ECAT Chemistry — Thermochemistry
Thermochemistry is part of the Chemistry section of the UET ECAT (30 of the 100 MCQs). It breaks into 2 subtopics, and we hold 28 ECAT-pattern practice MCQs on it, each with a written explanation. Tap a subtopic below to practise just that.
Subtopics (2)
How Thermochemistry is tested
Across the 7 ECAT past papers on ParhaiKrlo, Thermochemistry accounts for 8 questions. It appears in 4 of them, about 2 questions a paper. The heaviest was ECAT Past Paper 07, with 3 questions.
| Paper | Questions |
|---|---|
| ECAT Past Paper 07 | 3 |
| ECAT Past Paper 05 | 1 |
| ECAT Past Paper 03 | 2 |
| ECAT Past Paper 02 | 2 |
Thermochemistry MCQs from the ECAT past papers
Try each one before opening the answer. Each comes with a short explanation.
- Q1 · ECAT Past Paper 07 · Thermochemistry
Sodium chloride dissolves in water because:
- A.The hydration energy of its ions is greater than its lattice energy
- B.Its lattice energy is greater than the hydration energy
- C.Its ions are tightly bound in the lattice
- D.The hydration energy is less than the lattice energy
Show answer
Answer: A. The hydration energy of its ions is greater than its lattice energy — Energy released when water molecules hydrate Na⁺ and Cl⁻ is enough to overcome the lattice energy.
- Q2 · ECAT Past Paper 05 · Thermochemistry
The enthalpy change of the reaction NaOH + HCl → NaCl + H₂O is the:
- A.Heat of reaction (general)
- B.Heat of neutralization
- C.Heat of fusion
- D.Heat of combustion
Show answer
Answer: B. Heat of neutralization — An acid reacting with a base to give salt and water releases the heat of neutralization (−57.3 kJ/mol).
- Q3 · ECAT Past Paper 03 · Thermochemistry
In an endothermic reaction, the enthalpy (heat content) of the products is:
- A.Greater than that of the reactants
- B.The same as that of the reactants
- C.Less than that of the reactants
- D.Usually greater than that of the reactants
Show answer
Answer: A. Greater than that of the reactants — Heat is absorbed, so the products end up with more enthalpy: ΔH = H(products) − H(reactants) > 0.