AP Chemistry: Chemical Reactions & Stoichiometry 3

Question 1

Which type of reaction is 2H2O2 -> 2H2O + O2?

Accepted Answer

Decomposition

Answer

One compound breaks down into two simpler products, defining decomposition.

Question 2

In a limiting reactant problem, 3 mol H2 react with 2 mol N2 to form NH3 (N2 + 3H2 -> 2NH3). Which is limiting?

Accepted Answer

H2

Answer

3 mol H2 only needs 1 mol N2, but each requires 3 mol H2 per N2; H2 runs out first making it limiting.

Question 3

What is the empirical formula of a compound that is 40.0% C, 6.7% H, and 53.3% O by mass?

Accepted Answer

CH2O

Answer

Moles give a 1:2:1 C:H:O ratio, so the empirical formula is CH2O.

Question 4

How many grams are in 0.250 mol of NaCl (molar mass 58.44 g/mol)?

Accepted Answer

14.6 g

Answer

0.250 mol x 58.44 g/mol = 14.6 g.

Question 5

Which is the correctly balanced equation for the combustion of methane?

Accepted Answer

CH4 + 2O2 -> CO2 + 2H2O

Answer

CH4 + 2O2 -> CO2 + 2H2O balances all C, H, and O atoms.

AP Practice Test