Answer:
A. 28 years
Explanation:
Applying,
R = R'(2ᵃ/ⁿ).............. Equation 1
Where R = Original sample, R' = Sample left after decay, a = Total time taken to decay, n = half life.
From the question,
Given: R = 12 g, R' = 6 g, a = 28 years.
Substitute into equation 1 and solve for n
12 = 6(2²⁸/ⁿ)
12/6 = 2²⁸/ⁿ
2²⁸/ⁿ = 2
Equation the base,
28/n = 1
n = 28 years.
Hence the half-life is 28 years
explain what happens during a solar eclipse
Answer:
a solar eclipse is when the moon moves between the earth and the sun, so the moon casts a shadow on the earth
Explanation:
Answer:
the moon gets in the way of the sun and cast a shadow onto earth
Explanation:
Consider the positions of barium (Ba), sulfur (S), silicon (Si), and calcium (Ca) on the periodic table. The atoms of which element require the least amount of energy to give up an electron when forming chemical bonds?
barium
sulfur
silicon
calcium
According to the electronic configuration and shielding effect along a group barium requires the least amount of energy to give up an electron when forming chemical bonds.
What is electronic configuration?
Electronic configuration is defined as the distribution of electrons which are present in an atom or molecule in atomic or molecular orbitals.It describes how each electron moves independently in an orbital.
Knowledge of electronic configuration is necessary for understanding the structure of periodic table.It helps in understanding the chemical properties of elements.
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Answer:
A. Barium
Explanation:
The higher the metallic character, the less energy needed to give up an electron.
The metallic character is higher in the higher period numbers and in the lower group numbers. Out of all the elements listed, Barium would require the least amount of energy.
Antarctica contains 26. 8 million cubic kilometers of ice. Assume that the average temperature of this ice during the summer months is20 ∘C If all of this were heated to 4 ∘C and melted to form water, what volume of liquid water would form?
Volume of liquid water would be approximately 24 million km³.
Volume(V) of ice at 20° is;
Vi = 26.8×10⁶ km³
Density is depend upon the mass and volume
∴ p =m/v
where; p = Density
m = Mass
v = Volume
Density of ice p(i) = 0.92g /cm³
Density of water at 4°C is;
p(w) = 1g/cm³
If ice is melt then,
mass(m) of water = mass(m) of ice
p(w) = p(i)
V = p(i)/p(w)
0.92g / cm³/1g/cm³×26.8×10⁶ km³
24.5 ˣ 10⁶ km³
≈24 million km³
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A student performs an experiment several times to determine the enthalpy of combustion of naphthalene, an organic compound with the formula C10H8, and collects the following data: −5181. 6kJmol, −5181. 9kJmol, −5183. 5kJmol, −5180. 1kJmol, and −5184. 2kJmol. What is the relative standard deviation (RSD) for this set of data? Give the answer as a positive number
The relative standard deviation (RSD) for this set of data is 9.98.
What is the combustion enthalpy in kJ/mol?The enthalpy change that occurs when 1 mole of a substance burns (combines vigorously with oxygen) under standard state conditions is known as the standard enthalpy of combustion also known as the heat of combustion. The enthalpy of combustion of ethanol, for instance, is 1366.8 kJ/mol.
Total = -5182.6 - 5181.9 - 5183.5 - 5180.1 - 5184.2
Total = -25912.3
number of items = 5
mean = total sum / number of items
mean = -25912.3/5
mean = -5182.46
[tex]x_{i}[/tex] [tex]x_{i}[/tex]-µ ([tex]x_{i}[/tex]-µ)²
-5181.6 0.86 0.7396
-5181.9 0.3 0.09
-5181.5 -0.1 0.01
-5181.1 -0.5 0.25
-5181.2 -0.4 0.16
∑ ([tex]x_{i}[/tex]-µ)² = 1.2496
Standard deviation = √∑ ([tex]x_{i}[/tex]-µ)² /x
Standard deviation = √1.2496/5
Standard deviation = 0.499
Relative standard deviation = S x 100/x
Relative standard deviation = 0.499 ×100/5
Relative standard deviation = 9.98
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What is the cause of periodic repetition of properties of elements?
The periodic repetition of properties of elements is due to the regular arrangement of electrons in the atoms of those elements. This regular arrangement is known as the "periodic table" of elements. This is due to the behavior of electrons in atoms and the increasing number of valence electrons as atomic number increases, resulting in a regular pattern of electron configurations and properties.
Elements are arranged in the periodic table according to increasing atomic number. Elements in the same vertical row (group) have similar chemical and physical properties, and elements in the same horizontal row (period) have similar electronic configurations of their atoms.
The reason for this repeating periodic property is the behavior of the electrons in the atoms. As the atomic number increases, the number of protons in the nucleus increases, and the number of electrons in the atom increases. These electrons occupy different energy levels or shells around the atomic nucleus. The outermost shell electrons, the so-called valence electrons, are responsible for the chemical behavior of atoms and participate in chemical bonds. As the atomic number increases, the number of valence electrons in the atom increases. This results in a regular pattern of electron configurations and thus a regular pattern of properties.
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Consider the feedback loop that occurs when you je rk your hand away from something hot. How does this reflex help to maintain homeostasis?
Considering the feedback loop that occurs when you quickly remove your hand away from something hot, this reflex helps to maintain homeostasis by ensuring that the body is free from danger and thus maintains the internal condition of the body.
What is homeostasis?The stable internal, external, and chemical conditions that are maintained by living systems are known as homeostasis. In order for the organism to function at its best, a number of factors, including body temperature and fluid balance, must be maintained within predetermined ranges.
The body's reflexes help to maintain homeostasis in the body such as heart rate, breathing rate, blood pressure, and digestion.
Some reflexes that maintain homeostasis in the body include:
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I’ll give brainliest if correct please help!
Answer:
the first one is the answer is to the question
What is the evidence for Darwin's theory of evolution?
The evidence for Darwin's theory of evolution is the consistency of the sequence of fossils from early to recent.
Changing populations and species of organisms are at the heart of biological evolution. The British naturalist Charles Darwin is most likely the first individual that comes to mind today when we discuss evolution. The biological evolution via natural selection theory was put out by British biologist Charles Darwin. Darwin believed that species change over time, give rise to new species, and descended from a single ancestor through the process of evolution. Charles Darwin's theory of evolution is known as natural selection. Animals with heritable qualities that aid in survival and reproduction will often generate more offspring than their contemporaries due to the limited resources in nature, increasing the frequency of such traits through subsequent generations.Populations change throughout time through natural selection, becoming increasingly adapted to their surroundings. Natural selection is reliant on the environment and necessitates the presence of heritable variation within a population.
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A nurse is caring for a client who has a serum potassium level of 3.1 mEq/L. Which of the following actions should the nurse take first?
A) Obtain an ECG.
B) Administer oral potassium
C) Encourage potassium-rich foods
D) Monitor I & O
To solve this we must be knowing each and every concept related to potassium level. Therefore, the correct option is option A that is Obtain an ECG.
What is potassium level?This condition is known as hyperkalemia, or excessive potassium. The Mayo Clinic states that the potassium level in blood should be between 3.6 to 5.2 millimoles a liter (mmol/L).
Critically high potassium levels are those over 5.5 mmol/L, while levels above 6 mmol/L could be lethal. A nurse is caring for a client who has a serum potassium level of 3.1 mEq/L. She should Obtain an ECG.
Therefore, the correct option is option A that is Obtain an ECG.
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2.278 x 10^-4 mol of an unidentified gaseous substance effuses through a tiny hole in 95.70 s. Under identical conditions, 1.738 x 10 ^-4 mol of argon gas takes 81.60 s to effuse. What is the molar mass of the unidentified substance
The unnamed material has a molar mass of 32 grammes per mole, and it exhales 2.278 x 10-4 molecules of an unknown gas through a minute hole in 95.70 seconds.
It takes 81.60 s for 1.738 x 10 -4 mol of argon gas to effuse under the same circumstances. The definition of molar mass is the mass in grammes of a mole of a specific chemical. The term "mole" refers to any material or compound that includes the Na number of atoms, molecules, or ions, where Na is the Avogadros number and Na = 6.023 1023. A molecule's total atomic mass expressed in grammes per mole is known as its molar mass. to figure out a molecule's molar mass
R1/R2 equals (M2/M1)1/2 2.38*10-6/2.1299*10-6 = sqrt(40/M1).
40 M1/M1 = 1.25 M2/M2 = 32 gm/mole
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How many grams are in 0.89 moles of CaCI2
0.0080 grams are in 0.89 moles of CaCI₂.
What is mole ?
The mole (M) is defined as it contain exactly 6.023 × 10²³ elementary entities present in it. 1 mole is exactly equal to the 6.023 × 10²³ elementary entities.
We can solve the above problem as follows;
So,
1 Mole of substance = Molar mass of the substance.
The given compound named is Calcium Chloride.
Then,
Molar mass of Calcium chloride = 1 mole
Molar mass of CaCl₂ = 40 + 2 × 35.4
= 110.9g/mol
Therefore,
110.9 grams of CaCl₂ = 1 mole
1 gram of CaCl₂ = 1 / 110.9
0.89 grams of CaCl₂
= 1 / 110 × 0.89
= 0.0080 grams
Thus, 0.0080 grams are in 0.89 moles of CaCI₂.
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5) Bob was walking home from school at a rate of 2 miles per hour at 3:30 and at 4:00, he
was walking 4 miles per hour. What was his rate of acceleration during that time? (Hint:
Him needs to be in hours, not minutes.)
Answer:
Explanation:
Applying,
at ph=0, the net charge on a polypeptide will be negative.
a. true
b. false
False. A polypeptide will have a negative net charge at ph=0.
A polypeptide is what?A peptide is a small, chemically bound chain of amino acids, usually between two and fifty amino acids (called peptide bonds). A polypeptide is a longer (51 or more amino acids) chain of connected amino acids. One or more polypeptides are used to create the proteins that are produced inside of cells.
What role does the polypeptide play?Polypeptides. Proteins are created by joining several amino acids together to form polypeptides. The coupling of two or so more polypeptides results in the formation of proteins, after which they are folded into the appropriate shape.
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A drum of hight 1.5m
is filled with water (density 100 kg/m^3). Find
the pressure of water at the bottom of drum.
Answer:
pressure= density × gravity × height
Explanation:
100 × 10 × 1.5= 1500 pa
What is the group number of the element in the periodic table?
a
1
b
2
c
13
d
15
The group number of the element in the periodic table is equal to 15 as it has five valence electrons. Therefore, .option D is correct.
What is a valence electron?Valence electrons can be explained as the electrons occupying the outer shell of an atom while the electrons placed in the inner shell are known as core electrons. Lewis structures of the elements can be helpful to calculate valence electrons and know the types of bonds.
Valence electrons can be filled in different shells, causing interaction between atoms and leading to the formation of chemical bonds.
The five elements have five electrons in their valence shell therefore it belongs to nitrogen family. The group number can be calculated as 10 + 5 = 15
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What happens to the reactivity when we move from left to right in the periodic table?
The metallic qualities drop and the non-metal characteristics rise as we progress from left to right, which results in a decrease inside the reactivity of such elements.
Metal reactivity is influenced by their propensity to lose electrons. The valence electrons could be simply eliminated as the atomic size grows, resulting in the formation of positive ions. As we proceed down the periodic table, the atomic size of metals gets bigger. The propensity to acquire electrons determines how reactive non-metals are.
Metal fosters strong down groups and declines across intervals from left to right. Indicators of nonmetallic properties rise from left to right and fall down groupings. Nonmetal reactivity goes up groups as well as down groups, increasing from left to right.
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A gas occupies 3.00 L at standard temperature. The volume at 350 C is 6.84 L.
True
False
Answer:
TRUE
Explanation:
Standard temperature is 273K and 350°C is 623K.
V/V' = T/T'
3/6.84 = 273/T'
T' = (273×6.84)/3
=> T' = 623K
So it is true.
During the chemical reaction that takes place inside a hot pack, is energy being released to the surroundings or taken in from the surroundings and
why?
Energy is taken in because all chemical reactions take in energy.
Energy is released because the temperature of the surroundings increases.
Energy is taken in because the temperature of the surroundings increases.
Energy is released because all chemical reactions release energy.
2
Answer:
Energy is released because the temperature of the surroundings increases.
Explanation:
"Energy is released because the temperature of the surroundings increases" is true because when the temperature of the hot pack increases, that means that energy (heat/thermal) is being released.
"Energy is taken in because the temperature of the surroundings increases" is false because energy is actually being released in this chemical reaction.
"Energy is taken in because all chemical reactions take in energy" is false because energy is being released in this reaction and not all chemical reactions absorb energy.
"Energy is released because all chemical reactions release energy" is false because not all chemical reactions release energy.
Would greatly appreciate the help
9.0 mol Na2S reacts with 8.0 mol
CuSO4 according to the equation below:
Na2S + CuSO4
→
Na2SO4 + CuS
Considering only the 8.0 mol CuSO4,
how many moles of CuS form?
? mol CuS
Round your answer to the tenths place.
Mole measure the number of elementary entities of a given substance that are present in a given sample. Therefore, 8.0 mol of CuS form when 8.0 mol CuSO[tex]_4[/tex] reacts.
What is mole?The SI unit of amount of substance in chemistry is mole. The mole is used to measure the quantity or amount of substance. We know one mole of any element contains 6.022×10²³ atoms which is also called Avogadro number. The stoichiometry represents the number of moles.
Na[tex]_2[/tex]S + CuSO[tex]_4[/tex]→ Na[tex]_2[/tex]SO[tex]4[/tex] + CuS
moles of Na[tex]_2[/tex]S =9.0 mol
moles of CuSO[tex]_4[/tex]=8.0 mol
Since CuSO[tex]_4[/tex] is limiting reagent
moles of CuS=8.0 mol
Therefore, 8.0 mol of CuS form when 8.0 mol CuSO[tex]_4[/tex] reacts.
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PLZ HELP ASAP!!!!!
Aluminum oxide (Al2O3) is extracted from bauxite and provides the major source of aluminum in the world. What mass of pure aluminum can be extracted from 655 g aluminum oxide?
A. 262 g
B. 309 g
C. 346 g
D. 368 g
The mass of the pure aluminum that can be extracted from 655 g of aluminum oxide is equal to 346 g. Therefore, option (C) is correct.
What is the balanced chemical equation?A balanced equation in which the number of atoms of each element should be same on the both sides of the equation. From the law of conservation of mass, the total mass of the elements on the reactant side as well as the product side should be equal in a balanced chemical equation.
The balanced chemical equation of the decomposition of aluminum oxide:
2Al₂O₃ (s) → 4 Al (s) + 3O₂ (g)
Given, the mass of the aluminum oxide = 655 g
The number of moles of aluminum oxide = 655/101.96 = 6.42 mol
2 moles of aluminum oxide form aluminum = 4 mol
Then 6.42 mol aluminum oxide form aluminum = (4/2) ×6.42 = 12.85 mol
The mass of the aluminum can be extracted = 12.84 ×27 = 346.9 g
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what are the two quantities in this module for which we will develop unit factors to do dimensional analysis with chemical substances?
The two quantities in this module for which we will develop unit factors to do dimensional analysis with chemical substances are volume and mass.
What is Volume?
Volume is a measure of the amount of three-dimensional space occupied by an object or substance. It is often measured in liters, cubic centimeters, or cubic meters. Volume is used to measure the capacity of a container, the size of an object, or the amount of liquid or gas in a given space. It is also used to determine the mass of an object, as the density (mass per unit volume) is often known.
The two quantities of volume and mass are important for doing dimensional analysis with chemical substances because they help to measure the amount of a substance in different units. Volume is important for measuring the quantity of liquid substances, and mass is important for measuring the quantity of solid substances. Both of these quantities are necessary for accurate and precise measurements of chemical substances, making them essential for dimensional analysis.
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Ammonia solution used for cleaning has a pH of 8.5. So the solution is____
a) acidic
b) neutral
c) basic
Answer: C
Explanation: Basic 8- 14
75g of a potato chip are burned in a calorimeter that contains 2L of water initially at 297K. After the combustion, the temperature rises 12oC. How much heat is involved per gram of potato chip burned
The amount of heat involved per gram of potato chip burned is 8388J when a 75g of a potato chip are burned in a calorimeter that contains 2L of water initially at 297K.
Given mass of potato chips burned = 75g
Mass of water (m) = 2L = 2000g
Initial temperature (T1) = 297K - 273 = 24oC.
Final temperature after combustion (T2) = 12oC
We know that q = mC∆T where q is heat and C is specific heat of water = 4.2J/g/oC.
q = 2000 x 4.2 x (24-12)
q = 8388J
Hence the heat evolved per gram of potato chip burned is 8388J
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burning of a paper
chemical change or physical change
Answer:
chemical change
Explanation:
Ash is formed as result of burning of paper which is a new product. Chemical change a new substance must form.
Answer: chemical change
Explanation: A chemical change is irreversible and also leads to the formation of a new substance. Burning paper leads to the formation of Ash. And a burnt paper can't be made to return to it's original form.
Which one of the following atoms or ions has the largest radius?
A. K+ B. Cl– C. K D. Na
Option (c) is correct. K atom has the largest radius as the atomic size decreases from across the period and potassium is located in the start of period 3 in the periodic table.
According to the Periodic table, atomic size decreases when going from left to right across a period. Atomic size increases when going from top to bottom down a group. If you look at elements that are located in the same group, potassium will have a larger atomic radius when compared with sodium and chlorine. Since potassium is located at the start of period 3, potassium will have a larger atomic radius and thus the largest atomic radius of the four given atoms. Atomic radii vary in a predictable way across the periodic table. From top to bottom in a group, orbitals corresponding to higher values of the principal quantum number (n) are being added, which are on average further away from the nucleus, thus causing the size of the atom to increase.
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How did the experiement with boiling water compare with the experiment in which magnesium was added to hydrochloric acid
In the experiment with boiling water and the experiment in which magnesium was added to hydrochloric acid both resulted in gas formation.
Hydrochloric acid and magnesium in a balanced chemical reaction
[tex]MgCl_{2}[/tex] + [tex]H_{2}[/tex] = Mg + 2HCl (g).
A gas is hydrogen . This reaction is exothermic (energy is released). New compounds are being produced due to chemical change.
Nothing new is created when water is heated to a boil. Heat is added in this endothermic reaction. Gas is steam. Both experiments a gas is released. One is a chemical change the other is a physical change. One is exothermic while other is endothermic.
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Consider the orbital diagram
shown. Which electron rule is
broken in the diagram?
1
1s 2s
2p
A. Aufbau Principle
B. Hund's Rule
C. Pauli Exclusion Principle
Answer: Aufbau Principle
Explanation:
Aufbau Principle - states that lower energy orbits must be completely filled before moving onto a higher energy level
Hund's Rule - pairing rule; all boxes in the level must be given one arrow before adding a second arrow
Pauli Exclusion Principle - each box must contain two arrows pointing in different directions
This question doesn't completely fill the 1s level before moving onto the next 2s level. Therefore, the digram violates the Aufbau Principle.
Show all your work and make sure to label all the numbers with the correct units if you do, I will give you brainliest, 5 stars, and a thank you:
A: A sample of sulfuric acid has a mass of 15.0 g. How many molecules are in this sample?
B: How many moles of sulfuric acid are present in 45 g of this sample?
C: How much would a .750 mole sample of Ammonium sulfate weigh?
D: What is the mass percent of hydrogen in this sample?
how many chlorine atoms are in 0.650 mol of ca(clo4)2?
Chlorine atoms that are present in 0.650 mol of ca(clo4)2 is : 7.83 *10^23.
What is meant by molar mass?Mass in grams of 1 mole of the substance is called the molar mass of a substance. We can obtain a substance's molar mass by summing the molar masses of its component atoms. We can use the calculated molar mass to convert between mass and number of moles of a substance.
As we know, one mole of any atom is equivalent to the Avogadro's number or 6.02 x 10²³ particles.
0.650 * 6.023 * 10^23 * 2
= 7.83 *10^23 chlorine atoms.
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How many neutrons are there in 14 gram of c14?
48×10²³ neutrons are there in 14 gram of C14
Any material that is totally composed of the same kinds of atoms is said to be an element. For instance, the element carbon is made up entirely of carbon atoms. The number of protons in an atom is indicated by the element's atomic number. The quantity of protons and electrons inside a neutral atom must match.
Neutron in 14 grams of C14 can be calculate as follows:
Mass number (or atomic weight) of ₆C¹⁴ is 14.
we know that Avogadro number =6×10²³
The number of neutrons in 12g of ₆C¹⁴ can be calculate by multiplying the number of neutron to the avogadro number
The total amount of protons and neutrons makes up mass. There will thus be = 14 - 6 = 8 neutrons.
neutron = (A−Z)×6×1023=(14−6)×6×10²³=48×10²³
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