Question 1

Which statement best describes the Law of Conservation of Mass?

Accepted Answer

The Law of Conservation of Mass states that matter cannot be created or destroyed, only transformed from one form to another. Therefore, in a chemical reaction, the total mass of the reactants must be equal to the total mass of the products. This is the best described by answer choice D.

Question 2

The unbalanced equation for the combustion of octane, a component of gasoline, is shown below.What would be the coefficient of carbon dioxide once the equation is balanced? C₈H₁₈(l) + O₂(g) → CO₂(g) + H₂O(l)

Accepted Answer

To balance the equation, we need to make sure that the number of atoms of each element is the same on both sides. We can start by balancing the carbons, which are only present in octane and carbon dioxide. There is 1 carbon atom in octane and 1 in carbon dioxide, so the coefficient of carbon dioxide should be 1. Next, we balance the hydrogens, which are present in octane, carbon dioxide, and water. There are 18 hydrogen atoms in octane, 0 in carbon dioxide, and 12 in water. To balance the hydrogens, we need to add a coefficient of 6 to water, which gives us a total of 6x2=12 hydrogen atoms. Finally, we balance the oxygens, which are present in oxygen gas, carbon dioxide, and water. There are 12 oxygen atoms in oxygen gas, 2 in carbon dioxide, and 6 in water. To balance the oxygens, we need to add a coefficient of 8 to oxygen gas, which gives us a total of 8x2=16 oxygen atoms. Therefore, the balanced equation is:

2C8H18(l) + 25O2(g) → 16CO2(g) + 18H2O(l)

The coefficient of carbon dioxide is 16.

Question 3

Which notation properly indicates how two molecules of diatomic oxygen would be represented in a chemical equation?

Accepted Answer

The correct notation for two molecules of diatomic oxygen in a chemical equation is to use the coefficient 2 in front of the molecular formula for oxygen, which gives "2O2". Choice A is not a recognized notation. Choice B uses a subscript indicating 4 oxygen atoms, which is not correct for two molecules of diatomic oxygen. Choice D uses two separate molecular formulas without a coefficient, which does not indicate that two molecules are present.

Question 4

The chemical equation below is not balanced.Balance the equation, then determine which statement concerning the balanced equation is TRUE. KClO₃(s) → KCl(s) + O₂(g)

Accepted Answer

The answer of The chemical equation below is not balanced.Balance...

Question 5

Hydrogen fluoride will react with glass (silicon dioxide, SiO₂) according to the equation below.What mass of HF is required to react completely with 16.0 g of glass?[Molar masses: Si, 28.09 g/mol; F, 19.00 g/mol; H, 1.01 g/mol; O, 16.00 g/mol] 4HF(g) + SiO₂(s) → SiF₄(g) + 2H₂O(g)

Accepted Answer

First, we need to balance the chemical equation:

4HF(g) + SiO2(s) → SiF4(g) + 2H2O(g)

The balanced equation tells us that 4 moles of HF are required to react completely with 1 mole of SiO2.

Next, we convert the given mass of SiO2 to moles:

16.0 g SiO2 × (1 mol SiO2/60.08 g SiO2) = 0.266 mol SiO2

Now, we can use the mole ratio from the balanced equation to calculate the moles of HF needed:

0.266 mol SiO2 × (4 mol HF/1 mol SiO2) = 1.06 mol HF

Finally, we convert the moles of HF to grams using the molar mass of HF:

1.06 mol HF × 19.00 g HF/mol = 20.1 g HF

Therefore, the mass of HF required to completely react with 16.0 g of SiO2 is 20.1 g. The closest answer choice is B) 21.3 g.

Question 6

How many molecules of water are present in a 5.65 mole sample of water?

Accepted Answer

One mole of any substance contains Avogadro's number (6.022 × 10^23) of particles. Therefore, 5.65 moles of water contain:

5.65 mol × 6.022 × 10^23 mol^-1 = 3.40 × 10^24 molecules of water

Therefore, the answer is (C) 3.40 × 10^24 molecules.

Question 7

Consider the chemical equation shown below.How many moles of oxygen gas are needed to react with hydrogen to form one mole of water? 2H₂(g) + O₂(g) → 2H₂O(l)

Accepted Answer

The balanced chemical equation for the formation of water from hydrogen and oxygen is $2H_2(g) + O_2(g) \rightarrow 2H_2O(l)$. This shows that 1 mole of $O_2$ is needed to react with 2 moles of $H_2$ to produce 2 moles of $H_2O$. Therefore, to produce 1 mole of $H_2O$, 0.5 mole of $O_2$ is needed.

Question 8

What is the mass of 4.00 moles of helium, the gas commonly used to fill party balloons and lighter-than-air ships?

Accepted Answer

The molar mass of helium (He) is 4.00 g/mol. Therefore, the mass of 4.00 moles of helium is 4.00 g/mol x 4.00 mol = 16.0 g. Therefore, the correct choice is D, which is the only option that gives the correct value for the mass of 4.00 moles of helium.

Question 9

Aluminum metal and oxygen gas are produced when aluminum oxide is heated at high temperature.Which statement concerning this chemical change is true?

Accepted Answer

This reaction is a decomposition reaction because aluminum oxide is breaking down into aluminum metal and oxygen gas.

Question 10

Which symbol, often found in chemical equations, indicates that a substance is dissolved in water?

Accepted Answer

The symbol (aq) stands for "aqueous," indicating that a substance is dissolved in water.

Question 11

The fluoride rinse in dental offices usually contains sodium fluoride.Sodium fluoride can be prepared from the reaction between sodium metal and fluorine gas.Which of the following properly represents the balanced chemical equation for this reaction?

Accepted Answer

The balanced chemical equation for the reaction between sodium metal and fluorine gas to produce sodium fluoride is:

2Na(s) + F2(g) → 2NaF(s)

Option E is the only one that correctly represents this balanced equation. Option A shows an incorrect formula for sodium fluoride, Option B only shows the formation of one molecule of sodium fluoride, Option C has 7 sodium atoms on the left side but only 1 on the right side, and Option D has an incorrect formula for sodium fluoride and an incorrect coefficient for fluorine gas.

Question 12

A sample of aluminum contains 2.91 × 10²² atoms of aluminum.What is the mass of this sample? [Molar mass: Al, 26.98 g/mol]

Accepted Answer

Number of moles of aluminum = (2.91 × 10^22 atoms) / (6.022 × 10^23 atoms/mol) = 0.0483 mol

Mass of aluminum = (0.0483 mol) x (26.98 g/mol) = 1.30 g.

Therefore, the answer is choice B, 1.30 g.

Question 13

What is the mass of one mole of diatomic hydrogen, H₂?

Accepted Answer

The molar mass of diatomic hydrogen (H2) is the sum of the atomic masses of two hydrogen atoms, which is 2.02 amu or grams per mole. Therefore, the correct answer is D) 2.02 g.

Question 14

The chemical equation below is unbalanced.What is the coefficient of water when the equation is balanced? Mg(OH)₂(s) + HCl(g) → MgCl₂(s) + H₂O(l)

Accepted Answer

In order to balance the equation, we need to have the same number of atoms of each element on both sides. There are 2 hydrogen atoms on the left side and 2 chlorine atoms on the right side, so we don't need to modify those. There is 1 magnesium atom and 1 sulfur atom on the left, and 1 magnesium atom and 1 sulfur atom on the right, so we don't need to modify those either. However, there are 1 oxygen atom and 1 hydrogen atom on the left (in the Mg(OH)2), while on the right there is only 1 oxygen atom and 0 hydrogen atoms (in the MgCl2). So we need to add water to balance the hydrogen and oxygen atoms. By adding 2 water molecules to the right side, we get:

Mg(OH)2(s) + 2HCl(g) → MgCl2(s) + 2H2O(l)

Now there are 4 hydrogen atoms and 4 oxygen atoms on both sides, so the equation is balanced. The coefficient of water is 2.

Question 15

Glucose (C₆H₁₂O₆) is an important energy-rich compound produced by photosynthesis according to the equation below.What mass of glucose can be produced from 2.61 mol of CO₂ and the necessary water? [Molar masses: C, 12.01 g/mol; H, 1.01 g/mol; O, 16.00 g/mol] 6CO₂(g) + 6H₂O(l) → C₆H₁₂O₆(l) + 6O₂(g)

Accepted Answer

First, we need to calculate the molar mass of glucose: (6 x molar mass of C) + (12 x molar mass of H) + (6 x molar mass of O) = (6 x 12.01 g/mol) + (12 x 1.01 g/mol) + (6 x 16.00 g/mol) = 180.18 g/mol Next, we use stoichiometry to find the mass of glucose produced from 2.61 mol of CO₂: 2.61 mol CO₂ x (1 mol glucose/6 mol CO₂) x (180.18 g/mol glucose) = 78.4 g glucose Therefore, the answer is (D) 78.4 g.

Question 16

Which has the greatest mass, one atom of carbon, one atom of hydrogen, or one atom of lithium?

Accepted Answer

The mass of an atom is primarily determined by the sum of the protons and neutrons in its nucleus. Carbon, with an atomic number of 6, has more protons (and typically more neutrons) than hydrogen (atomic number 1) and lithium (atomic number 3), making a carbon atom heavier than either a hydrogen or lithium atom.

Question 17

The mass of one atom of oxygen is 16.00 amu.What is the mass of one mole of elemental oxygen (O₂)?

Accepted Answer

One mole of any element has a mass equal to its atomic mass in grams. Therefore, one mole of oxygen has a mass of 16.00 g.

Question 18

Which of the following statements concerning a voltaic cell is FALSE?

Accepted Answer

The oxidation half reaction occurs at the anode, not the cathode. The cathode is where reduction occurs.

Question 19

Upon mixing a clear colorless BaCl₂ solution with a clear, colorless Na₂SO₄ solution according to the reaction below, a student observes a white cloudiness form.What is responsible for the cloudiness that is observed? BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq)

Accepted Answer

The formation of a white solid (BaSO4) indicates that a precipitation reaction has occurred. Precipitation reactions occur when two aqueous solutions react to form an insoluble solid. In this case, the Ba2+ and SO42- ions from the BaCl2 and Na2SO4 solutions react to form BaSO4, which is insoluble in water and forms a white solid. Therefore, the responsible compound for the cloudiness observed is BaSO4, which is formed as a result of the reaction between BaCl2 and Na2SO4.

Question 20

What is the general term for the process in which a chemical species loses electrons?

Accepted Answer

Oxidation is the general term for the process in which a chemical species loses electrons.

Quiz 4: Calculations, Chemical Changes, and the Chemical Equation

Which statement best describes the Law of Conservation of Mass?

The unbalanced equation for the combustion of octane, a component of gasoline, is shown below.What would be the coefficient of carbon dioxide once the equation is balanced? C₈H₁₈(l) + O₂(g) → CO₂(g) + H₂O(l)

Which notation properly indicates how two molecules of diatomic oxygen would be represented in a chemical equation?

The chemical equation below is not balanced.Balance the equation, then determine which statement concerning the balanced equation is TRUE. KClO₃(s) → KCl(s) + O₂(g)

Hydrogen fluoride will react with glass (silicon dioxide, SiO₂) according to the equation below.What mass of HF is required to react completely with 16.0 g of glass?[Molar masses: Si, 28.09 g/mol; F, 19.00 g/mol; H, 1.01 g/mol; O, 16.00 g/mol] 4HF(g) + SiO₂(s) → SiF₄(g) + 2H₂O(g)

How many molecules of water are present in a 5.65 mole sample of water?

Consider the chemical equation shown below.How many moles of oxygen gas are needed to react with hydrogen to form one mole of water? 2H₂(g) + O₂(g) → 2H₂O(l)

What is the mass of 4.00 moles of helium, the gas commonly used to fill party balloons and lighter-than-air ships?

Aluminum metal and oxygen gas are produced when aluminum oxide is heated at high temperature.Which statement concerning this chemical change is true?

Which symbol, often found in chemical equations, indicates that a substance is dissolved in water?

The fluoride rinse in dental offices usually contains sodium fluoride.Sodium fluoride can be prepared from the reaction between sodium metal and fluorine gas.Which of the following properly represents the balanced chemical equation for this reaction?

A sample of aluminum contains 2.91 × 10²² atoms of aluminum.What is the mass of this sample? [Molar mass: Al, 26.98 g/mol]

What is the mass of one mole of diatomic hydrogen, H₂?

The chemical equation below is unbalanced.What is the coefficient of water when the equation is balanced? Mg(OH) ₂(s) + HCl(g) → MgCl₂(s) + H₂O(l)

Which has the greatest mass, one atom of carbon, one atom of hydrogen, or one atom of lithium?

The mass of one atom of oxygen is 16.00 amu.What is the mass of one mole of elemental oxygen (O₂) ?

Which of the following statements concerning a voltaic cell is FALSE?

Upon mixing a clear colorless BaCl₂ solution with a clear, colorless Na₂SO₄ solution according to the reaction below, a student observes a white cloudiness form.What is responsible for the cloudiness that is observed? BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq)

What is the general term for the process in which a chemical species loses electrons?

Quiz 4: Calculations, Chemical Changes, and the Chemical Equation

Which statement best describes the Law of Conservation of Mass?

The unbalanced equation for the combustion of octane, a component of gasoline, is shown below.What would be the coefficient of carbon dioxide once the equation is balanced? C8H18(l) + O2(g) → CO2(g) + H2O(l)

Which notation properly indicates how two molecules of diatomic oxygen would be represented in a chemical equation?

The chemical equation below is not balanced.Balance the equation, then determine which statement concerning the balanced equation is TRUE. KClO3(s) → KCl(s) + O2(g)

Hydrogen fluoride will react with glass (silicon dioxide, SiO2) according to the equation below.What mass of HF is required to react completely with 16.0 g of glass?[Molar masses: Si, 28.09 g/mol; F, 19.00 g/mol; H, 1.01 g/mol; O, 16.00 g/mol] 4HF(g) + SiO2(s) → SiF4(g) + 2H2O(g)

How many molecules of water are present in a 5.65 mole sample of water?

Consider the chemical equation shown below.How many moles of oxygen gas are needed to react with hydrogen to form one mole of water? 2H2(g) + O2(g) → 2H2O(l)

What is the mass of 4.00 moles of helium, the gas commonly used to fill party balloons and lighter-than-air ships?

Aluminum metal and oxygen gas are produced when aluminum oxide is heated at high temperature.Which statement concerning this chemical change is true?

Which symbol, often found in chemical equations, indicates that a substance is dissolved in water?

The fluoride rinse in dental offices usually contains sodium fluoride.Sodium fluoride can be prepared from the reaction between sodium metal and fluorine gas.Which of the following properly represents the balanced chemical equation for this reaction?

A sample of aluminum contains 2.91 × 1022 atoms of aluminum.What is the mass of this sample? [Molar mass: Al, 26.98 g/mol]

What is the mass of one mole of diatomic hydrogen, H2?

The chemical equation below is unbalanced.What is the coefficient of water when the equation is balanced? Mg(OH) 2(s) + HCl(g) → MgCl2(s) + H2O(l)

Which has the greatest mass, one atom of carbon, one atom of hydrogen, or one atom of lithium?

The mass of one atom of oxygen is 16.00 amu.What is the mass of one mole of elemental oxygen (O2) ?

Which of the following statements concerning a voltaic cell is FALSE?

Upon mixing a clear colorless BaCl2 solution with a clear, colorless Na2SO4 solution according to the reaction below, a student observes a white cloudiness form.What is responsible for the cloudiness that is observed? BaCl2(aq) + Na2SO4(aq) → BaSO4(s) + 2NaCl(aq)

What is the general term for the process in which a chemical species loses electrons?

The unbalanced equation for the combustion of octane, a component of gasoline, is shown below.What would be the coefficient of carbon dioxide once the equation is balanced? C₈H₁₈(l) + O₂(g) → CO₂(g) + H₂O(l)

The chemical equation below is not balanced.Balance the equation, then determine which statement concerning the balanced equation is TRUE. KClO₃(s) → KCl(s) + O₂(g)

Hydrogen fluoride will react with glass (silicon dioxide, SiO₂) according to the equation below.What mass of HF is required to react completely with 16.0 g of glass?[Molar masses: Si, 28.09 g/mol; F, 19.00 g/mol; H, 1.01 g/mol; O, 16.00 g/mol] 4HF(g) + SiO₂(s) → SiF₄(g) + 2H₂O(g)

Consider the chemical equation shown below.How many moles of oxygen gas are needed to react with hydrogen to form one mole of water? 2H₂(g) + O₂(g) → 2H₂O(l)

A sample of aluminum contains 2.91 × 10²² atoms of aluminum.What is the mass of this sample? [Molar mass: Al, 26.98 g/mol]

What is the mass of one mole of diatomic hydrogen, H₂?

The chemical equation below is unbalanced.What is the coefficient of water when the equation is balanced? Mg(OH) ₂(s) + HCl(g) → MgCl₂(s) + H₂O(l)

The mass of one atom of oxygen is 16.00 amu.What is the mass of one mole of elemental oxygen (O₂) ?

Upon mixing a clear colorless BaCl₂ solution with a clear, colorless Na₂SO₄ solution according to the reaction below, a student observes a white cloudiness form.What is responsible for the cloudiness that is observed? BaCl₂(aq) + Na₂SO₄(aq) → BaSO₄(s) + 2NaCl(aq)