which of the following is an indicator of a chemical reaction?

A. two different compounds is an indicator of a chemical reaction.

B. changing states of matter (solid to liquid)

C. decreasing in size.

D. increasing in temperature​

Answer:

In the 1930s a telephone-company engineer named Karl Jansky was trying to track down the cause of hissing static in phone lines when he discovered something strange. Radio energy from outer space was interfering with the phone signals. After learning about Janksy's discovery, a radio engineer named Grote Reber decided to investigate.

Explanation:

Addition of soda (Na₂CO₃) to the vitrifying mixture produces glasses with excellent optical properties.

Silica is the common name for the compound silicon dioxide, which consists of one silicon atom and two oxygen atoms. It is an important component of many rocks, sands, and clays, and is also found in many plants and animals. Silica is used in a wide variety of products, from beer and wine to pottery, glass, and paint. It is also used in building materials such as concrete and mortar, and as a food additive. Silica is also used to make silicon-based electronics such as computer chips.

Adding lime (CaCO₃) to the vitrifying mixture creates a jar that can be used to bake or store the liquid medicine.

Addition of alumina (Al₂O₃) to a mixture undergoing vitrification produces a glass that is insoluble in water.

Addition of borax (Na₂B₄O₇) to the mixture during vitrification allows glass to be produced at much lower temperatures.

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Answer:

weak

Explanation:

this is my best guess

Option B, Bonding pair-bonding pair, lone pair-bonding pair, lone pair-lone pair. The electrons in bonding pairs are repulsion held relatively closely together, and are involved in the formation of a chemical bond.

The repulsion between two bonding pairs is relatively weak, as they are attracted to the positively charged nuclei of the atoms they are bonding. The repulsion between a lone pair of electrons and a bonding pair of electrons is generally stronger than that between two bonding pairs because the lone pair is not involved in bonding and tends to be held further away from the nucleus, causing the electron cloud to be larger and thus a stronger repulsion because the two lone pairs are not involved in bonding, and are held relatively far away from the nuclei, causing the electron clouds to be larger and thus a stronger repulsion

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Answer:

The gas with molar mass 83.9 g is Krypton, Kr

Explanation:

We know that as per Ghram's law of diffusion,

r'/ r= square root (M/M')

0r [tex]\frac{r'}{r } =\sqrt{\frac{M}{M'} }[/tex]

Where

r= rate of diffusion of Cl2

r'= rate of diffusion of unknown gas= 0.920r

Also, M= molar mass of Cl2= 71 g/ mol

And, M'= molar mass of unknown gas which we have to find

Let us substitute the values in above equation

[tex]\frac{0.920r}{r } =\sqrt{\frac{71}{M'} }[/tex]

solving we get M' = 83.9 g/mol

Therefore,  the gas with molar mass 83.9 g is Krypton,Kr

Answer:

1.26 moles

Explanation:

Applying Avogadro's constant.

1 mole of every substance, has a particle of 6.02×10²³

From the question,

If,

1 mole of Neon contains 6.02×10²³ particles

Therefore,

x moles of Neon will contain 7.6×10²³ particles

x = (7.6×10²³)/(6.02×10²³)

x = 1.26 moles.

Hence the number of moles of Neon present is 1.26 moles

Answer:

decomposition reaction

Answer:

sure

Explanation:

Answer:

128.98 g/Mol

Explanation:

ΔTb = Kb * m * i

Where;

ΔTb = boiling point elevation

Kb = boiling point constant

m = molality of the solution

i = Van't Hoff factor

Hence;

Where molality = number of moles of solute/mass of solvent in Kg

Number of moles of solute = mass/Molar mass

So;

80.61 - 80.10 = 2.53 * 13g/M/0.5 * 1

Where M is the molar mass of the solute

0.51 = 2.53 * 13g/M/0.5

0.51 = 2.53 * 13/M * 1/0.5

0.51 = 32.89/M * 1/0.5

0.51 * 0.5 = 32.89/M

0.255 M = 32.89

M = 32.89/0.255

M= 128.98 g/Mol

Answer:

salt sodium chloride (NaCl)

16.5 g is the mass of sodium chloride that must be dissolved in the same mass of X to produce the same depression at freezing point.

Avogadro's number (6.022 x 1023) of molecules (or formula units) make up one mole of a substance (ionic compound). The mass of 1 mole of a chemical is indicated by its molar mass. It provides you with the number of grams per mole of a substance, to put it another way.

ΔT = Kc*W*i

Kc = cryoscopy constant of the solute X

W = molality of the solution

i = van't Hoff factor, For organic molecules, such as alanine, i = 1.

n = 45.8/89.09

n = 0.5141 mol

W = 0.5141/1.2 = 0.4284 mol/kg

So, Kc of X is:

4.10 = Kc*0.4284*1

Kc = 9.57 °C.kg/mol

So, if now sodium chloride is added to X, and the temperature change is the same, and i = 1.82:

4.10 = 9.57*W*1.82

W = 0.2354 mol/kg

The number of moles of the solute is then:

W = n/1.2

0.2354 = n/1.2

n = 0.2825 mol

The molar mass of sodium chloride is 58.44 g/mol, thus the mass is the molar mass multiplied by the number of moles:

m = 58.44*0.2825

m = 16.5 g

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Design extra reinforcements in the building's windows so that they can withstand the vibrations from sonic booms.

What are Sonic booms?

Sonic booms are shock waves created when an object, such as an aircraft or spacecraft, travels through the air at a speed faster than the speed of sound (approximately 767 mph). Sonic booms generate a loud noise that can be heard over long distances. Sonic booms can cause property damage and are hazardous to people's hearing.

Extra reinforcements in the building's windows can help to absorb the shock of sonic booms. This is done by adding additional layers of materials such as glass, plastic, rubber, or metal to the window frame. These materials will help to dampen the vibrations from sonic booms, reducing the noise and preventing damage to the windows. Additionally, window seals can be installed to reduce air infiltration, further helping to protect the windows from the vibrations of sonic booms.

Hence, Option C is correct.

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The complete lewis structure is shown in the below figure by adding lone pairs and formal charges.

Assign the valence electrons to each atom as dictated by the periodic table placing one electron at each compass direction and then pairing them only after the first four until you have place all of the atom’s valence electrons. (See the Roman numeral above the group/column it is in.)

Arrange the remaining atoms around the central atom and join them to the central atom by a single bond. The more electronegative atoms are typically farther away from the center and attaching hydrogen last is advised.

Lone electrons (not lone pairs) indicate an ability to form more covalent bonds, resulting in either double or triple bonds. Their presence or the lack of a full octet on any atom indicates there is a better Lewis structure.

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Answer:

38.51g NaOH

Explanation:

NaOH=39.907 g/mol

0.965 mol NaOH X 39.90g NaoH/1 mol NaOH= 38.51 g NaOH

Cribbing is the tool we use prior to making your first extrication cut in the vehicle

Before making the first extrication cut, it is important to stabilize the vehicle to prevent it from moving and to ensure the safety of the individuals involved in the extrication process. One tool that is commonly used to stabilize a vehicle during extrication is a set of stabilizing struts, also known as cribbing. Cribbing is a set of wooden or composite blocks that are placed under the vehicle to support it and prevent it from moving. The cribbing is typically placed at strategic points, such as the frame of the vehicle or the wheels, to provide a stable base for the vehicle.Additionally, other tools like wheel chocks, jacks, and air bags may be used to provide additional support and stability. The extrication team will assess the situation and choose the most appropriate tool to stabilize the vehicle.

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Explanation:

Atoms are tiny spheres that cannot be divided

Maybe for sure its element number as five and two in for as Number of electrons in each level?  

Answer:

Explanation:

Aluminium hydroxide is amphoteric. 3 HCl + Al(OH)3 → AlCl3 + 3 H2O. In bases, it acts a Lewis acid by taking an electron pair from the hydroxide ions: Al(OH)3 + OH− → Al(OH)

Answer: rytesttrt5rtr

Explanation:

4 ATP molecules are directly generated in the Krebs cycle when 2 molecules of glucose are oxidized

The Krebs cycle,  TCA cycle or the citric acid cycle, is a series of enzyme-catalyzed reactions occurring  in the mitochondrial matrix and involves the oxidation of acetyl-CoA.

The acetyl group of acetyl-CoA is oxidized to make two molecules of CO2 in a succession of eight steps, while also producing one ATP. Additionally, reduced high-energy molecules like NADH and FADH2 are created.

Each glucose molecule produces two acetyl-CoA molecules, the Krebs cycle must  move twice for one glucose molecule to produce the four CO2, six NADH, two FADH2, and two ATPs.

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Answer: 351

Explanation: From °C to kelvin we do

K=273+°C

From Kelvin to °C we do

°C=K-273 or -273+ K

The type of reaction is a double replacement reaction. In a double replacement reaction, the positive ions of two compounds switch places to form two new compounds.

The balanced chemical equation for the reaction between magnesium and lead(II) nitrate is:

Mg(s) + Pb(NO3)2(aq) -> Mg(NO3)2(aq) + Pb(s)

In this equation, the magnesium and lead ions switch places to form the new compounds magnesium nitrate and lead. The coefficients in front of the compounds indicate the number of moles of that substance that are involved in the reaction. The subscripts indicate the number of atoms of each element in each compound.

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Answer:

Option 2:

The warmth of the spoon is conducted to the ice cream making it easier to scoop out.

Explanation:

Conduction refers to the transfer of heat from a hotter body to a cooler one, by virtue of physical contact between the two bodies. This is opposed to radiation, where there does not need to be any contact between the two bodies before heat con flow.

The warm spoon, once it has physical contact with the cool ice cream, it loses some of its heat to the ice cream, warming it up, making it easier to scoop up.

Answer:

tells you by mass what percent of each element is present in a compound.

Explanation:

The atomic number is the number of protons in the nucleus of an atom and it directly affects the properties of an element. The atomic number also determines the element's place in the periodic table, which allows us to predict the properties of an element based on its atomic number.

As the atomic number increases, the number of protons in the nucleus increases and so does the atomic number. This increase in protons also increases the number of electrons in the atom. The number and arrangement of electrons in an atom directly affect its chemical behavior and thus the properties of the element.

The atomic number also determines the element's position on the periodic table, and elements with similar atomic numbers have similar chemical and physical properties. For example, elements in the same vertical row (group) have similar chemical properties, and elements in the same horizontal row (period) have similar electronic configurations of their atoms.

The atomic number also affects the reactivity of an element. Elements with lower atomic numbers tend to be more reactive than elements with higher atomic numbers.

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Answer: There are 0.00054 moles of silane gas (SiH4) are present in 8.68 mL measured at 18 0C and 1.50 atm.

Explanation:

Given: Volume = 8.68 mL (1 mL = 0.001 L) = [tex]8.68 \times 10^{-3} L[/tex],    

Temperature = [tex]18^{o}C = (18 + 273) K = 291 K[/tex],

Pressure = 1.50 atm

The ideal gas formula is as follows.

PV = nRT

where,

P = pressure

V = volume

n = no. of moles

R = gas constant = 0.0821 L atm/mol K

T = temperature

Substitute the values into above formula as follows.

[tex]PV = nRT\\1.50 atm \times 8.68 \times 10^{-3} L = n \times 0.0821 L atm/mol K \times 291 K\\n = \frac{1.50 atm \times 8.68 \times 10^{-3} L}{0.0821 L atm/mol K \times 291 K}\\= \frac{0.01302}{23.8911}\\= 0.00054 mol[/tex]

Thus, we can conclude that there are 0.00054 moles of silane gas (SiH4) are present in 8.68 mL measured at 18 0C and 1.50 atm.

Answer: Both are only physical changes

Both converse mass

Explanation: the first two ones r correct

Students as a chemical reaction that absorbs thermal energy for the design of cold packs for the treatment of injuries can combine manganese oxide (MnO2) with hydrogen peroxide (H2O2)

By controlling the amounts of the reactants they can control the temperature, keeping it between 0 °C and 4 °C for 20 minutes or more.

This type of chemical reaction is called endothermic, because energy is absorbed in the form of light or heat, causing the resulting products to have higher energy than the reactants.

The most widely used endothermic chemical reaction in the treatment of injuries is the melting of ice, at least in warm environments, which occurs according to the following reaction:

H2O (s) + Energy ----- H2O (l)

The effect of an endothermic reaction is absorbs heat energy and in the case of manganese oxide the following decomposition occurs:

MnO2 (s) → MnO (s) + ½ O2 (g); ∆HR = 134kJ

Students can design cold packs for treating injuries with manganese dioxide bcause it breaks down into two products, manganese oxide and oxygen, making the enthalpy greater than zero (∆HR > 0).

MnO2 is a solid between gray and black in color and is present in minerals such as pyrolusite and nsutite, when combined with hydrogen peroxide it acts as a catalyst so that it accelerates chemical reaction

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Answer:

in the lead strip the will be no change and no reaction. this is job salvation that is made when magnesium powder and lead to our heater together