Question 1

Which of the following best describes the purpose of stoichiometry in chemical reactions?

Accepted Answer

To calculate the quantitative relationships between reactants and products using a balanced chemical equation.

Question 2

Given the balanced equation $$2 \mathrm{H}_2 (g) + \mathrm{O}_2 (g) \rightarrow 2 \mathrm{H}_2\mathrm{O} (g)$$, how many moles of $$\mathrm{O}_2$$ are required to produce 4 moles of $$\mathrm{H}_2\mathrm{O}$$?

Accepted Answer

2 moles

Question 3

In the reaction $$4 \mathrm{Cr} (s) + 3 \mathrm{O}_2 (g) \rightarrow 2 \mathrm{Cr}_2\mathrm{O}_3 (s)$$, how many moles of $$\mathrm{Cr}_2\mathrm{O}_3$$ are produced when 34.69 g of Cr reacts with excess oxygen? (Molar mass of Cr = 52.00 g/mol)

Accepted Answer

0.667 moles

Question 4

Which step in stoichiometric calculations involves converting the given quantity into moles?

Accepted Answer

Step 2

Question 5

For the reaction $$8 \mathrm{KClO}_3 + \mathrm{C}_{12}\mathrm{H}_{22}\mathrm{O}_{11} ightarrow 8 \mathrm{KCl} + 12 \mathrm{CO}_2 + 11 \mathrm{H}_2\mathrm{O}$$, if $$2.33 	imes 10^4$ formula units of potassium chlorate are reacted, how many grams of carbon dioxide will be produced? (Molar mass of $$\mathrm{CO}_2 = 44.01$$ g/mol, Avogadro's number = 6.022$$ 	imes $$10^{23})$$

Accepted Answer

2.04 	imes $$10^{-18}$ g

Question 6

In the reaction $$\mathrm{CH}_3\mathrm{CH}_2\mathrm{OH} (l) + 3 \mathrm{O}_2 (g) \rightarrow 3 \mathrm{H}_2\mathrm{O} (l) + 2 \mathrm{CO}_2 (g)$$, how many milliliters of ethanol (density = 0.789 g/mL, molar mass = 46.07 g/mol) are needed to produce 4.8 g of $$\mathrm{H}_2\mathrm{O}$$?

Accepted Answer

4.39 mL

Question 7

What is the correct mole ratio of $$\mathrm{H}_2 to$$ $$\mathrm{H}_2\mathrm{O} in $$the reaction $$2 \mathrm{H}_2 (g) + \mathrm{O}_2 (g) \rightarrow 2 \mathrm{H}_2\mathrm{O} (g)$$?

Accepted Answer

2:2

Question 8

If 12.3 g of $$\mathrm{H}_2$$ reacts with excess $$\mathrm{O}_2$$, how many grams of $$\mathrm{H}_2\mathrm{O}$$ are produced? (Molar mass of $$\mathrm{H}_2 = 2.02 g/$$mol, $$\mathrm{H}_2\mathrm{O} = 18.02 g/$$mol)

Accepted Answer

109.7 g

Question 9

Which of the following is NOT a necessary step in solving a stoichiometry problem?

Accepted Answer

Determining the color of the reactants

Question 10

A student is given 30.0 g of $$\mathrm{O}_2 to $$react with $$\mathrm{H}_2$$ according to $$2 \mathrm{H}_2 (g) + \mathrm{O}_2 (g) \rightarrow 2 \mathrm{H}_2\mathrm{O} (g). $$How many grams of $$\mathrm{H}_2\mathrm{O}$$ can be produced? (Molar mass of $$\mathrm{O}_2 = 32.00 g/$$mol, $$\mathrm{H}_2\mathrm{O} = 18.02 g/$$mol)

Accepted Answer

33.8 g

Question 11

In a chemical reaction, what does the coefficient in a balanced equation represent?

Accepted Answer

The number of moles of each substance involved

Question 12

Which of the following conversions is necessary when the given quantity is in grams and the unknown is in molecules?

Accepted Answer

Grams to moles, moles to molecules

Question 13

If a compound is in excess during a reaction, what should you do in stoichiometric calculations?

Accepted Answer

Ignore the excess compound and use the limiting reactant for calculations

Question 14

In the reaction $$2 \mathrm{H}_2 (g) + \mathrm{O}_2 (g) \rightarrow 2 \mathrm{H}_2\mathrm{O} (g)$$, what is the limiting reactant if you have 10.0 g of $$\mathrm{H}_2$$ and 10.0 g of $$\mathrm{O}_2$$? (Molar masses: $$\mathrm{H}_2 = 2.02 g/$$mol, $$\mathrm{O}_2 = 32.00 g/$$mol)

Accepted Answer

$$\mathrm{O}_2$$

Question 15

Which real-world scenario best illustrates the use of stoichiometry?

Accepted Answer

Calculating the amount of medication needed for a chemical reaction in the body

Question 16

A chemist needs to produce 200.0 g of $$\mathrm{H}_2\mathrm{O}$$ using $$\mathrm{H}_2$$ and $$\mathrm{O}_2. $$How many grams of $$\mathrm{H}_2$$ are required? (Molar mass: $$\mathrm{H}_2 = 2.02 g/$$mol, $$\mathrm{H}_2\mathrm{O} = 18.02 g/$$mol)

Accepted Answer

22.4 g

Question 17

Which of the following is the correct sequence of steps for solving a stoichiometry problem?

Accepted Answer

Map the problem, convert to moles, mole-to-mole comparison, convert to final units

Question 18

If you start with 8.00 g of $$\mathrm{KClO}_3 ($$molar mass = 122.55 g/mol), how many moles of $$\mathrm{KClO}_3 do $$you have?

Accepted Answer

0.0653 moles

Question 19

In the reaction $$\mathrm{CH}_3\mathrm{CH}_2\mathrm{OH} (l) + 3 \mathrm{O}_2 (g) \rightarrow 3 \mathrm{H}_2\mathrm{O} (l) + 2 \mathrm{CO}_2 (g)$$, what is the mole ratio of ethanol to carbon dioxide?

Accepted Answer

1:2

Stoichiometry and Mole-to-Mole Calculations in GOB Chemistry

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