EST II CHEMISTRY
HARD PRACTICE MOCK EXAM — 2026 SPECIFICATIONS
60 Questions | 60 Minutes
60 Questions | 60 Minutes
Directions:
Choose the best answer for each question. Each question has five answer choices: A, B, C, D, and E.
This practice test emphasizes application, calculation, chemical reasoning, data interpretation, and conceptual understanding.
Exactly 6 questions involve experimental/laboratory chemistry.
Use common atomic masses when needed:
H = 1, C = 12, N = 14, O = 16, Na = 23, Mg = 24, Al = 27, S = 32, Cl = 35.5, K = 39, Ca = 40, Fe = 56.
For this practice test, use 22.4 L/mol for an ideal gas at STP when required.
Choose the best answer for each question. Each question has five answer choices: A, B, C, D, and E.
This practice test emphasizes application, calculation, chemical reasoning, data interpretation, and conceptual understanding.
Exactly 6 questions involve experimental/laboratory chemistry.
Use common atomic masses when needed:
H = 1, C = 12, N = 14, O = 16, Na = 23, Mg = 24, Al = 27, S = 32, Cl = 35.5, K = 39, Ca = 40, Fe = 56.
For this practice test, use 22.4 L/mol for an ideal gas at STP when required.
ATOMIC THEORY AND CHEMICAL BONDING
1. An atom has 17 protons, 18 neutrons, and 18 electrons. Which statement correctly identifies the particle?
A) A neutral chlorine atom
B) A chlorine ion with a 1− charge
C) An argon ion with a 1+ charge
D) A sulfur ion with a 2− charge
E) A potassium ion with a 1− charge
Answer: B) A chlorine ion with a 1− charge
2. Which electron configuration represents an atom in an excited state?
A) 1s² 2s² 2p⁶
B) 1s² 2s² 2p⁵
C) 1s² 2s² 2p⁶ 3s¹
D) 1s² 2s¹ 2p⁶
E) 1s² 2s² 2p⁶ 3s²
Answer: D) 1s² 2s¹ 2p⁶
3. Two isotopes of the same element must have the same number of:
A) Neutrons
B) Electrons in every possible ion
C) Protons
D) Total nucleons
E) Mass numbers
Answer: C) Protons
4. Which molecule has a linear molecular geometry because the central atom has two bonding regions and no lone pairs?
A) H₂O
B) NH₃
C) CH₄
D) CO₂
E) SO₂
Answer: D) CO₂
5. Which molecule is expected to be polar?
A) CO₂
B) CH₄
C) BF₃
D) CCl₄
E) H₂O
Answer: E) H₂O
6. Which compound contains predominantly ionic bonding?
A) CO₂
B) CH₄
C) NaCl
D) NH₃
E) H₂O
Answer: C) NaCl
7. Which substance can form hydrogen bonds between its molecules?
A) CH₄
B) CO₂
C) H₂O
D) Cl₂
E) CCl₄
Answer: C) H₂O
8. Which statement about metallic bonding best explains why metals conduct electricity?
A) Metal atoms contain permanently charged molecules.
B) Positive ions are surrounded by delocalized electrons that can move.
C) Metal atoms contain only ionic bonds.
D) Metals contain no electrons in their outer shells.
E) Metallic bonds prevent electron movement.
Answer: B) Positive ions are surrounded by delocalized electrons that can move.
CHEMICAL BEHAVIOR — AQUEOUS SOLUTIONS AND GASES
9. What is the molarity of a solution containing 0.50 mol of NaCl in 2.0 L of solution?
A) 0.10 M
B) 0.25 M
C) 0.50 M
D) 1.0 M
E) 2.5 M
Answer: B) 0.25 M
10. A solution contains 20 g of NaOH (molar mass = 40 g/mol) in 500 mL of solution. What is its molarity?
A) 0.25 M
B) 0.50 M
C) 1.0 M
D) 2.0 M
E) 4.0 M
Answer: D) 1.0 M
11. A gas occupies 4.0 L at 1.0 atm. If its temperature remains constant and the pressure becomes 2.0 atm, what is the new volume?
A) 0.5 L
B) 1.0 L
C) 2.0 L
D) 4.0 L
E) 8.0 L
Answer: C) 2.0 L
12. A gas is heated at constant pressure. According to Charles's law, its volume:
A) Decreases as absolute temperature increases.
B) Increases directly with absolute temperature.
C) Remains constant.
D) Becomes inversely proportional to pressure only.
E) Becomes zero at 100°C.
Answer: B) Increases directly with absolute temperature.
13. A mixture of gases has a total pressure of 900 mmHg. Oxygen contributes 180 mmHg. What is the mole fraction of oxygen, assuming ideal behavior?
A) 0.10
B) 0.20
C) 0.40
D) 0.50
E) 0.80
Answer: B) 0.20
14. Which substance is expected to have the greatest solubility in water?
A) A nonpolar hydrocarbon
B) A nonpolar gas
C) An ionic compound that dissociates into ions
D) A nonpolar liquid
E) A substance that cannot interact with water
Answer: C) An ionic compound that dissociates into ions
15. A gas is compressed to half its original volume while temperature remains constant. Which change in particle behavior best explains the pressure increase?
A) Particles become less massive.
B) Particles collide with the container walls more frequently.
C) Particles stop moving.
D) The number of particles doubles.
E) The average kinetic energy becomes zero.
Answer: B) Particles collide with the container walls more frequently.
CHEMICAL REACTIONS
16. What is the pH of a solution with [H⁺] = 1.0 × 10⁻³ M?
A) 1
B) 2
C) 3
D) 10
E) 11
Answer: C) 3
17. Which substance is a strong acid in aqueous solution?
A) CH₃COOH
B) HF
C) HCl
D) NH₃
E) H₂O
Answer: C) HCl
18. Which reaction is an acid-base neutralization?
A) Zn + CuSO₄ → ZnSO₄ + Cu
B) HCl + NaOH → NaCl + H₂O
C) CaCO₃ → CaO + CO₂
D) 2H₂ + O₂ → 2H₂O
E) AgNO₃ + NaCl → AgCl + NaNO₃
Answer: B) HCl + NaOH → NaCl + H₂O
19. According to Brønsted-Lowry theory, an acid is a substance that:
A) Accepts a proton.
B) Donates a proton.
C) Accepts an electron only.
D) Produces OH⁻ only.
E) Must contain oxygen.
Answer: B) Donates a proton.
20. In the reaction HCl + H₂O → H₃O⁺ + Cl⁻, which species acts as the Brønsted-Lowry base?
A) HCl
B) Cl⁻
C) H₂O
D) H₃O⁺
E) H⁺
Answer: C) H₂O
21. In the redox reaction MnO₄⁻ → Mn²⁺, manganese undergoes:
A) Oxidation
B) Reduction
C) Neutralization
D) Precipitation
E) No change in oxidation state
Answer: B) Reduction
22. In the reaction Zn + Cu²⁺ → Zn²⁺ + Cu, which species is the reducing agent?
A) Zn
B) Zn²⁺
C) Cu
D) Cu²⁺
E) Both ions
Answer: A) Zn
23. Which reaction is a precipitation reaction?
A) HCl + NaOH → NaCl + H₂O
B) 2H₂ + O₂ → 2H₂O
C) AgNO₃ + NaCl → AgCl(s) + NaNO₃
D) CaCO₃ → CaO + CO₂
E) CH₄ + 2O₂ → CO₂ + 2H₂O
Answer: C) AgNO₃ + NaCl → AgCl(s) + NaNO₃
24. A titration uses 25.0 mL of 0.20 M HCl to completely neutralize NaOH. Assuming a 1:1 ratio, how many moles of NaOH were present?
A) 0.0020 mol
B) 0.0050 mol
C) 0.010 mol
D) 0.050 mol
E) 0.20 mol
Answer: B) 0.0050 mol
QUANTITATIVE CHEMISTRY
25. How many moles are present in 36 g of H₂O?
A) 0.5 mol
B) 1.0 mol
C) 2.0 mol
D) 18 mol
E) 36 mol
Answer: C) 2.0 mol
26. What is the molar mass of Ca(NO₃)₂?
A) 102 g/mol
B) 124 g/mol
C) 164 g/mol
D) 180 g/mol
E) 204 g/mol
Answer: C) 164 g/mol
27. For the reaction 2H₂ + O₂ → 2H₂O, how many moles of water can theoretically form from 3 mol H₂ with excess O₂?
A) 1.5 mol
B) 2 mol
C) 3 mol
D) 4 mol
E) 6 mol
Answer: C) 3 mol
28. For the reaction N₂ + 3H₂ → 2NH₃, 2 mol N₂ react with 3 mol H₂. Which reactant is limiting?
A) N₂
B) H₂
C) NH₃
D) Neither reactant
E) Both are present in exact stoichiometric amounts.
Answer: B) H₂
29. A reaction has a theoretical yield of 50 g and an actual yield of 40 g. What is the percent yield?
A) 20%
B) 40%
C) 60%
D) 80%
E) 125%
Answer: D) 80%
30. A compound contains 40.0% carbon, 6.7% hydrogen, and 53.3% oxygen by mass. Which empirical formula is most likely?
A) CHO
B) CH₂O
C) C₂H₄O
D) C₂H₆O
E) CH₃O
Answer: B) CH₂O
31. What volume would 0.50 mol of an ideal gas occupy at STP using 22.4 L/mol?
A) 5.6 L
B) 11.2 L
C) 22.4 L
D) 44.8 L
E) 56.0 L
Answer: B) 11.2 L
32. A mixture contains 2 mol nitrogen and 3 mol oxygen. What is the mole fraction of oxygen?
A) 0.20
B) 0.30
C) 0.40
D) 0.60
E) 0.75
Answer: D) 0.60
PERIODIC TABLE AND PERIODIC TRENDS
33. Across a period from left to right, atomic radius generally:
A) Increases because shielding increases greatly.
B) Decreases because effective nuclear charge increases.
C) Remains exactly constant.
D) Becomes zero.
E) Increases because the number of occupied shells increases.
Answer: B) Decreases because effective nuclear charge increases.
34. Which element has the greatest atomic radius?
A) Li
B) Na
C) K
D) Rb
E) Cs
Answer: E) Cs
35. Which element has the greatest electronegativity?
A) C
B) N
C) O
D) F
E) Cl
Answer: D) F
36. Which element is most likely to form a 2− ion?
A) Na
B) Mg
C) Al
D) O
E) Ne
Answer: D) O
37. Which oxide is expected to be the most basic?
A) Na₂O
B) SO₃
C) CO₂
D) Cl₂O₇
E) P₂O₅
Answer: A) Na₂O
38. Which compound is correctly named?
A) Na₂O — sodium oxide
B) CO₂ — carbon monoxide
C) N₂O₅ — nitrogen dioxide
D) FeCl₂ — iron(III) chloride
E) CaCl₂ — calcium chlorate
Answer: A) Na₂O — sodium oxide
CHEMICAL KINETICS, EQUILIBRIUM AND THERMOCHEMISTRY
39. Which change generally increases the rate of a reaction between two solid reactants?
A) Decreasing temperature
B) Increasing particle size
C) Increasing surface area
D) Removing all collisions
E) Decreasing concentration
Answer: C) Increasing surface area
40. A catalyst increases reaction rate primarily by:
A) Increasing the enthalpy change.
B) Increasing the amount of product at equilibrium.
C) Providing an alternative pathway with lower activation energy.
D) Increasing the temperature permanently.
E) Changing the equilibrium constant.
Answer: C) Providing an alternative pathway with lower activation energy.
41. According to collision theory, a successful reaction requires particles to collide with sufficient energy and:
A) Any orientation.
B) Appropriate orientation.
C) Zero kinetic energy.
D) Maximum mass.
E) Identical charges.
Answer: B) Appropriate orientation.
42. For the equilibrium N₂(g) + 3H₂(g) ⇌ 2NH₃(g), increasing the concentration of H₂ will initially:
A) Shift equilibrium toward reactants.
B) Shift equilibrium toward products.
C) Stop the reaction completely.
D) Change the value of K at constant temperature.
E) Remove NH₃ immediately.
Answer: B) Shift equilibrium toward products.
43. For the same equilibrium, increasing pressure favors the side with:
A) More moles of gas.
B) Fewer moles of gas.
C) More solid particles.
D) More liquid particles.
E) Equal numbers of gas molecules only.
Answer: B) Fewer moles of gas.
44. For the equilibrium 2SO₂(g) + O₂(g) ⇌ 2SO₃(g), which expression represents Kc?
A) [SO₂]²[O₂] / [SO₃]²
B) [SO₃]² / ([SO₂]²[O₂])
C) [SO₃] / ([SO₂][O₂])
D) [SO₂][O₂] / [SO₃]
E) [SO₃]²[O₂] / [SO₂]²
Answer: B) [SO₃]² / ([SO₂]²[O₂])
45. An endothermic reaction has ΔH:
A) Less than zero
B) Equal to zero for every reaction
C) Greater than zero
D) Always equal to −100 kJ
E) Unrelated to energy transfer
Answer: C) Greater than zero
46. Which statement correctly describes an exothermic reaction?
A) Heat is absorbed from the surroundings.
B) Products have greater enthalpy than reactants.
C) ΔH is positive.
D) Heat is released to the surroundings.
E) The reaction cannot occur spontaneously.
Answer: D) Heat is released to the surroundings.
47. A reaction has ΔH = −250 kJ. What happens when the reaction occurs as written?
A) 250 kJ is absorbed.
B) 250 kJ is released.
C) 500 kJ is absorbed.
D) No energy is transferred.
E) The reaction must be endothermic.
Answer: B) 250 kJ is released.
EXPERIMENTAL CHEMISTRY — 6 QUESTIONS
48. LAB QUESTION: A student prepares two salt solutions. Solution A is made by dissolving 5.0 g of NaCl in 100 mL of water. Solution B is made by dissolving 10.0 g of NaCl in 100 mL of water. Which conclusion is best supported?
A) Solution A has twice the concentration of B.
B) Solution B has twice the concentration of A.
C) Both have identical concentrations.
D) Solution B contains half as many NaCl particles.
E) Concentration cannot depend on the amount of solute.
Answer: B) Solution B has twice the concentration of A.
49. LAB QUESTION: A student wants to separate a mixture of sand and dissolved sodium chloride in water. Which sequence is most appropriate?
A) Distillation followed by filtration
B) Filtration followed by evaporation
C) Evaporation followed by filtration
D) Chromatography only
E) Sublimation only
Answer: B) Filtration followed by evaporation
50. LAB QUESTION: A student measures the volume of a liquid three times and obtains 24.8 mL, 24.9 mL, and 24.8 mL. The accepted value is 25.0 mL. Which statement is best?
A) The measurements are precise but not perfectly accurate.
B) The measurements are neither precise nor accurate.
C) The measurements are accurate but not precise.
D) The measurements show no consistency.
E) The accepted value must be incorrect.
Answer: A) The measurements are precise but not perfectly accurate.
51. LAB QUESTION: During an acid-base titration, a student accidentally adds several extra drops of NaOH after the indicator changes color. Compared with the true endpoint, the recorded NaOH volume will most likely be:
A) Too small
B) Too large
C) Exactly unchanged
D) Zero
E) Independent of the extra drops
Answer: B) Too large
52. LAB QUESTION: A student heats a solution and records the following data:
| Time (min) | Temperature (°C) |
|---|---|
| 0 | 20 |
| 2 | 32 |
| 4 | 44 |
| 6 | 56 |
Which conclusion is best supported by the data?
A) Temperature decreases at a constant rate.
B) Temperature increases approximately 6°C per minute.
C) Temperature increases approximately 12°C per minute.
D) The temperature remains constant.
E) The solution must be undergoing a phase change.
Answer: B) Temperature increases approximately 6°C per minute.
53. LAB QUESTION: A student reacts magnesium with hydrochloric acid and compares two trials. Trial 1 uses magnesium strips; Trial 2 uses the same mass of finely powdered magnesium. All other conditions are identical. Trial 2 produces hydrogen gas faster. Which explanation is most appropriate?
A) Powdered magnesium has a lower temperature by definition.
B) Powdered magnesium has a greater surface area available for collisions.
C) Powdered magnesium has a different atomic mass.
D) Hydrochloric acid becomes a catalyst automatically.
E) The reaction no longer requires collisions.
Answer: B) Powdered magnesium has a greater surface area available for collisions.
ADVANCED CHEMICAL REASONING
54. A student mixes equal volumes of 0.10 M HCl and 0.10 M NaOH. Assuming complete neutralization, the resulting solution is approximately:
A) Strongly acidic
B) Strongly basic
C) Neutral
D) Pure HCl
E) Pure NaOH
Answer: C) Neutral
55. A reaction initially has a rate of 2.0 mol/L·s. Increasing the reactant concentration causes the rate to become 8.0 mol/L·s. Which factor most directly explains this change?
A) Fewer collisions occurred.
B) More effective collisions occurred per unit time.
C) The activation energy necessarily increased.
D) The equilibrium constant necessarily decreased.
E) The reaction became impossible.
Answer: B) More effective collisions occurred per unit time.
56. Consider the equilibrium: 2NO₂(g) ⇌ N₂O₄(g). NO₂ is brown while N₂O₄ is colorless. If the mixture becomes noticeably lighter after compression, which conclusion is most reasonable?
A) Equilibrium shifted toward NO₂.
B) Equilibrium shifted toward N₂O₄.
C) The reaction stopped.
D) The temperature necessarily increased.
E) NO₂ was converted into oxygen.
Answer: B) Equilibrium shifted toward N₂O₄.
57. A sample contains 0.20 mol of a solute dissolved in 500 g of water. What is the molality?
A) 0.10 mol/kg
B) 0.20 mol/kg
C) 0.40 mol/kg
D) 2.0 mol/kg
E) 2.5 mol/kg
Answer: C) 0.40 mol/kg
58. A 25.0 g sample of CaCO₃ is heated according to: CaCO₃ → CaO + CO₂. What mass of CO₂ can theoretically be produced?
A) 2.2 g
B) 5.5 g
C) 11.0 g
D) 22.0 g
E) 25.0 g
Answer: B) 11.0 g
59. Which change would increase the solubility of most solid solutes in water, assuming the dissolution process is endothermic?
A) Decreasing temperature
B) Increasing temperature
C) Removing solvent
D) Decreasing particle collisions
E) Freezing the solution
Answer: B) Increasing temperature
60. A student obtains 18 g of product from a reaction for which the theoretical yield is 24 g. The student repeats the experiment and obtains 21 g. Which conclusion is best supported?
A) The second experiment has a lower percent yield.
B) The second experiment has a higher percent yield.
C) Both experiments have a 100% yield.
D) The theoretical yield changed automatically.
E) Percent yield cannot be compared.
Answer: B) The second experiment has a higher percent yield.
