All Free Chemistry MCQs with Answers
Every Chemistry question in the bank, across all chapters, each with the correct answer and a written explanation. Free and unlimited, with no account needed.
13,720 questions · page 524 of 686
- 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 + y10467. For solids and liquids
- 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 kJ10472. 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/mol10474. No work is done at constant
- 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 atomization10478. ∆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 negative10479. Heat capacity depends on:
- 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: Mass10480. By definition, the standard heat of formation of C2H6(g) is the enthalpy change for the reaction:
- A. 2C(s) + 6H(g) ---> C2H6(g)
- B. 2C(g) + 6H(g) ---> C2H6(g)
- C. 2C(s) + 3H2(g) ---> C2H6(g)
- D. 2C2H4(s) + H2(g) ---> C2H6(g)
Explanation: Standard enthalpy of formation is the heat of formation when one mole of a substance is formed from its elements in their standard state…
Correct answer: 2C(s) + 3H2(g) ---> C2H6(g)