Free Thermochemistry and Energetics of Chemical Reactions MCQs with Answers
728 Thermochemistry and Energetics of Chemical Reactions MCQs from Chemistry, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Thermochemistry measures energy changes in chemical reactions and distinguishes exothermic from endothermic processes. Work covers systems, surroundings and state functions, internal energy, the first law of thermodynamics, enthalpy and Hess's law, including the sign conventions used when heat enters or leaves a system.
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728 questions · page 2 of 37
- A. Endothermic
- B. Exothermic
- C. Thermally unstable
- D. Reversible
Explanation: The symbol in the original stem is the enthalpy change, which did not print cleanly in the paper.
Correct answer: Exothermic- A. -60 kJ
- B. +60 kJ
- C. -140 kJ
- D. +140 kJ
Explanation: By the first law, the change in internal energy is the heat added to the system plus the work done on it, so 100 plus 40 gives plus 140…
Correct answer: +140 kJ- A. Heat of transition
- B. Heat of fusion
- C. Enthalpy change
- D. All of above
Explanation: At constant pressure, the heat absorbed or released by a process is equal to its enthalpy change, q_p = delta H.
Correct answer: Enthalpy change- A. Negative
- B. Positive
- C. May or may not be A or B
- D. none
Explanation: An enthalpy change is the heat change at constant pressure, so it may be positive for an endothermic process or negative for an exothermic…
Correct answer: May or may not be A or B- A. 0 atmosphere
- B. one atmosphere
- C. 2 atmosphere
- D. 10 atmosphere
Explanation: Molar heat of fusion is conventionally measured at constant atmospheric pressure, so the pressure is 1 atmosphere.
Correct answer: one atmosphere- A. glass calorimeter
- B. bomb calorimeter
- C. thermometer
- D. manometer
Explanation: A bomb calorimeter measures heat released by burning a substance in a sealed vessel at constant volume, allowing accurate measurement of…
Correct answer: bomb calorimeter- A. glass calorimeter
- B. manometer
- C. Barometer
- D. thermometer
Explanation: A calorimeter measures the heat absorbed or released by a reaction, and at constant pressure this heat is related to the reaction…
Correct answer: glass calorimeter- A. Endothermic
- B. Exothermic
- C. Fission
- D. Fusion
Explanation: Neutralization of an acid by a base usually releases heat because H+ ions combine with OH− ions to form stable water molecules, making the…
Correct answer: Exothermic- A. Aerosol
- B. Ozone
- C. Acid rain
- D. PAN
Explanation: Acid rain contains sulfuric and nitric acids that lower soil pH and can damage soil organisms and nutrients, making it a cause of soil…
Correct answer: Acid rain- A. 30 KJ
- B. 1 KJ
- C. 39 KJ
- D. 29 KJ
Explanation: Fat supplies approximately 39 kJ of energy per gram when metabolised, so 1 g fat releases about 39 kJ and option c is correct.
Correct answer: 39 KJ- A. Reaction is exothermic
- B. It is insoluble in water
- C. Dilute acid is produced
- D. All of above
Explanation: Sulphur trioxide reacts with water very vigorously and exothermically, producing a fine mist of sulphuric acid that is difficult to…
Correct answer: Reaction is exothermic- A. Exothermic
- B. Moderate reaction
- C. No reaction
Explanation: If the reactants have more energy than the products, the energy difference is released to the surroundings as heat, making the reaction…
Correct answer: Exothermic- A. dry zone burning zone decomposition zone cooling zone
- B. cooling zone burning zone decomposition zone dry zone
- C. burning zone cooling zone decomposition zone
- D. dry zone decomposition zone burning zone cooling zone
Explanation: In a rotary kiln, the material first loses moisture in the dry zone, then limestone decomposes in the decomposition zone, and finally the…
Correct answer: dry zone decomposition zone burning zone cooling zone- A. roasted calcareous material
- B. roasted argillaceous material
- C. roasted calcareous and argillaceous material
- D. roasted gypsum
Explanation: Clinker forms when the calcareous material, mainly limestone, and argillaceous material, containing clay and silica, are heated together…
Correct answer: roasted calcareous and argillaceous material- A. vlay
- B. marine shells
- C. slate
- D. blast furnace slag
Explanation: Argillaceous materials are rich in silica and alumina and include clay, slate and some industrial slags.
Correct answer: marine shells- A. to dry the moisture of slurry
- B. to decompose lime stone to unslaked lime
- C. combination of different oxides like CaO SiO2 Fe2O3 and Al2O3
- D. to reduce the impurities
Explanation: The burning zone reaches a high enough temperature for CaO, SiO2, Al2O3 and Fe2O3 to react and form the clinker compounds of cement.
Correct answer: combination of different oxides like CaO SiO2 Fe2O3 and Al2O3- A. 75% lime stone and 25% clay
- B. 25% lime stone and 75% clay
- C. 15% lime stone and 55% clay
- D. 55% lime stone and 15% clay
Explanation: The usual cement raw mix contains approximately 75% calcareous material, mainly limestone, and 25% argillaceous material, mainly clay.
Correct answer: 75% lime stone and 25% clay- A. crushing heating mixing grinding
- B. crushing mixing heating grinding and mixing
- C. crushing grinding mixing heating
- D. mixing heating grinding crushing
Explanation: Cement manufacture proceeds by crushing the raw materials, grinding them, mixing the ground material to obtain a uniform composition, and…
Correct answer: crushing grinding mixing heating- A. Lime (CaO)
- B. Silica (SiO2)
- C. Alumina (Al2O3)
- D. Magnesia (MgO)
Explanation: Calcium oxide is the major oxide in ordinary Portland cement because limestone is the largest part of the raw mix and decomposes to CaO on…
Correct answer: Lime (CaO)- A. clay and clinker
- B. clay lime stone and gypsum
- C. lime stone and gypsum
- D. lime stone and clay
Explanation: In simplified descriptions, cement is made from calcareous material such as limestone, argillaceous material such as clay, and a small…
Correct answer: clay lime stone and gypsum