EmSAT Achieve (UAE) · Chemistry

Chemical Reactions, Equilibrium and Thermochemistry

26 practice questions, each with the answer and an explanation.

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Random questions from this topic, one at a time. You see the answer and the explanation straight after each one.

All 26 questions

  1. What is the pH of a 0.0050 M aqueous solution of barium hydroxide, Ba(OH)₂, assuming complete dissociation?
  2. For the exothermic equilibrium N₂(g) + 3H₂(g) ⇌ 2NH₃(g) (ΔH = -92 kJ/mol), which change will increase the equilibrium yield of ammonia (NH₃)?
  3. Calculate the standard enthalpy of reaction for: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l), given ΔH°f [CH₄(g)] = -75 kJ/mol, ΔH°f [CO₂(g)] = -394 kJ/mol, and ΔH°f [H₂O(l)] = -286 kJ/mol.
  4. The reaction 2NO(g) + O₂(g) → 2NO₂(g) has the experimental rate law Rate = k[NO]²[O₂]. If the concentration of NO is doubled while [O₂] is halved, how does the initial reaction rate change?
  5. What is the solubility product constant (K_sp) of lead(II) chloride, PbCl₂, if its molar solubility in pure water at 25°C is 1.6 × 10⁻² M?
  6. Which pair of chemical species forms an effective buffer solution when mixed in equimolar amounts?
  7. For a reaction with ΔH = -50 kJ/mol and ΔS = -100 J/(mol·K), at what temperature does the reaction transition between spontaneous and non-spontaneous?
  8. In the balanced redox reaction: 2MnO₄⁻ + 5C₂O₄²⁻ + 16H⁺ → 2Mn²⁺ + 10CO₂ + 8H₂O, what is the oxidizing agent and how many electrons are transferred per mole of MnO₄⁻?
  9. How does adding a positive catalyst affect a chemical reaction?
  10. What is the IUPAC systematic name for the organic compound with formula CH₃–CH(CH₃)–CH₂–CHO?
  11. What is the standard cell potential (E°_cell) for the galvanic cell: Zn(s) | Zn²⁺(aq) || Cu²⁺(aq) | Cu(s), given E°(Cu²⁺/Cu) = +0.34 V and E°(Zn²⁺/Zn) = -0.76 V?
  12. A 0.10 M solution of a weak monoprotic acid HA has a dissociation constant Ka = 1.0 × 10⁻⁵. What is the approximate hydronium ion concentration [H₃O⁺]?
  13. Which of the following organic reactions converts propene into propane?
  14. For a first-order chemical reaction with rate constant k = 0.0693 min⁻¹, what is the half-life of the reaction?
  15. What happens to the position of equilibrium when the volume of the reaction container is halved for the system: 2SO₂(g) + O₂(g) ⇌ 2SO₃(g)?
  16. Which salt produces a basic aqueous solution when dissolved in pure water?
  17. What functional group is present in the molecule ethyl ethanoate (CH₃COOCH₂CH₃)?
  18. During a calorimetry experiment, 50.0 g of water absorbs 4186 J of heat. By how much does the water temperature rise? (Specific heat of water = 4.184 J/(g·°C))
  19. What is the conjugate acid of the hydrogen phosphate ion, HPO₄²⁻?
  20. Under standard conditions, a spontaneous electrochemical cell always has which combination of thermodynamic signs?
  21. What is the general molecular formula for non-cyclic, saturated alkanes containing n carbon atoms?
  22. In a titration of 25.0 mL of 0.10 M HCl with 0.10 M NaOH, what is the pH of the solution at the equivalence point at 25°C?
  23. Which factor will shift the numerical value of the equilibrium constant K_c for an elementary reaction?
  24. What is the major product formed when ethanol (CH₃CH₂OH) is heated with excess concentrated sulfuric acid at 170°C?
  25. If a reaction has a positive enthalpy change (ΔH > 0) and a negative entropy change (ΔS < 0), what can be concluded about its spontaneity?
  26. What is the concentration of hydroxide ions [OH⁻] in an aqueous solution with a pH of 9.30 at 25°C?

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