Stoichiometry: Master Chemical Calculations for Biology Majors

Question 1

Which of the following topics is not directly related to stoichiometry?

Accepted Answer

Quantum chemistry

Answer

Percent composition

Answer

Reaction stoichiometry

Answer

Solutions and their properties

Question 2

To determine the mass of a substance, given its number of moles and molar mass, which formula should you use?

Accepted Answer

Mass = moles × molar mass (g)

Answer

Mass = moles ÷ molar mass (g)

Answer

Mass = molar mass ÷ moles (g)

Answer

Mass = molar mass - moles (g)

Question 3

Which of the following is the SI unit of amount of substance?

Accepted Answer

Mole

Answer

Gram

Answer

Liter

Answer

Kilogram

Question 4

What is the numerical value of Avogadro's number?

Accepted Answer

6.022 x 10^23

Answer

6.022 x 10^20

Answer

6.022 x 10^24

Answer

6.022 x 10^25

Question 5

Calculate the molar mass of sodium chloride (NaCl).

Accepted Answer

58.5 g/mol

Answer

23 g/mol

Answer

74.6 g/mol

Answer

82.3 g/mol

Question 6

Which of the following is NOT a unit of volume?

Accepted Answer

Mole

Answer

Liter

Answer

Milliliter

Answer

Cubic centimeter

Question 7

What volume does 0.5 moles of an ideal gas occupy at standard temperature and pressure (STP)?

Accepted Answer

22.4 liters

Answer

11.2 liters

Answer

33.6 liters

Answer

44.8 liters

Question 8

Identify the balanced chemical equation:

Accepted Answer

2 H2 + O2 → H2O

Answer

2 H2 + O → H2O

Answer

2 H + O2 → H2O

Answer

H2 + O → 2 H2O

Question 9

Which of the following is the numerical value of Avogadro's number?

Accepted Answer

6.023 x 10^23

Answer

1.008 x 10^23

Answer

3.01 x 10^23

Answer

1.66 x 10^-24

Question 10

Identify the balanced chemical equation from the given options:

Accepted Answer

2H2 + O2 -> 2H2O

Answer

H2 + O -> H2O

Answer

H2 + 2O -> H2O2

Answer

H2O -> H2 + O2

Question 11

Which of the following is not a unit for expressing concentration?

Accepted Answer

Percentage by mass

Answer

Molarity (M)

Answer

Molality (m)

Answer

Parts per million (ppm)

Question 12

Which of the following is NOT a unit of volume?

Accepted Answer

Mole

Answer

Liter

Answer

Milliliter

Answer

Cubic centimeter

Question 13

Which of the following compounds has the highest formula mass?

Accepted Answer

C6H12O6

Answer

H2O

Answer

CO2

Answer

NaCl

Question 14

How does stoichiometry contribute to the quality, safety, and effectiveness of pharmaceuticals in their development and production?

Accepted Answer

Stoichiometry ensures precise ingredient ratios, optimizing drug efficacy and safety.

Answer

Stoichiometry is irrelevant to drug quality, focusing solely on reactant quantities.

Answer

Stoichiometry is limited to known reactions and has no role in new drug development.

Answer

Stoichiometry only considers mass relationships, ignoring other factors affecting product safety.

Question 15

How does stoichiometry contribute to predicting equilibrium concentrations in chemical reactions?

Accepted Answer

Stoichiometry provides the mole ratios between reactants and products, which, along with equilibrium constants, facilitate the calculation of equilibrium concentrations.

Answer

Stoichiometry alone is sufficient to determine equilibrium concentrations, without the need for additional information.

Question 16

Calculate the molar mass of sodium chloride (NaCl).

Accepted Answer

58.44 g/mol

Answer

35.45 g/mol

Answer

22.99 g/mol

Answer

116.88 g/mol

Question 17

What is the limiting reactant in the following reaction: 2Al + 3Cl2 → 2AlCl3?

Accepted Answer

Aluminum (Al)

Answer

Chlorine (Cl)

Answer

Aluminum chloride (AlCl3)

Question 18

Which of the following describes a buffer solution?

Accepted Answer

A solution that resists changes in pH upon the addition of small amounts of acid or base.

Answer

A solution with a pH of exactly 7.0

Answer

A solution with a high concentration of hydrogen ions

Question 19

What is the activation energy for a reaction?

Accepted Answer

The minimum energy that colliding molecules must possess to react.

Answer

The energy released during a reaction.

Answer

The energy required to break bonds in reactants

Question 20

Precisely define the mole concept.

Accepted Answer

The amount of substance that contains as many elementary entities as there are atoms in 0.012 kilograms of carbon-12.

Answer

The mass of a substance that contains 6.022 × 10^23 atoms.

Question 21

Define Avogadro's number

Accepted Answer

6.022 × 10^23

Answer

2.731 × 10^22

Answer

1.661 × 10^-24

Answer

0.012

Question 22

In a chemical reaction involving 2.00 moles of methane (CH4) and 4.00 moles of oxygen (O2), identify the limiting reactant.

Accepted Answer

Methane (CH4)

Answer

Oxygen (O2)

Answer

Carbon dioxide (CO2)

Answer

Water (H2O)

Question 23

Define the equilibrium constant (Kc) based on the given equilibrium expression: [A]^2[B]/[C]

Accepted Answer

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

Answer

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

Answer

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

Question 24

Which of the following is the International System of Units (SI) unit of amount of substance?

Accepted Answer

mole

Answer

liter

Answer

joule

Answer

gram

Question 25

Which of the following represents the limiting reactant in the reaction between 2.00 moles of propane (C3H8) and 7.00 moles of oxygen (O2)?

Accepted Answer

Propane (C3H8)

Answer

Neither is a limiting reactant

Answer

Both are limiting reactants

Answer

Oxygen (O2)

Question 26

What is the percent yield of a reaction if the theoretical yield is 25.0 g and the actual yield is 18.5 g?

Accepted Answer

74.0%

Answer

150.0%

Answer

126.0%

Answer

42.5%

Question 27

How many grams of sodium hydroxide (NaOH) are needed to react completely with 10.0 g of hydrochloric acid (HCl)? (Molar masses: NaOH = 40.00 g/mol, HCl = 36.46 g/mol)

Balanced Equation: NaOH + HCl → NaCl + H2O

Accepted Answer

10.9 g

Answer

58.44 g

Answer

40.0 g

Answer

1.09 g

Question 28

What is the limiting reactant in a reaction where 20.0 g of sodium (Na) reacts with 15.0 g of chlorine gas (Cl2) to form sodium chloride (NaCl)? (Molar masses: Na = 22.99 g/mol, Cl2 = 70.90 g/mol)

Balanced Equation: 2Na + Cl2 → 2NaCl

Accepted Answer

Sodium (Na)

Answer

There is no limiting reactant

Answer

Sodium chloride (NaCl)

Answer

Chlorine gas (Cl2)

Question 29

A reaction has a theoretical yield of 20.0 g of product, and 16.0 g of product is actually obtained. What is the percent yield of this reaction?

Accepted Answer

80.0%

Answer

125%

Answer

16.0%

Answer

20.0%

Question 30

In a chemical reaction, the coefficients in the balanced equation represent the ______ of reactants and products involved.

Accepted Answer

mole ratios

Answer

volume ratios

Answer

density ratios

Answer

mass ratios

Question 31

What is Avogadro's number?

Accepted Answer

6.022 x 10^23

Answer

3.15 x 10^7

Answer

9.109 x 10^-31

Answer

1.66 x 10^-24

Question 32

What is the molar mass of calcium carbonate?

Accepted Answer

100.09 g/mol

Answer

22.99 g/mol

Answer

70.90 g/mol

Answer

35.45 g/mol

Question 33

Which of the following reactions is balanced?

Accepted Answer

CH4 + 2O2 → CO2 + 2H2O

Answer

CH4 + O2 → CO + 2H2

Answer

2CH4 + O2 → CO2 + 2H2O

Question 34

What is the percent yield of a reaction that produces 10 grams of product if the theoretical yield is 15 grams?

Accepted Answer

66.67%

Answer

150%

Answer

100%

Answer

33.33%

Question 35

What is the molar mass of glucose (C₆H₁₂O₆)?

Accepted Answer

180.16 g/mol

Answer

204.22 g/mol

Answer

120.11 g/mol

Answer

150.13 g/mol

Question 36

How many moles of sodium chloride (NaCl) are present in 58.44 g of NaCl?

Accepted Answer

1 mole

Answer

10 moles

Answer

0.5 moles

Answer

2 moles

Question 37

What volume (in L) does 2.5 moles of nitrogen gas (N₂) occupy at standard temperature and pressure (STP)?

Accepted Answer

56 L

Answer

11.2 L

Answer

22.4 L

Answer

100 L

Question 38

How many grams of magnesium oxide (MgO) are produced when 4.8 g of magnesium (Mg) reacts completely with oxygen?

Accepted Answer

8.0 g

Answer

4.0 g

Answer

16.0 g

Answer

12.0 g

Question 39

What is the limiting reactant in the following reaction if 10 g of sodium (Na) reacts with 10 g of chlorine gas (Cl₂)? 2Na + Cl₂ → 2NaCl

Accepted Answer

Chlorine gas (Cl₂)

Answer

Sodium (Na)

Answer

Neither reactant is limiting

Answer

Both reactants are limiting

Question 40

What is the theoretical yield of water (H₂O) in grams when 5.0 g of hydrogen gas (H₂) reacts completely with excess oxygen?

Accepted Answer

45 g

Answer

90 g

Answer

22.5 g

Question 41

If 10 g of a compound is experimentally found to produce 8.0 g of a product, what is the percent yield of the reaction?

Accepted Answer

80%

Answer

20%

Answer

125%

Answer

100%

Question 42

Which of the following is NOT a direct application of stoichiometry in biology?

Accepted Answer

Predicting the color of a flower

Answer

Calculating the amount of ATP produced in cellular respiration

Answer

Estimating the amount of protein synthesized by a cell

Answer

Determining the amount of glucose needed for photosynthesis

Question 43

How many atoms are present in 2.0 moles of carbon dioxide (CO₂)?

Accepted Answer

3.6 x 10²⁴ atoms

Answer

1.8 x 10²⁴ atoms

Answer

1.2 x 10²⁴ atoms

Answer

6.02 x 10²³ atoms

Question 44

Which of the following is NOT a valid unit for molar mass?

Accepted Answer

g/L

Answer

g/mol

Answer

kg/mol

Answer

amu

Question 45

What is the mass of 2.5 moles of sodium chloride (NaCl)? (Molar mass of NaCl = 58.44 g/mol)

Accepted Answer

146.1 g

Answer

29.22 g

Answer

233.76 g

Answer

58.44 g

Question 46

How many moles of carbon dioxide (CO2) are produced when 0.5 moles of propane (C3H8) are completely burned in excess oxygen? (Balanced equation: C3H8 + 5O2 -> 3CO2 + 4H2O)

Accepted Answer

1.5 moles

Answer

4.0 moles

Answer

0.5 moles

Answer

3.0 moles

Question 47

What volume (in liters) does 10 grams of nitrogen gas (N2) occupy at standard temperature and pressure (STP)? (Molar mass of N2 = 28.02 g/mol, molar volume at STP = 22.4 L/mol)

Accepted Answer

8.0 L

Answer

1.0 L

Answer

22.4 L

Answer

10.0 L

Question 48

Which of the following is NOT a direct application of stoichiometry in biological research?

Accepted Answer

Determining the optimal temperature for enzyme activity

Answer

Analyzing the concentration of a particular protein in a sample

Answer

Calculating the amount of DNA required for a specific experiment

Question 49

What is the limiting reactant in the following reaction if 20 grams of sodium (Na) reacts with 30 grams of chlorine gas (Cl2)? (Molar mass of Na = 22.99 g/mol, Molar mass of Cl2 = 70.90 g/mol)

Accepted Answer

Sodium (Na)

Answer

Chlorine gas (Cl2)

Answer

Both are limiting reactants

Answer

Neither is a limiting reactant

Question 50

What is the percentage yield of a reaction if 15 grams of product are actually obtained when the theoretical yield is 20 grams?

Accepted Answer

75%

Answer

25%

Answer

66.7%

Answer

133.3%

Question 51

Which of the following statements is true about Avogadro's number?

Accepted Answer

It represents the number of particles in one mole of any substance.

Answer

It is the mass of one mole of any substance.

Answer

It is the volume of one mole of any substance at STP.

Question 52

What is the mole ratio between carbon dioxide (CO2) and water (H2O) in the following balanced equation: CH4 + 2O2 -> CO2 + 2H2O?

Accepted Answer

1:2

Answer

4:1

Answer

1:1

Answer

2:1

Question 53

How many grams of magnesium oxide (MgO) are produced when 4.86 grams of magnesium (Mg) reacts completely with oxygen? (Molar mass of Mg = 24.31 g/mol, Molar mass of MgO = 40.30 g/mol)

Accepted Answer

8.06 g

Answer

4.86 g

Answer

24.31 g

Question 54

Which of the following is a valid unit for expressing molar concentration?

Accepted Answer

mol/L

Answer

L/mol

Answer

g/mL

Answer

g/mol