO3)3 → Zn(NO3)2 + Fe

4. Fe was reduced, and Cu and Zn acted as reducing agents.

Explanation:

Which description best reflects the strategy "adopt an identity"?

People who enjoy traveling frequent a restaurant that offers an "around the world" tasting menu.
People who love the Star Wars™ films flock to the opening of the new Star Wars™ theme park.
People who love the television series Game of Thrones™ book a tour of its shooting locations.
People who wear Nike™ sneakers "just do it" when it comes to challenging physical activity.

Answers

The description that best reflects the strategy "adopt an identity" is: People who wear Nike™ sneakers "just do it" when it comes to challenging physical activity.

"Adopt an identity" is a marketing strategy that appeals to people's sense of self-identity and the desire to express themselves through the brands and products they consume. The Nike™ slogan "just do it" encourages people to identify themselves as athletes or fitness enthusiasts and to associate that identity with the brand. By adopting the identity of a Nike™ wearer, people are not only buying a product but also adopting a lifestyle and a set of values that the brand represents. This strategy is effective because it creates an emotional connection between the consumer and the brand, which can lead to brand loyalty and repeat purchases.

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The Pacific Plate moves to the northwest at an average rate of 10 cm per year. Hawaii is in the middle of the Pacific Plate, 6,600 kilometers southeast of Japan, which is on the edge of several adjacent plates. If the Pacific Plate continues to move at the same rate and in the same direction, when will Hawaii collide with Japan? Show your work.

Answers

To solve this problem, we first need to convert the distance between Hawaii and Japan from kilometers to centimeters, which is the unit used for the plate movement rate.

6600 kilometers is equal to 6,600,000 centimeters (1 kilometer = 100,000 centimeters).

Next, we can use the formula:

distance = rate × time

to calculate the time it will take for Hawaii to collide with Japan.

Let t be the time in years. The distance traveled by the Pacific Plate in t years is:

distance = rate × time = 10 cm/year × t

So, the distance Hawaii moves in t years is 10 cm/year × t.

At the same time, Japan moves in the opposite direction at the rate of the adjacent plate, but we don't know this value. We can assume that Japan is stationary relative to the adjacent plate, so the distance it moves is zero.

The total distance between Hawaii and Japan is decreasing at a rate of 10 cm/year:

rate of decrease = 10 cm/year

So we can set up the following equation:

6,600,000 cm - 10 cm/year × t = 0

Solving for t, we get:

t = 6,600,000 cm / (10 cm/year) = 660,000 years

Therefore, it will take 660,000 years for Hawaii to collide with Japan, assuming that the Pacific Plate continues to move at the same rate and in the same direction.

why will the conjugate base of a weak acid affect ph? select the correct answer below: it will react with hydroxide it will react with water it will react with hydronium none of the above

Answers

The conjugate base of a weak acid affect ph because it will react with water. Option b is correct.

When a weak acid, HA, donates a proton to water, it forms its conjugate base, A-. This reaction is an equilibrium process, and at equilibrium, a certain percentage of the weak acid will have dissociated into its conjugate base and hydronium ions.

The conjugate base A- can then react with water to regenerate the weak acid and hydroxide ions. This reaction shifts the equilibrium to the left, decreasing the concentration of hydronium ions and increasing the concentration of hydroxide ions, which increases the pH of the solution.

Therefore, the presence of the conjugate base of a weak acid affects the pH of a solution by shifting the equilibrium between the weak acid and its conjugate base towards the acid side, decreasing the concentration of hydronium ions and increasing the concentration of hydroxide ions. Hence option b is correct.

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a current of 0.550 a passed for 29.0 min through a cuso4 solution. calculate the amount of copper deposited.

Answers

The amount of copper deposited in the CuSO₄ solution is 0.315 grams.

To calculate the amount of copper deposited in this case, we can use Faraday's laws of electrolysis. First, we need to convert the time given from minutes to seconds, and find the total charge passed.

Time (t) = 29.0 minutes × 60 seconds/minute = 1740 seconds

Current (I) = 0.550 A

Total charge (Q) = Current × Time = 0.550 A × 1740 s = 957 A·s

Now, we need to find the moles of electrons transferred using Faraday's constant (F = 96,485 C/mol).

Moles of electrons (n) = Total charge / Faraday's constant = 957 A·s / 96,485 C/mol = 0.00992 mol

The reaction for copper deposition is: Cu²⁺ + 2e⁻ → Cu

From the reaction, we can see that 2 moles of electrons deposit 1 mole of copper. So, we need to determine the moles of copper deposited.

Moles of Cu = Moles of electrons / 2 = 0.00992 mol / 2 = 0.00496 mol

Finally, we calculate the mass of copper deposited using its molar mass (M = 63.55 g/mol).

Mass of Cu = Moles of Cu × Molar mass = 0.00496 mol × 63.55 g/mol = 0.315

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The diagram shows the potential energy changes for a reaction pathway.
Potential Energy
B
Reaction Pathway
Part 1: Describe how you can determine the total change in enthalpy and activation energy from the diagram, and if each is positive or negative.
Part 2: Describe how the curve will look if the reaction was exothermic. Be sure to mention changes in the potential energies of the reactants and products and the sign
changes of the enthalpy.

Answers

Answer:

Part 1:

To determine the total change in enthalpy (ΔH) from the diagram, we need to look at the difference between the potential energy of the products and the potential energy of the reactants. In this diagram, the potential energy of the products (point B) is higher than the potential energy of the reactants (point A), so ΔH is positive.

To determine the activation energy (Ea), we need to look at the difference between the potential energy of the reactants and the highest point on the curve, also known as the transition state (point C). In this diagram, the potential energy of the reactants (point A) is lower than the potential energy of the transition state (point C), so Ea is positive.

Part 2:

If the reaction was exothermic, the potential energy of the products would be lower than the potential energy of the reactants. This means that the curve would be inverted, with the potential energy decreasing as the reaction proceeds. The potential energy of the reactants would be higher than the potential energy of the products.

The enthalpy change (ΔH) for an exothermic reaction would be negative, as energy would be released during the reaction. The activation energy (Ea) would still be positive, as the reactants would still need to absorb energy to reach the transition state. However, the height of the curve would be lower for an exothermic reaction, indicating a lower activation energy.

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how the solubility product can be used to predict if a precipiate will form when two aqeuous solutions are mixed

Answers

The solubility product (Ksp) can be used to predict whether a precipitate will form when two aqueous solutions are mixed by comparing the ion product (Q) with the Ksp value.

When two solutions are mixed, the ions present in each solution may combine to form a new compound that has a low solubility, resulting in the formation of a precipitate. The solubility product constant (Ksp) is a measure of the maximum amount of a compound that can dissolve in water at equilibrium.

If the ion product (Q) of the solution is less than the Ksp value, then the solution is unsaturated and no precipitate will form. However, if Q is greater than Ksp, then the solution is supersaturated, and a precipitate will form until the concentration of ions in the solution reaches the solubility limit.

In other words, if Q>Ksp, then the solution is supersaturated, and precipitation will occur until Q=Ksp. If Q<Ksp, the solution is unsaturated, and no precipitation will occur. If Q=Ksp, the solution is at saturation and no further precipitation will occur.

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What 2 characteristics do ferns,club mosses, and horsetails share? How do these characteristics differ from those of mosses?

Answers

Ferns, club mosses, and horsetails are all vascular plants that reproduce by producing spores, and they share the following two characteristics:

Vascular tissue: These plants have specialized tissues for conducting water and nutrients throughout the plant. The vascular tissue is composed of xylem, which transports water and minerals from the roots to the rest of the plant, and phloem, which transports organic nutrients (such as sugars) from the leaves to the rest of the plant.

Spore production: These plants reproduce by producing spores, which are haploid (having one set of chromosomes) and can grow into new plants under favorable conditions.

In contrast, mosses are non-vascular plants that lack specialized tissues for conducting water and nutrients. Instead, they absorb water and nutrients directly from their surroundings through their leaves. Mosses also reproduce by producing spores, but they have a much simpler structure than ferns, club mosses, and horsetails. Mosses lack true roots, stems, and leaves, and they do not have a well-developed system for conducting water and nutrients throughout the plant.

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how is an unknown oxidation state of an element within a compound determined

Answers

Explanation:

You assign oxidation numbers to the elements in a compound by using the Rules for Oxidation Numbers.

The oxidation number of a free element is always 0.

The oxidation number of a monatomic ion equals the charge of the ion.

The oxidation number of H is +1, but it is -1 in when combined with less electronegative elements.

The oxidation number of O in compounds is usually -2, but it is -1 in peroxides.

The oxidation number of a Group 1 element in a compound is +1.

The oxidation number of a Group 2 element in a compound is +2.

The oxidation number of a Group 17 element in a binary compound is -1.

The sum of the oxidation numbers of all of the atoms in a neutral compound is 0.

The sum of the oxidation numbers in a polyatomic ion is equal to the charge of the ion.

__________________________________________________________

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you want to make 500 ml of a 0.20 m ha buffer with a ph of 5.25 using 1 m ha and and 1 m naoh. what volume (in ml) of naoh is required to make the buffer? the pka of ha is 5.75.

Answers

We need to add 17.78 mL of 1 M NaOH to 482.22 mL of 0.20 M HA to make 500 mL of a 0.20 M HA buffer with a pH of 5.25. The Henderson-Hasselbalch equation for a buffer is:

pH = pKa + log([A-]/[HA])

We are given that we want a pH of 5.25 and a pKa of 5.75 for the weak acid, HA. Let x be the volume of 1 M NaOH we need to add to the buffer.

First, we need to find the ratio of [A-]/[HA]:

10^(pH-pKa) = [A-]/[HA]

10^(5.25-5.75) = [A-]/[HA]

0.1778 = [A-]/[HA]

Next, we need to use the definition of molarity to find the moles of HA needed for the buffer:

M = moles / volume

0.20 M = moles / 0.5 L

moles = 0.1 mol HA

Since we know the ratio of [A-]/[HA], we can use this to find the moles of A- needed:

[A-] = 0.1778 [HA]

[A-] = 0.1778 mol/L * 0.1 L

[A-] = 0.01778 mol

Now we can use the definition of molarity again to find the volume of 1 M NaOH needed to add to the buffer:

M = moles / volume

1 M * x = 0.01778 mol

x = 0.01778 L = 17.78 mL

Therefore, we need to add 17.78 mL of 1 M NaOH to 482.22 mL of 0.20 M HA to make 500 mL of a 0.20 M HA buffer with a pH of 5.25.

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What is the normal boiling point pressure for water in kPa? kPa (exact number)

What is the normal boiling point pressure for water in mmHg? mmHg (exact number)

What is the normal boiling point temperature in Celsius of n-Octane? °C (whole number)

What is the normal boiling point temperature in Kelvin of Ethylene glycol? K (whole number)

At which temperature would ethylene glycol boil when the atmospheric pressure is 0.20 atm? °C (Whole number)

Answers

Answer: All the answers are given below.

Explanation:

The vapor pressure of water at 75°C is approximately 293 mmHg (whole number).

The vapor pressure of bromine at 300 K is approximately 240 mmHg (whole number).

The boiling point of mercury is 357°C at atmospheric pressure (760 mmHg), and the vapor pressure of mercury is 500 mmHg at a higher temperature than this. Therefore, the temperature at which the vapor pressure of mercury is 500 mmHg is greater than 357°C.

Diethyl ether's normal boiling point is 34.6°C, which is above the freezing temperature of water (0°C). At 0°C, the vapor pressure of diethyl ether is approximately 5.5 mmHg (whole number).

At a pressure of 50 mmHg, ethanol will boil at approximately 64°C (whole number).

The normal boiling point pressure for water is 101.3 kPa (exact number) at a temperature of 100°C.

The normal boiling point pressure for water is 760 mmHg (exact number) at a temperature of 100°C.

The normal boiling point temperature in Celsius of n-Octane is approximately 126°C (whole number).

The normal boiling point temperature in Kelvin of ethylene glycol is approximately 471 K (whole number).

To find the boiling point of ethylene glycol at a pressure of 0.20 atm, you can use the Clausius-Clapeyron equation. However, the equation requires knowing the vapor pressure of ethylene glycol at a known temperature. Without this information, it is not possible to calculate the boiling point.

What is an isolated system?

Answers

Answer:  An isolated system is a thermodynamic system that cannot exchange either energy or matter outside the boundaries of the system.

Explanation:

how does the strength of the attraction between water molecules and sodium and chloride ions compare

Answers

The strength of the attraction between water molecules and sodium and chloride ions is stronger compared to the attraction between water molecules themselves. This is due to the ion-dipole interaction between charged ions and polar water molecules.

The strength of the attraction between water molecules and sodium and chloride ions is generally stronger than the attraction between water molecules themselves. This is due to the following reasons:
1. Water molecules are polar, which means they have a partially positive charge on the hydrogen atoms and a partially negative charge on the oxygen atom.
2. Sodium and chloride ions are charged particles, with sodium ions having a positive charge and chloride ions having a negative charge.
3. When water molecules come into contact with sodium and chloride ions, the positive charge on the sodium ions attracts the negatively charged oxygen atoms in water molecules, and the negative charge on the chloride ions attracts the positively charged hydrogen atoms in water molecules.
4. This attraction between charged ions and polar water molecules is called ion-dipole interaction, which is stronger than the hydrogen bonding between water molecules.

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explain (in detail) how titrating to a dark pink color effects your calculated % acetic acid in your vinegar sample

Answers

It is crucial to carefully regulate the titration's endpoint since it might have a considerable impact on the computed percentage of acetic acid in a vinegar sample.

Titration is a typical laboratory procedure used to add a solution with a known concentration to an unknown solution until a chemical reaction is complete. Acetic acid is titrated using a standard solution of sodium hydroxide when using vinegar (NaOH). The solution will become too simple and the indicator will develop a dark pink hue if the titration is carried past the endpoint. This indicates that there has been an excessive amount of NaOH added to the solution, resulting in an underestimation of the proportion of acetic acid.

The solution will still be acidic if the titration is stopped before the endpoint, and the computed proportion of acetic acid will be excessively high. The endpoint of the titration will thus be indicated by a faint pink hue rather than a dark pink tint, hence it is crucial to titrate carefully and halt the titration at this point. This guarantees that the right quantity of NaOH was supplied and that the predicted acetic acid % is correct.

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the cis ketone a is isomerized to the trans ketone b with aqueous naoh. a similar isomerization reaction does not occur with the cis ketone c. explain this difference in reactivity. be sure to answer all parts.

Answers

When cis-ketone a is isomerized to trans ketone b with aqueous NaOH, it is because cis-ketones exist as a pair of rotamers that interconvert slowly at room temperature.

The two rotamers have different dipole moments, which makes them distinguishable from each other. This isomerization reaction does not occur with the cis-ketone c because there is no appreciable barrier to interconversion between the two rotamers. Thus, the two cis-ketone isomers are indistinguishable from each other in terms of dipole moment, making the reaction of the cis-ketone c unresponsive to the NaOH solution.

What is a cis-ketone, A ketone in which the carbonyl group is adjacent to an alkene group is referred to as a cis-ketone. The cis-ketone has a higher dipole moment than the trans-ketone due to the presence of the alkene group. As a result, the cis-ketone has a greater polarity than the trans-ketone, which has a lower dipole moment.

Trans and cis isomerismIn cis and trans isomerism, the isomers are chemically the same but differ in the way atoms are arranged in space. The terms "cis" and "trans" are used to describe this configuration in organic chemistry. In a molecule, cis isomers are those in which two substituents are on the same side of a bond, while trans isomers are those in which two substituents are on opposite sides of a bond.

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once a system is at a state of equilibrium, a shift from equilibrium may result by alteration of which of the following? opressure o composition o temperature all of the above

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A shift from equilibrium can result by alteration of any of the following: pressure, composition, or temperature. Option d is correct.

When a system is at equilibrium, it means that the rates of the forward and reverse reactions are equal and there is no net change in the concentrations of the reactants and products. However, if any of the conditions that affect the equilibrium are altered, such as the pressure, composition, or temperature, the equilibrium may shift to a new state.

For example, increasing the pressure may shift the equilibrium to favor the side with fewer moles of gas, while increasing the temperature may favor the endothermic or exothermic reaction depending on the direction of heat flow. Similarly, changing the composition by adding or removing reactants or products can also affect the equilibrium position. These changes in the equilibrium can be predicted and analyzed using the principles of chemical equilibrium. Hence option d is correct choice.

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write the balanced equation and use a correct mole ratio to calculate how many milliliters of 0.01154 m hcl are required to titrate 20.00 ml of 0.0125m ca(oh)2?

Answers

The balanced equation is written as

2HCl + Ca(OH)₂ --> CaCl₂+ 2H₂O. From using the mole ratio, the volume of 0.01154 M HCl needed to titrate 20.00 mL of 0.0125 M Ca(OH)₂ is equals to 43.3 mL.

Mole ratio is defined as a ratio between the number of moles of any two components in a balanced chemical reaction/equation. We have, two components Hydrochloric acid, HCl and calcium hydroxide, Ca(OH)₂ for reaction.

Volume of calcium hydroxide solution

V₁ = 20.00 mL = 0.020 L

Molarity of HCl, M₂ = 0.01154 M

Molarity of Ca(oh)₂, M₁ = 0.0125 M

Chemical reaction/equation for components,HCl + Ca(OH)₂-->CaCl₂+ H₂O

Balanced equation is written as

2HCl + Ca(OH)₂ --> CaCl₂+ 2H₂O

Now, mole ratio of HCl to Ca(OH)₂ is 2:1 that is moles of HCl are two times the mol of Ca(OH)₂ to form the respective products. Let V be the needed volume of hydrochloric acid to titrate Ca(OH)₂ solution. Using the molarity formula, Molarity of Ca(OH)₂ = moles of Ca(OH)₂/volume of Ca(OH)₂

=> 0.0125 mol/L = moles of Ca(OH)₂/0.02

=> moles of Ca(OH)₂ = 0.00025 moles

From mole ratio, moles of HCl are required to neutralize, Ca(OH)₂= 0.00025 moles Ca(OH)₂ (2 moles HCl/1 mole Ca(OH)₂ = 0.0005 moles

Now, using molarity formula for HCl,

M₂ = moles of HCl/Volume of HCl

=> 0.01154 Mol/L = 0.0005 moles/V

=> V = 0.0433 L = 43.3 mL ( 1L = 1000 mL).

Hence, required value of volume is 43.3 mL.

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how much work (in j ) is involved in a chemical reaction if the volume decreases from 4.10 to 1.12 l against a constant pressure of 0.801 atm ? express your answer to three significant figures and include the appropriate units.

Answers

if the volume decreases from 4.10 to 1.12 l against a constant pressure of 0.801 atm Then The work involved is 324.8 J

The change in volume is V₂ - V₁

∆V = 4.1 - 1.12 L

∆V = 2.98

∆V = 2.98 x 10⁻³ m³

∆V = 3 ×10⁻³ m³

The constant pressure is

p = 0.857 atm = 0.857*101325 Pa

p = 86836 Pa

By definition, the work done is

[tex]W = \int\limits pdV = 86836 \frac{N}{m²} * (3 ×10⁻³ m³)[/tex]

In physics, work is the energy transferred to or from an object via the application of force along a displacement. In its simplest form, for a constant force aligned with the direction of motion, the work equals the product of the force strength and the distance traveled. A force is said to do positive work if when applied it has a component in the direction of the displacement of the point of application. A force does negative work if it has a component opposite to the direction of the displacement at the point of application of the force.

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if 1g of magnesium and 1g of oxygen reacted, what will be left in the reaction vessel?

a)MgO only
b)MgO and Mg only
c)MgO and O2 only
d) MgO, Mg and O2

Answers

The answer is (a) MgO only, as all of the magnesium and oxygen react completely to form magnesium oxide, and there would be no unreacted magnesium or oxygen left in the reaction vessel.

What is Limiting Reagent?

The limiting reagent can be determined by comparing the mole ratios of the reactants and the coefficients in the balanced chemical equation for the reaction. The reactant that produces the least amount of product based on the stoichiometry of the balanced equation is the limiting reagent.

If 1g of magnesium (Mg) and 1g of oxygen (O2) reacted, they would combine to form magnesium oxide (MgO) according to the following chemical equation:

2Mg + O2 -> 2MgO

The molar mass of magnesium is 24.31 g/mol, while the molar mass of oxygen is 32.00 g/mol. Therefore, 1g of magnesium is equivalent to 0.041 mol, and 1g of oxygen is equivalent to 0.03125 mol.

According to the balanced equation, 2 moles of magnesium react with 1 mole of oxygen to form 2 moles of magnesium oxide. Thus, the limiting reactant in this reaction is oxygen because only 0.03125 mol of oxygen is available, whereas 0.082 mol of magnesium is available.

Using the limiting reactant, we can calculate the theoretical yield of magnesium oxide:

0.03125 mol O2 x (2 mol MgO / 1 mol O2) x (40.31 g MgO / 1 mol MgO) = 2.5 g MgO

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a vinegar sample requires 41.30 ml of a 0.1042 m naoh solution to reach the phenolphthalein endpoint. calculate the moles of acetic acid present in the vinegar sample.

Answers

The moles of acetic acid in the vinegar sample during the addition of NaOH is found to be 4.30 moles.

It is provided that vinegar sample is titrated in presence of phenolphthalein indicator to show the end point of the titration with 41.30 ml of 0.1042M NaOH.

The reaction goes like this,

CH₃COOH + NaOH → CH₃COONa + H₂O

So, as we can see, the moles of acetic acid are equal to the moles of NaOH in the solution.

So, the moles of NaOH are given as,

Moles = Molarity x volume

Moles = 0.1042 x 41.30

Moles = 4.30

So, the moles of acetic acid in the vinegar solution will be equal to the 4.30 moles.

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you have 20 gr of phosphorus that decays 5% per day. how long will it take for half the amount to decay?

Answers

The decay of phosphorus can be modeled using exponential decay, which is given by the equation:

N(t) = N0 × e^(-kt)

where N(t) is the amount of phosphorus remaining at time t, N0 is the initial amount of phosphorus (20 g in this case), k is the decay constant, and e is the base of the natural logarithm (approximately equal to 2.718).

The percentage decay per day is given as 5%, which means that the decay constant k can be calculated as follows:

k = ln(1 - 0.05)/(-1 day) ≈ 0.0513 day^(-1)

To find the time it takes for half the amount of phosphorus to decay, we can set N(t) equal to N0/2 and solve for t:

N(t) = N0/2 = N0 × e^(-kt)

e^(-kt) = 1/2

Taking the natural logarithm of both sides, we get:

-ln(2) = -kt

Solving for t, we get:

t = ln(2)/k ≈ 13.5 days

Therefore, it will take about 13.5 days for half of the initial amount of phosphorus (10 g) to decay.

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A chemical reaction has three reactants: A, B, and C. The reaction rate is given by R = [A][C]. What is the order of the reaction with respect to reactant B?

A) 0

B) 1

C) 2

D) 3

Answers

The correct answer for this question is d
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