Stoichiometry: Balancing Equations and Chemical Calculations

Question 1

The mole concept refers to:

Accepted Answer

A unit that measures the quantity of a substance

Answer

The mass-to-molecular weight ratio of a substance

Answer

A measure of the number of molecules in a substance

Answer

The mass-to-volume ratio of a substance

Question 2

Which of the following is a strong acid?

Accepted Answer

Hydrochloric acid

Answer

Acetic acid

Answer

Carbonic acid

Answer

Ammonia

Question 3

What is the pH of a 0.1 M solution of NaOH?

Accepted Answer

13

Answer

1

Answer

7

Answer

14

Question 4

Identify which reaction is a redox reaction:

Accepted Answer

Combustion of methane

Answer

Neutralization of an acid and a base

Answer

Dissolving of salt in water

Answer

Precipitation of a metal hydroxide

Question 5

What characterizes the concept of a mole?

Accepted Answer

It relates the mass of a substance to the number of atoms or molecules it contains.

Answer

It allows us to convert between mass and volume of a substance.

Answer

It is used to determine the empirical formula of a compound.

Answer

It can be used to predict the products of a chemical reaction.

Question 6

What is the definition of molar mass?

Accepted Answer

The mass of one mole of a substance.

Answer

The number of moles in one gram of a substance.

Answer

The mass of one atom of a substance.

Question 7

Which of the following is not a type of stoichiometric calculation?

Accepted Answer

Volume-to-volume calculations

Answer

Mass-to-mass calculations

Answer

Mass-to-mole calculations

Answer

Mole-to-mass calculations

Question 8

Calculate the theoretical yield (in grams) of sodium sulfate (Na2SO4) when 10.0 g of sodium hydroxide (NaOH) reacts completely with excess sulfuric acid (H2SO4).

Accepted Answer

11.7 g

Answer

5.85 g

Answer

6.25 g

Answer

9.76 g

Question 9

If the actual yield of a reaction is 8.50 g and the theoretical yield is 10.00 g, calculate the percent yield.

Accepted Answer

85.0%

Answer

93.8%

Answer

106.2%

Answer

117.6%

Question 10

When a non-volatile solute is dissolved in a solvent, what happens to the boiling point of the solvent?

Accepted Answer

It increases.

Answer

It decreases.

Answer

It stays the same.

Answer

It cannot be determined without more information.

Question 11

Balance the following chemical equation: H2 + O2 → H2O

Accepted Answer

2H2 + O2 → 2H2O

Answer

2H + O → H2O

Answer

2H2O → 2H + O2

Answer

O2 + 4H → 2H2O

Question 12

In the reaction: 2C8H18 + 25O2 → 16CO2 + 18H2O, which reactant is the limiting reactant?

Accepted Answer

C8H18

Answer

O2

Answer

CO2

Answer

H2O

Question 13

Which of the following is a strong acid?

Accepted Answer

Hydrochloric acid (HCl)

Answer

Acetic acid (CH3COOH)

Answer

Ammonia (NH3)

Answer

Sodium hydroxide (NaOH)

Question 14

What is the pH of a solution with a hydrogen ion concentration of 1 x 10^-4 M?

Accepted Answer

4

Answer

7

Answer

10

Answer

14

Question 15

Which of the following is a redox reaction?

Accepted Answer

Rusting of iron

Answer

Neutralization of an acid and a base

Answer

Precipitation of a metal hydroxide

Answer

Dissolution of salt in water

Question 16

A balanced chemical equation demonstrates that:

Accepted Answer

The number of atoms of each element is identical on both sides of the equation.

Answer

The total mass of the reactants is equal to the total mass of the products.

Answer

The number of molecules of each compound is the same on both sides.

Answer

The moles of each reactant are equivalent to the moles of each product.

Question 17

Define the mole.

Accepted Answer

The quantity of an element in grams that contains Avogadro's number of atoms.

Answer

The number of atoms in 12 grams of carbon.

Answer

The amount of a substance containing 1 gram of hydrogen.

Answer

The volume of a gas at STP that comprises 1 mole of atoms.

Question 18

Which reaction below is a redox reaction?

Accepted Answer

CH4 + 2O2 → CO2 + 2H2O

Answer

NaOH + HCl → NaCl + H2O

Answer

2Na + Cl2 → 2NaCl

Answer

AgNO3 + NaCl → AgCl + NaNO3

Question 19

Identify the strong acid:

Accepted Answer

Hydrochloric acid (HCl)

Answer

Acetic acid (CH3COOH)

Answer

Carbonic acid (H2CO3)

Answer

Ammonia (NH3)

Question 20

An exothermic reaction is at equilibrium. What change would shift the equilibrium towards the reactants?

Accepted Answer

Decreasing the temperature

Answer

Increasing the temperature

Answer

Adding more reactants

Answer

Adding more products

Question 21

How does the mole concept enable us to determine the quantitative relationships between reactants and products in chemical reactions?

Accepted Answer

It allows us to relate the mass of a substance to the number of its constituent particles.

Answer

It doesn't play a role in stoichiometry.

Answer

It helps balance chemical equations.

Question 22

The mole is defined as the amount of substance that contains how many elementary entities?

Accepted Answer

6.022 x 10^23

Answer

1 gram of its atomic mass

Answer

22.4 liters at STP

Answer

The ratio of the mass of a compound to the mass of one of its elements

Question 23

In the reaction: 2Al + 3Cl2 → 2AlCl3, which reactant will be entirely consumed first, limiting the amount of product that can be formed?

Accepted Answer

Aluminum (Al)

Answer

Chlorine (Cl2)

Answer

Aluminum chloride (AlCl3)

Answer

The reaction has no limiting reactant

Question 24

What is the oxidation number of sulfur in the compound H2SO4?

Accepted Answer

+6

Answer

-2

Answer

+2

Answer

+4

Question 25

Which of the following is considered a strong acid?

Accepted Answer

Hydrochloric acid (HCl)

Answer

Acetic acid (CH3COOH)

Answer

Phosphoric acid (H3PO4)

Answer

Carbonic acid (H2CO3)

Question 26

Which of the following is a buffer solution?

Accepted Answer

0.1 M CH3COOH + 0.1 M CH3COONa

Answer

Pure water

Answer

0.1 M HCl

Answer

0.1 M NaOH

Question 27

What is the mole concept?

Accepted Answer

A concept that relates the number of particles of a substance to its mass

Answer

A concept that expresses the amount of a substance present in a specific mass

Answer

A concept that describes the ratio of reactants to products in a chemical reaction

Answer

A concept used to measure the concentration of a solution

Question 28

What is the molar mass of sodium chloride (NaCl)?

Accepted Answer

58.5 g/mol

Answer

23 g/mol

Answer

35.5 g/mol

Answer

71 g/mol

Question 29

Which of the following is a buffer solution?

Accepted Answer

A solution containing a weak acid and its conjugate base

Answer

A solution containing a strong acid and its conjugate base

Answer

A solution containing a weak base and its conjugate acid

Answer

A solution containing a strong base and its conjugate acid

Question 30

Which of the following is NOT a fundamental unit in the International System of Units (SI)?

Accepted Answer

Pound (lb)

Answer

Mole (mol)

Answer

Gram (g)

Answer

Liter (L)

Question 31

The mole concept states that:

Accepted Answer

A mole represents a specific number of particles (atoms, molecules, or ions) of a substance.

Answer

A mole represents a specific mass of a substance.

Answer

A mole represents the molar mass of a substance.

Answer

A mole represents the density of a substance.

Question 32

What is the balanced chemical equation for the combustion of methane (CH₄)?

Accepted Answer

CH₄ + 2O₂ → CO₂ + 2H₂O

Answer

CH₄ + O₂ → CO + 2H₂O

Answer

CH₄ + 2O₂ → CO + H₂O

Answer

CH₄ + O₂ → C + 2H₂O

Question 33

Which of the following factors does NOT affect the rate of a chemical reaction?

Accepted Answer

Magnetic field strength

Answer

Temperature

Answer

Concentration of reactants

Answer

Surface area of reactants

Question 34

What is the equilibrium constant expression for the reaction A + 2B ⇌ C?

Accepted Answer

K = [A][B]^2/[C]

Answer

K = [C]

Answer

K = [C]/[A][B]^2

Answer

K = [A][B]/[C]

Question 35

Which of the following is a strong acid?

Accepted Answer

Hydrochloric acid (HCl)

Answer

Acetic acid (CH₃COOH)

Answer

Carbonic acid (H₂CO₃)

Answer

Ammonia (NH₃)

Question 36

In the balanced chemical equation 2 Na + Cl₂ → 2 NaCl, what is the mole ratio of sodium (Na) to chlorine (Cl)?

Accepted Answer

2:1

Answer

1:2

Answer

1:1

Answer

4:1

Question 37

If 5.00 grams of magnesium (Mg) reacts completely with excess oxygen gas (O₂) to form magnesium oxide (MgO), what is the theoretical yield of MgO? (Molar mass of Mg = 24.31 g/mol, MgO = 40.30 g/mol)

Accepted Answer

8.28 g

Answer

10.0 g

Answer

5.00 g

Answer

2.00 g

Question 38

A reaction has a theoretical yield of 15.0 g. If the actual yield is 12.5 g, what is the percent yield?

Accepted Answer

83.3%

Answer

120%

Answer

1.2%

Answer

16.7%

Question 39

Which of these is NOT a typical step involved in performing stoichiometric calculations?

Accepted Answer

Converting grams to milliliters

Answer

Converting grams to moles

Answer

Using mole ratios from the balanced equation

Answer

Balancing the chemical equation

Question 40

A chemist conducts a reaction and obtains an actual yield of 10.0 g. If the theoretical yield is 12.5 g, what is the percent yield?

Accepted Answer

80.0%

Answer

125%

Answer

20.0%

Answer

1.25%

Question 41

What is the balanced chemical equation for the reaction between calcium (Ca) and oxygen (O₂) to form calcium oxide (CaO)?

Accepted Answer

2 Ca + O₂ → 2 CaO

Answer

Ca + O₂ → CaO

Answer

Ca + O → CaO

Answer

Ca₂ + O₂ → 2 CaO

Question 42

Which of these is NOT a valid unit for expressing the amount of a substance?

Accepted Answer

Liters

Answer

Grams

Answer

Molecules

Answer

Moles

Question 43

What is the balanced chemical equation for the reaction of sodium (Na) with chlorine gas (Cl₂) to produce sodium chloride (NaCl)?

Accepted Answer

2 Na + Cl₂ → 2 NaCl

Answer

Na + Cl → NaCl

Answer

Na + Cl₂ → NaCl

Answer

Na₂ + Cl₂ → 2 NaCl

Question 44

Complete combustion of 2 moles of propane (C₃H₈) produces how many moles of carbon dioxide (CO₂)?

Accepted Answer

8 moles

Answer

2 moles

Answer

6 moles

Answer

4 moles

Question 45

Which of these is NOT typically required to solve stoichiometric problems?

Accepted Answer

Determining the volume of the reactants and products

Answer

Converting grams to moles

Answer

Balancing the chemical equation

Question 46

What is the limiting reactant in a reaction where 2 moles of sodium (Na) react with 1 mole of chlorine gas (Cl₂)?

Accepted Answer

Chlorine gas (Cl₂)

Answer

Sodium chloride (NaCl)

Answer

Sodium (Na)

Question 47

What is the theoretical yield of a reaction if 5.0 g of reactant A produces 8.0 g of product B?

Accepted Answer

8.0 g

Answer

5.0 g

Answer

13.0 g

Question 48

What is the percent yield of a reaction if the actual yield is 10 g and the theoretical yield is 12 g?

Accepted Answer

83.3%

Answer

90%

Answer

120%

Answer

100%

Question 49

Which of the following is a common application of stoichiometry in the real world?

Accepted Answer

Determining the amount of reactants needed for a chemical process in industry

Answer

Designing a new video game

Answer

Predicting the weather

Question 50

The mole concept is important in stoichiometry because it allows us to:

Accepted Answer

Relate the mass of reactants and products to the number of molecules involved in a reaction

Answer

Determine the volume of gases involved in a reaction

Answer

Predict the rate of a chemical reaction