AP CHEMISTRY PRACTICE MIDTERM PRACTICE SET 2026 TESTED QUESTIONS AND CORRECT SOLUTIONS

AP CHEMISTRY PRACTICE MIDTERM
PRACTICE SET 2026 TESTED
QUESTIONS AND CORRECT
SOLUTIONS
◉ In 1.00 mol of potassium zirconium sulfate trihydrate, KaZr(SO4)4 •
3 H2O, there are a 1.81 x 1024 hydrogen atoms
b. 6.02 × 1023 sulfur atoms
c. 2.41 x 1024 potassium atoms
d. 4 moles of oxygen atoms
e. 4 moles of zirconium atoms. Answer: c. 2.41 x 1024 potassium atoms


◉ A student has a 1.0 g sample of each of the following compounds:
NaCI, KBr, and KCL Which of the following lists the samples in order
of increasing number of moles in the sample?
a. NaCI < KCI < KBr
b. NaCI < KBr < KCI
c. KCI < NaCI < KBr
d. KBr < KCI < NaCI. Answer: a. NaCI < KCI < KBr


◉ A student obtains a sample of a pure solid compound. In addition to
Avogadro's number, which of the following must the student know in
order to determine how many molecules are in the sample?
a. Mass of the sample, volume of the sample
b. Mass of the sample, density of the sample

,c. Molar mass of the compound, mass of the sample
d. Molar mass of the compound, density of the sample. Answer: C.
Molar mass of the compound, mass of the sample


◉ According to the information in the table at right, a 1.00 g sample of
which of the following contains the greatest mass of oxygen?
a. Na.O
b. MgO
c. K20
d. CaO. Answer: b. MgO


◉ What differentiates a homogeneous mixture from a pure substance?
a. The composition of a pure substance is fixed
b. A pure substance can be separated into elements by physical means
c. A pure substance is always a compound while mixtures can be
elements or compounds
d. A homogeneous mixture is uniform throughout. Answer: a. The
composition of a pure substance is fixed


◉ A student is given two 10 g samples, each a mixture of only
NaC(sand Cs) but in different proportions. Which of the following
pieces of information could be used to determine which mixture has the
higher proportion of KCI(s)?
a. The volume o each mixure
b. The mass of Cl in each mixture

,c. The number of isotopes of Na and K
d. The reaction or each mixture with water. Answer: b. The mass of Cl
in each mixture


◉ An experiment is performed to measure the mass percent of CaCOs(s)
in eggshells. Five different samples of CaCOss) of known mass react
with an excess of 2.0 M HClag) in identical sealed, rigid reaction
vessels. The
pressure of he gas proouceds measured win a pressure gauge atached o
me reaction vessel, since me
reactions exoteric me reaction system is cooleo to ns onginartemperature
before te pressure is recorded
The experimental dala are used to creale tre Caloraton Iine befou 5 Ca
Coz + 2.0M HCkag)
The experiment is repeated with an eggshell sample, and the
experimental data are recorded in the table below.


The mass percent of CaCOss) in the eggshell sample is closest to
a. 30%
b. 45%
c. 60%
d. 75%. Answer: d. 75%


◉ The percentage of silver in a solid sample is determined
gravimetrically by converting the silver to Ag aq) and precipitating it as

, silver chlonde. Failure to do which of the following could cause errors in
the analysis?


I Account for the mass of the weighing paper when the mass of the
sample
II Measure the temperaure during the preciptation reaction
III wash me precipitate
IV Heat the AgCI precipitate to constant mass
a. I only
b. I and Il
c. I and IV
d. I and III
e. I, III and IV. Answer: e. I, III and IV


◉ A 5.0 g sample of MgCl2 may contain measurable amounts of other
compounds as impurities. Which of the following quantities is (are)
needed to determine that the sample is pure MgCI2?
a. The color and density of the sample
b. The mass of Mg in the sample only
c. The number of moles of Cl in the sample only
d. The mass of Mg and the mass or clin the sample. Answer: d. The
mass of Mg and the mass of Cl the sample


◉ To gravimetrically analyze the silver content of a piece of jewelry
made from an alloy of Ag and Cu, a student dissolves a small pre-