AP Chemistry Unit 4 Practice Test 2025 (Chemical Reactions)

Last Updated on January 15, 2025

AP Chemistry Unit 4 Practice Test 2025 (Chemical Reactions). For free, you can try our sample questions and answers on the Unit 4: Chemical Reactions AP Chemistry exam. You can find or practice multiple-choice questions and Answers and Free-Response Questions here. This unit is 7–9% of the Advanced Placement (AP) Exam score.

These multiple-choice questions are based on the Introduction for Reactions, Net ionic equations, Representations of Reactions, Physical and Chemical Changes, and Stoichiometry Types of Chemical Reactions.

Table of Contents

AP Chemistry Unit 4 Practice Test

AP Chemistry Unit 4: Chemical Reactions

Total Items: 20 (Multiple Choice Questions)

Unit 4: Chemical Reactions

You’ll learn how to differentiate physical and chemical processes, and how to measure and express chemical reactions via chemical equations.

Topics may include:

Introduction for reactions
Net ionic equations
Representations of reactions
Physical and chemical changes
Stoichiometry
Types of chemical reactions

On The Exam

7%–9% of exam score

1 / 20

Which two atoms form ions with the same 1s² 2s² 2p⁶ electron configuration?

(A) Cl and Na

(B) Cl and F

(D) S and Br

2 / 20

Which of the following pairs of compounds is expected to have the compound with largest solubility listed first?

(A) MgCl₂ and AlBr₃

(B) CaF₂ and MgS

(D) Al₂O₃ and Cr₂O₃

3 / 20

Which substance is expected to have the largest distance between its nuclei?

(A) NaF

(B) NaCl

(D) NaBr

4 / 20

Which of the following ions are isoelectronic to (have the same electron configuration as) neon?

(A) F⁻

(B) Ga³⁺

(D) All of these are isoelectronic to neon.

5 / 20

When ammonium carbonate, (NH₄)₂CO₃, is dissolved in water, the ions formed are

(A)

(B)

(C)

(D)

6 / 20

When lead(II) nitrate is mixed with potassium chloride, which of the following representations illustrates the correct ratios and solubility of the products?

(A)

(B)

(C)

(D)

7 / 20

Which compound, made from the indicated pairs of ions, is expected to be the least soluble based on coulombic attractive forces?

(A) Iron(III) and nitride ion because both ions have 3 charges of opposite sign

(B) Bromide ion and sodium ion because both ions have single charges of opposite sign

(D) Bromide ion and iron(III) because one ion with a +3 charge is attracting three ions each with a –1 charge

8 / 20

Which of the following will act as a driving force for a chemical reaction?

(A) Formation of a gas that bubbles out of solution

(B) Formation of a weak electrolyte that removes two ions from solution

(D) All of these are driving forces

9 / 20

What are the spectator ions that do not participate in the net ionic equation when solutions of potassium dichromate (K2Cr₂O₇) and lead nitrate (Pb(NO₃)₂) are mixed?

(A) Pb²⁺ and K⁺

(B) Cr²⁺ and NO₃⁻

(D) K⁺ and NO₃⁻

10 / 20

What is the correct formula for aluminum sulfate?

(A) Al₃(SO₄)₂ where the subscripts were chosen to match the ion charges

(B) AlSO₄ since ionic compounds are in 1 to 1 ratios of the ions

(D) Al₂(SO₃)₃ where the subscripts were chosen so the positive charge and negative charge add to zero

11 / 20

What is the net ionic equation for the following reaction that takes place in aqueous solution?

CrCl₃ + Pb(BO₃)₂ → PbCl₂ + Cr(NO₃)₃

(A) Cr²⁺(aq) + Pb²⁺(aq) → CrPb(s)

(B) Cr³(aq) + 3NO₃(aq) → Cr(NO₃)₃(s)

(D) Pb(NO₃)(s) + 2Cl−(aq) → PbCl₂(s) + 2NO₃(aq)

12 / 20

Which of the following molecular views does NOT violate the law of conservation of matter?

(A)

(B)

(C)

(D)

13 / 20

Gaseous hydrogen and nitrogen gas are reacted to form ammonia. Which of the following molecular views shows the correct stoichiometry for this reaction?

(A)

(B)

(C)

(D)

14 / 20

Which of the following is NOT true of a net ionic equation?

(A) All of the nonreacting (spectator) ions have been canceled.

(B) It shows the actual reactants in an equation.

(D) It is used to determine which compounds are insoluble.

15 / 20

Which of the following molecular representations shows pairs of substances undergoing a reaction often classified as single replacement?

(A)

(B)

(C)

(D)

16 / 20

Which of the following is a correct formula?

(A) KH₂PO₄

(B) CaC₂H₃O₂

(D) Ba(CO₃)₂

17 / 20

Which of the following is NOT a correct chemical formula and why

(A) SrBr₂; strontium has only ions with a +1 charge

(B) Ca₂O₃; the charges for the ions do not add up to zero

(D) Na₂S; sodium cannot bond with sulfur

18 / 20

Which of the following reactions is a decomposition reaction

(A) 2KClO₃(s) → 2KCl(s) + 3O₂(g)

(B) C₇H₈O₂(l) + 😯₂(g) → 7CO₂(g) + 4H₂O(l)

(D) 6Li(s) + N₂(g) → 2Li₃N(s)

19 / 20

The electronic configuration 1s² 2s² 2p⁶ 3s² 3p⁶ corresponds to the electronic configuration of

(A) O2^-

(B) F^-

(D) all of the above

20 / 20

What is the formula and name for an ionic compound formed from aluminum and chlorine?

(A) AlCl, aluminum chloride

(B) Al₃Cl, tri-aluminum chloride

(D) AlCl₃, aluminum chloride

Your score is

Free-Response Questions

The following questions involve stoichiometry problems frequently encountered by the chemist in theoretical and laboratory situations. Use the appropriate stoichiometric methods to answer the following questions.

(a) One beaker holds a solution that contains 4.65 grams of sodium sulfide. A second beaker holds a solution that contains 8.95 grams of lead(II) nitrate. When the two solutions are mixed, what mass of PbS forms?

(b) Perform the calculations to determine the empirical formula of a CHNO compound that is analyzed and found to contain 52.63 percent carbon, 7.02 percent hydrogen, and 12.28 percent nitrogen.

(d) A neutralization reaction uses a 0.125 molar solution of sodium hydroxide to titrate 50.0 mL of an unknown sulfuric acid solution. If the reaction takes 23.5 mL of the sodium hydroxide to completely neutralize the sulfuric acid, what is the molarity of the sulfuric acid solution?

See also:

FREE AP Chemistry Practice Test 2025 Study Guide (PDF)

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