Pre-AP Chemistry Practice Test

1. Question

A student places 2.0 g of an unknown substance in a sealed container with no other contents. The student observes the container for 10 minutes and then draws the two particle diagrams shown to represent his observations of the initial and final states. Which of the following descriptions of the observed change is most consistent with the model?

The unknown substance underwent a phase change from solid to liquid and the mass at the end of the experiment was 2.0 g.
The unknown substance underwent a phase change from solid to liquid and the mass at the end of the experiment was 1.5 g.
The unknown substance underwent a phase change from solid to gas and the mass at the end of the experiment was 2.0 g.
The unknown substance underwent a phase change from solid to gas and the mass at the end of the experiment was 1.5 g.

2. Question

The figure represents three containers of equal volume at the same temperature, each containing a different gas or mixture of gases. Which TWO statements best describe the pressure in the containers?

The pressure in Container 1 is greater than the pressure in Container 2 because the Xe atoms are larger than Ne atoms.
The pressure in Container 1 is equal to the pressure in Container 2 because they have the same number of atoms.
The pressure in Container 3 is twice the pressure in Container 2 because Container 3 has twice the number of atoms.
The pressure in all three containers is the same because the containers are at the same temperature.
The pressure in all three containers is the same because the containers have the same volume.
B and C

3. Question

4Na(s) + O₂ (g) -> 2Na₂O(s)

Sodium oxide is produced by the reaction of sodium metal with oxygen gas. The reaction is represented by the chemical equation above. A chemical reaction is set up with 32 moles of Na and 12 moles of O₂ in a reaction vessel. As the reaction proceeds to completion, the number of moles of Na and O₂ are monitored and plotted on a graph as shown in the figure.

Which of the following best explains the steeper slope of the line that represents moles of Na compared to the line that represents moles of O₂ ?

The initial mass of Na is greater than the initial mass of
For every mole of consumed in the reaction, 4 moles are Na are needed.
The mass of 4 Na atoms is greater than the mass of 1 molecule.
The initial number of moles of Na is greater than the initial number of moles of

4. Question

The figure shows particle diagrams representing a 13M solution of an unknown acid after the acid was added to water. Based on the particle diagrams, which of the following claims about the unknown acid is most likely correct?

The acid is strong because there are 13 moles of acid in every liter of water.
The acid is strong because all the acid molecules dissociate in solution
The acid is weak because it produces only one hydronium ion per acid molecule in solution.
The acid is weak because there are fewer acid molecules than water molecules in the solution.

Pre-AP Chemistry Practice Test