Thermochemistry MCQs for MDCAT Practice

Chemistry section, Thermochemistry chapter. Up to eight free sample questions, each with the correct answer and a worked explanation. The full chapter opens in the app.

1. Question 1
   Specific heat capacity of a substance X is 4J g−1K−1, its molar mass is 30g/mol. What is its molar heat capacity?
   • A120 Jmol−1K−1 (correct answer)
   • B12 Jmol−1K−1
   • C4 Jmol−1K−1
   • D0.133 Jmol⁻¹K⁻¹
   Correct answer: A

   Convert specific heat capacity (per gram) to molar heat capacity (per mole) using molar mass. Correct answer: 120 Jmol−1K−1.
2. Question 2
   If only the transfer of energy with the surrounding but not matter is possible, it is known as:
   • AOpen system
   • BClosed system (correct answer)
   • CIsolated system
   • DHeterogeneous system
   Correct answer: B

   Understand the thermodynamic definitions of open, closed, and isolated systems based on energy and matter exchange with surroundings.
3. Question 3
   The equation qr = ΔH represents:
   • AHeat changes at constant pressure. (correct answer)
   • BEnthalpy.
   • CPressure changes at normal pressure.
   • DNone of the above.
   Correct answer: A

   The equation $q_r = \Delta H$ signifies that heat exchanged ($q_r$) equals the change in enthalpy ($\Delta H$) under constant pressure conditions.
4. Question 4
   Which of the following is exothermic reaction?
   • ACH4 + 2O2 → CO2 + 2H2O (correct answer)
   • BC+2S → CS2
   • CH2 + I2 → 2HI
   • DNone of the above
   Correct answer: A

   Identify exothermic reactions by recognizing common combustion processes and understanding enthalpy changes based on bond breaking and formation.
5. Question 5
   In thermochemistry, a liquid whose boiling point is to be determined is considered as a/an
   • Afinal state
   • Binitial state
   • Csurrounding
   • Dsystem (correct answer)
   Correct answer: D

   In thermochemistry, the substance whose phase change (like boiling) is being studied is the system, not the surroundings or a specific state.
6. Question 6
   For an exothermic reaction, the energy level of reactant is
   • ALess than the product
   • BMore than the product (correct answer)
   • CEqual to the product
   • DZero
   Correct answer: B

   Exothermic reactions release energy, meaning reactants possess higher energy than products, leading to a negative enthalpy change.
7. Question 7
   CH4 + 2O2 → CO2 + 2H2O. What is the heat of formation of CH4 given:∆Hc (CH4) = -890, ∆Hf (CO2) = -393.5, ∆Hf (H2O) = -285.8?
   • A-76
   • B210
   • C-210 (correct answer)
   • D76
   Correct answer: C

   Apply Hess's Law to calculate the heat of formation of methane using given heats of combustion and formation.
8. Question 8
   Internal energy of a system depends on all the factors EXCEPT:
   • AChemical nature of a substance
   • BTemperature
   • CPressure and volume
   • DPath (correct answer)
   Correct answer: D

   Internal energy (U) is a state function, meaning it depends only on the current state of the system, not the path taken to reach it.

Read the full Thermochemistry chapter notes: Thermochemistry notes. Or browse every chapter.