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 27 of 37
- A. Unity value
- B. Positive value
- C. Zero value
- D. Negative value
Explanation: Explanation for this question will be added soon!
Correct answer: Negative value- A. ∆E = q+ RT
- B. ∆E = q+w
- C. ∆E= ∆H
- D. ∆E, = q+ ∆NP
Explanation: The first law of thermodynamics is given as ΔE=q+w, where ΔE is the change in internal energy of a system, q is the net heat transfer (the…
Correct answer: ∆E = q+w- A. 1 atm and 273 K
- B. 1 atm and 0 K
- C. 1 atm and 298 K
- D. 1 atm and -273°C
Explanation: The conditions for standard enthalpy changes are 1atm pressure and 250C or 298K temperature.
Correct answer: 1 atm and 298 K- A. Liquid only
- B. Solid only
- C. Gases
- D. Liquids and solids
Explanation: In case of liquids and solids, the changes in state do not cause significant volume change i.e. ∆V = 0.
Correct answer: Liquids and solids- A. ΔP
- B. ΔS
- C. ΔE
- D. ΔG
Explanation: At constant volume, the heat of reaction (ΔH) is represented by the change in internal energy (ΔE) of the system.
Correct answer: ΔE- A. Hess's law
- B. Law of mass action
- C. Law of conservation of energy
- D. Law of conservation of mass
Explanation: First law of thermodynamics is also called law of conservation of energy ,hence this option is correct.
Correct answer: Law of conservation of energy- A. x
- B. x - y
- C. x + y
- D. y
Explanation: Energy difference between products and reactants is x and activation energy of reactants is y so in reverse reaction where products will…
Correct answer: x + y- A. ∆H = ∆E
- B. ∆H > ∆E
- C. ∆H < ∆E
- D. ∆H = 0
Explanation: In case of liquids and solids, the changes in state do not cause significant volume change i.e. ∆V = 0.
Correct answer: ∆H = ∆E- A. 0 K
- B. 298 K
- C. 273 K
- D. 0 °C
Explanation: Standard enthalpy (ΔH ) for 1 mole of a substance in its natural state at 1 atm pressure is typically measured at 298 K (25°C).
Correct answer: 298 K- A. Less than ∆H
- B. Zero
- C. Mole than ∆H
- D. Equal to ∆H
Explanation: Non spontaneous processes are endothermic process.few examples are:(i) Pumping of water uphill(ii) Transfer of heat from cold interior…
Correct answer: Mole than ∆H- A. Fusion
- B. Vaporization
- C. Option C
- D. Sublimation
Explanation: Sublimation is a phase transition in which a substance changes directly from a solid to a gas without passing through the liquid phase.
Correct answer: Sublimation- A. 57.0 kJ
- B. 60 kJ
- C. 5.7 kJ
- D. unpredictable
Explanation: All the reactants and products must be in their standard physical states.
Correct answer: 57.0 kJ533. Enthalpy means
- A. Disorder
- B. Transition state
- C. Rate constant
- D. Heat content
Explanation: H = E + PV.Enthalpy is a state function. Also known as heat content.It is measured in joules.
Correct answer: Heat content- A. -394 kJ/mol
- B. +394 kJ/mol
- C. -294 kJ/mol
- D. -390 kJ/mol
Explanation: Fact: The formation of CO2 from carbon and oxygen, is an exothermic reaction, meaning it releases heat.
Correct answer: -394 kJ/mol- A. Pressure
- B. Volume
- C. Temperature
- D. Mass
Explanation: Work Done = PΔV (where P is pressure and ΔV is change in volume {V2 - V1}at constant volume V2 = V1∴ ΔV = V1 - V1 => ΔV = 0.Work done = P…
Correct answer: Volume- A. +285.5 KJ/mol
- B. Zero kJ/mol
- C. -285.5 kJ/mol
- D. 1 kJ/mol
Explanation: ΔH is the heat change in the system. It is calculated by subtracting the sum of energy in reactants from the sum of energy in the…
Correct answer: +285.5 KJ/mol- A. -676 kJ mol-I
- B. -110 kJ mol
- C. 110 kJ mol-1
- D. 676 kJ mol-1
Explanation: According to the Hess' Cycle drawn below:ΔH CO (eqn 2) + ΔH CO2 (eqn 3) = ΔH CO2 (eqn 1),ΔH CO + (-283) = -393.7,ΔH CO = -393.7 - (-283) =…
Correct answer: -110 kJ mol- A. Enthalpy of atomization
- B. Enthalpy of decomposition
- C. Enthalpy formation
- D. Enthalpy of the dissociation
Explanation: Enthalpy change of atomisation is when one mole of a gaseous atom is formed from its element in its standard state, under standard…
Correct answer: Enthalpy of atomization539. ∆Hr of compound is:
- A. Zero in standard state
- B. Always negative
- C. Always positive
- D. sometimes positive and sometimes negative
Explanation: In an exothermic reaction, heat energy is released from the compound, therefore ∆Hr is negative.
Correct answer: sometimes positive and sometimes negative- A. Pressure
- B. Volume
- C. Composition
- D. Mass
Explanation: C = Q / (ΔT × m) where:C = heat capacity,Q = heat energy,ΔT = change in temperature,m = mass.This formula shows that heat capacity depends…
Correct answer: Mass