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 21 of 37
- A. Better yield
- B. Lower yeild
- C. Lower rate
- D. Cost change
Explanation: Increasing the pressure increases the yield in Haber's process because the number of moles of products is less than the number of moles of…
Correct answer: Better yield- A. E = q + w
- B. E = w-q
- C. E = q -PV
- D. E = q +PV
Explanation: Option A (E = q + w) is the correct equation because it accounts for both the heat added to the system (q) and the work done on or by the…
Correct answer: E = q + w- A. Reactants are reactive
- B. Reactants are stable
- C. Products are reactive
- D. Products are stable
Explanation: The reversibility of a reaction is determined by the reactivity of the products.
Correct answer: Products are reactive404. Volume is a:
- A. Intensive property
- B. Entropy
- C. Path function
- D. Isolated system
- E. State function
Explanation: A s tate function is a property of a system that depends only on its current state, rather than the path taken to reach that state.
Correct answer: State function- A. Photosynthesis
- B. Synthesis of NH3
- C. Nuclear fission
- D. Oxidation of sulfur gases
- E. Burning of fuel and coal
Explanation: Photosynthesis is an endothermic process. During photosynthesis, plants absorb light energy from the sun and convert it into chemical…
Correct answer: Photosynthesis- A. Reactants and products is equal
- B. Reactants is more than that of products
- C. Products is more than that of reactants
- D. Reactants & Products will not change
Explanation: This is the correct statement. In endothermic reactions, the products have greater energy (or heat content) than the reactants because…
Correct answer: Products is more than that of reactants407. All of the following steps are used to calculate the lattice energy in the Born-Haber cycle EXCEPT:
- A. Atomizing the metal
- B. lonizing the metal
- C. Deionize the metal
- D. lonize non metal
Explanation: Deionizing metal is not part of the Born-Haber cycle. It would involve turning ions back into atoms, which is not necessary for…
Correct answer: Deionize the metal- A. Enthalpy of formation
- B. Enthalpy of reaction
- C. Enthalpy of combustion
- D. Enthalpy of neutralization
Explanation: The enthalpy of neutralization is the specific enthalpy change when one mole of water is formed from the reaction of an acid and a base…
Correct answer: Enthalpy of neutralization- A. bond energy
- B. enthalpy change
- C. heat of sublimation
- D. internal energy change
Explanation: At constant volume, the change in internal energy (ΔU) of a system can be expressed using the heat added to the system and the work done.
Correct answer: internal energy change- A. delta E =0
- B. delta E = q+p
- C. delta E = q+ PdeltaV
- D. delta E = qv
Explanation: The equation ΔE=QV relates the change in internal energy (ΔE) of a system at constant volume to the heat added or removed from the system…
Correct answer: delta E = qv- A. Arrhenius' Law
- B. Born Haber's Law
- C. Dalton's Law
- D. Hess's Law
Explanation: Hess's Law states that the total enthalpy change of a reaction is the same, regardless of the pathway taken.It allows you to find the…
Correct answer: Hess's Law- A. -10 atm.dm3
- B. -5 atm.dm3
- C. 5 atm.dm3
- D. 10 atm.dm3
Explanation: W=-PΔVΔV is 20-15 =5dm3 W=- 2atm x 5dm3 =-10atm.dm3
Correct answer: -10 atm.dm3- A. 6010.20J
- B. 6015.20J
- C. 6020.20J
- D. 6025.20J
Explanation: ΔE=q−PΔVΔV=Vwater −Vice =0.018dm3 −0.020dm3 =−0.002dm3PΔV=(1atm)×(−0.002dm)=−0.002dm3atmPΔV=−0.002dm3⋅atm×101.33J/(dm3⋅atm)=−0.20266JΔE=q−P…
Correct answer: 6025.20J- A. 158kcal
- B. 173kcal
- C. 201kcal
- D. 218kcal
Explanation: Energy from carbohydrates=20g×4kcal/g=80kcalEnergy from protein=10g×4kcal/g=40kcalEnergy from fat=9g×9kcal/g=81kcalTotal energy=Energy…
Correct answer: 201kcal- A. Avogadro's law
- B. Faraday's Law
- C. Gas's Law
- D. Hess's Law
Explanation: Hess's Law states that the total enthalpy change during a chemical reaction is the same, regardless of whether the reaction occurs in one…
Correct answer: Hess's Law- A. -679.3
- B. -669.5
- C. 669.5
- D. 679.3
Explanation: By applying Hess's lawΔHf=ΔHsubl+ΔHdiss+ΔHIE+ΔHEA+U (U is the lattice energy)The lattice energy of KBr is approximately 679.35 kJ/mol (the…
Correct answer: -679.3- A. Milk
- B. Ghee
- C. Butter
- D. Glucose
Explanation: Correct. Milk has a lower fat content compared to ghee and butter, and a lower carbohydrate content compared to glucose, resulting in…
Correct answer: Milk- A. The temperature of system drops
- B. Heat flows from surrounding to system:
- C. Heat flows from system to surrounding.
- D. No flow of heat between system to surrounding
Explanation: This is the definition of an endothermic process. The system absorbs heat, so q is positive.
Correct answer: Heat flows from surrounding to system:- A. 4.184
- B. 10.26
- C. 20.92
- D. 25.65
Explanation: 5 calories * 4.184 Joules/calorie = 20.92 Joules.
Correct answer: 20.92- A. cc
- B. ∘C
- C. J
- D. Pa
Explanation: Enthalpy is a form of energy, so its units are Joules (J).
Correct answer: J