Stoichiometry

Review Guide

What is stoichiometry?

Multiple Choice

In stoichiometry, chemists are mainly concerned with

A. the types of bonds found in compounds.

B. mass relationships in chemical reactions.

C. energy changes occurring in chemical reactions.

D. the speed with which chemical reactions occur.

Name 2 ways we have used stoichiometry.

What do the coefficients in a chemical equation tell

you?

Assume ideal stoichiometry in the reaction:CH4 + 2O2 CO2 + 2H2O

If you know the mass of CH4, you can calculate

A. only the mass of CO2 produced.

B. only the mass of O2 reacting.

C. only the mass of CO2 + H2O produced.

D. the mass of O2 reacting & CO2 + H2O produced.

Multiple Choice

Which properties must be the same on both sides of

a chemical equation?

Which properties don’t have to be the same on both sides of a chemical

equation?

2C2H6 + 7O2 4H2O + 6CO2

Write 3 mole ratios

2C2H6 + 7O2 4H2O + 6CO2

“For every ___ moles of oxygen and ___ moles of ethane that react, ___ moles of carbon dioxide and ___ moles of water

are formed.”

Multiple Choice

Which mole ratio for the equation 6Li + N2 2Li3N is incorrect?

A. C.

B. D.

1 mol N2

6 mol Li

6 mol Li

2 mol N2

2 mol Li3N

1 mol N2

1 mol N2

6 mol Li

2 mol Li3N

6 mol Li

2C2H6 + 7O2 4H2O + 6CO2

Calculate in your head how many moles of

carbon dioxide are formed if you begin with

8 mols of ethane.

What is a limiting reactant?

Multiple Choice

For the reaction below, how many moles of N2 are required to produce 18 mol NH3?

N2 + 3H2 2NH3

A. 4.5 C. 18

B. 9.0 D. 36

What is an excess reactant?

What is the Limiting Reactant? 2C2H6 + 7O2 4H2O + 6CO2

7.49 mol 24.6 mol

Multiple ChoiceWhat mass of NaCl can be produced by the reaction of 0.75 mol Cl2?

2Na + Cl2 2NaCl

A. 0.75 g C. 44 g

B. 1.5 g D. 88 g

Why is the LR not necessarily the reactant with the least amount of

moles?

Multiple ChoiceWhat mass of CO2 can be produced from 25.0 g

CaCO3 given the decomposition reaction

CaCO3 CaO + CO2

A. 11.0 g C. 25.0 g

B. 22.0 g D. 56.0 g

How many moles of each product can be formed? 2C2H6 + 7O2 4H2O + 6CO2

7.49 mol 24.6 mol

Multiple ChoiceIf a chemical reaction involving substances A and B stops when B is completely used up, then B is referred to as the

A. excess reactant.

B. primary reactant.

C. limiting reactant.

D. primary product.

How many grams of water can be formed? 2C2H6 + 7O2 4H2O + 6CO2

7.49 mol 24.6 mol

Multiple ChoiceIf a chemist calculates the maximum amount of product that could be obtained in a chemical reaction, he or she is calculating the

A. percentage yield.

B. mole ratio.

C. theoretical yield.

D. actual yield.

How many moles excess reactant remain after the reaction?2C2H6 + 7O2 4H2O + 6CO2

7.49 mol 24.6 mol

Short Answer

What data are necessary to calculate the percentage yield of a reaction?

Extended ResponseA student makes a compound in the laboratory and reports an actual yield of 120%. Is this result possible? Assuming that all masses were measured correctly, give an explanation.

Extended ResponseBenzene, C6H6, and hydrogen bromide, HBr, as shown below. When 40.0 g of benzene are reacted with 95.0 g of bromine, 65.0 g of bromobenzene is produc with bromine, Br2, to produce bromobenzene, C6H5Br

C6H6 + Br2 C6H5Br + HBr

a. Which compound is the limiting reactant? b. What is the theoretical

yield of bromobenzene? c. What is the reactant in excess, and how much remains after the reaction is completed? d. What is the percentage yield?