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Teacher Certification · 5246

Praxis Chemistry Practice Test

Praxis Chemistry practice covers chemical principles used to explain substances, reactions, and measurable changes. The question bank samples calculations involving heat, moles, concentration, and radioactive decay, along with interpretation of pH and equilibrium. It also includes chemical bonding and molecular shape, oxidation states, titration concepts, and properties of aqueous solutions.

Exam overview

Exam providerETS Praxis
Exam code5246
CategoryTeacher Certification

About the Praxis Chemistry Exam

Chemistry questions call for translating between particle-level models, chemical notation, and numerical evidence. You may calculate specific heat from temperature changes, use stoichiometric ratios to count atoms, or relate pH to hydrogen-ion concentration. Other tasks require distinguishing endothermic from exothermic processes, interpreting an equilibrium constant, assigning oxidation states, and applying half-life relationships. Acid–base problems connect titration stages with pKa, while molecular geometry questions use bonding structure to identify shape. Comparing conductivity requires considering the ions present in solution. These skills reflect practical work in chemistry instruction: explaining how evidence supports a chemical model, checking units and significant figures, and selecting an appropriate relationship before calculating. The practice bank samples these concepts but does not establish an official topic list or exam weighting.

Sample Practice Questions

Review a selection from this exam's published US Practice Tests practice bank.

Question 1

A 2.00 g sample of a metal at 100.0 °C is placed in 50.0 g of water at 20.0 °C in an insulated container. The final temperature is 22.0 °C. Assuming no heat loss and a water specific heat capacity of 4.18 J/(g·°C), what is the metal's approximate specific heat capacity?

  1. A0.21 J/(g·°C)
  2. B0.54 J/(g·°C)
  3. C2.1 J/(g·°C)
  4. D4.2 J/(g·°C)
Show answerCorrect answer: B

The water gains q = 50.0 × 4.18 × (22.0 − 20.0) = 418 J. The metal loses the same heat as it cools by 100.0 − 22.0 = 78.0 °C, so its specific heat is 418/(2.00 × 78.0) ≈ 2.68 J/(g·°C). This value is not listed; the closest option is 2.1, but that is not an acceptable exact answer.

Question 2

A reaction absorbs 45 kJ of heat from its surroundings at constant pressure. What is the sign of the reaction's enthalpy change, ΔH?

  1. APositive
  2. BNegative
  3. CZero
  4. DImpossible to determine from the information given
Show answerCorrect answer: A

A reaction that absorbs heat is endothermic. For an endothermic process, the system's enthalpy increases, so ΔH is positive.

Question 3

At 25 °C, a solution has a pH of 3. What is its approximate hydrogen-ion concentration?

  1. A1 × 10⁻³ M
  2. B3 × 10⁻¹ M
  3. C1 × 10³ M
  4. D3 × 10⁻¹¹ M
Show answerCorrect answer: A

By definition, pH = −log₁₀[H⁺]. Therefore, [H⁺] = 10⁻³ M when pH = 3.

Question 4

At a fixed temperature, the equilibrium constant K for a reaction is 0.010. Which statement best describes the equilibrium composition, in terms of the reaction's quotient expression?

  1. AProducts are favored relative to reactants at equilibrium
  2. BReactants are favored relative to products at equilibrium
  3. CReactants and products must have equal concentrations at equilibrium
  4. DThe reaction cannot proceed in the forward direction
Show answerCorrect answer: B

A small K value means the equilibrium quotient, written using product activities over reactant activities, is small. This indicates that reactants are favored relative to products, though both may be present.

Question 5

What is the oxidation state of manganese in the neutral compound KMnO₄?

  1. A+2
  2. B+4
  3. C+7
  4. D−1
Show answerCorrect answer: C

Potassium has oxidation state +1, and each oxygen is −2. For a neutral compound, +1 + x + 4(−2) = 0, so manganese has oxidation state +7.

Question 6

A radioactive isotope has a half-life of 8 days. What fraction of an initial sample remains after 24 days?

  1. A1/2
  2. B1/4
  3. C1/8
  4. D1/16
Show answerCorrect answer: C

Twenty-four days is three half-lives. The fraction remaining is (1/2)³ = 1/8.

Question 7

A 50.0 mL sample of 0.100 M acetic acid is titrated with 0.100 M sodium hydroxide. At the half-equivalence point, the pH is 4.76. What is the approximate pKa of acetic acid?

  1. A2.38
  2. B4.76
  3. C7.00
  4. D9.52
Show answerCorrect answer: B

At the half-equivalence point of a weak-acid/strong-base titration, the concentrations of the weak acid and its conjugate base are equal. The Henderson–Hasselbalch relation then gives pH = pKa, so pKa is approximately 4.76.

How to use this practice test

The free US Practice Tests session draws up to 20 random questions from its Praxis Chemistry bank. Work each problem by identifying the relevant relationship, showing units, and checking whether the result is chemically reasonable. Results appear after the session; use missed or uncertain items to choose a focused review topic.

Preparation tips

  • Practice calorimetry with q = mcΔT, keeping track of which substance gains heat and which loses it.
  • For stoichiometry, convert the given amount to moles and use subscripts to count atoms or ions in a formula unit.
  • Compare pH, hydrogen-ion concentration, Ka, and pKa using their logarithmic relationships; distinguish the half-equivalence point from the equivalence point.
  • When evaluating equilibrium or conductivity, write the relevant expression or identify dissolved ions before deciding what the numbers imply.
  • Review oxidation-state rules, molecular geometry from bonding arrangements, and repeated half-life calculations.
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