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All Free Chemistry MCQs with Answers

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13,720 questions · page 519 of 686

10361. Which of the following sets constitutes all the state functions of a system?

  • A. Temperature, Pressure, Work
  • B. Enthalpy, Work, Pressure
  • C. Enthalpy, Entropy, Internal Energy
  • D. Heat, Enthalpy, Volume

Explanation: Enthalpy, Entropy, Internal Energy) - Correct: All three are state functions as they depend only on the state of the system

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Correct answer: Enthalpy, Entropy, Internal Energy

10362. Hydrogen is a diatomic molecule and its molecule have

  • A. Translational motion
  • B. Vibrational motion
  • C. Vibrational and rotational motion
  • D. Translational and vibrational motion

Explanation: Vibrational and rotational motion) - Correct: Hydrogen molecules exhibit both vibrational and rotational motion along with translational…

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Correct answer: Vibrational and rotational motion

10363. Transfer of heat from hot surroundings to a cold refrigerator is an example of:

  • A. Spontaneous reaction
  • B. Non-Spontaneous reaction
  • C. First law of thermodynamics
  • D. All of the above options are correct

Explanation: Spontaneous heat transfer from hot to cold is also known as the second law of thermodynamics.

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Correct answer: Spontaneous reaction

10364. The measurement of heat absorbed or given out in a chemical reaction is referred to as:

  • A. Endothermic reaction
  • B. Exothermic reaction
  • C. Thermochemistry
  • D. Heat of formation

Explanation: Thermochemistry is the branch of chemistry concerned with the quantities of heat evolved or absorbed during chemical reactions.Endothermic…

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Correct answer: Thermochemistry

10365. Cl + e ----> Cl- ΔH = -348kJ/mol The value -348KJ/mol in this case will be:

  • A. Ionization energy
  • B. Electronegativity
  • C. Electron affinity
  • D. Entropy
  • E. Free energy

Explanation: As it can be seen in the equation, electrons are gained by the element chlorine to form a negative ion (anion).

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Correct answer: Electron affinity

10366. For a reaction given below C(s) + O2 (g) -> CO2 (g) + 394 kJ / mol The enthalpy of reaction is

  • A. 394 kJ / mol
  • B. -394 kJ / mol
  • C. 197 kJ / mol
  • D. -197 kJ / mol

Explanation: Formation of Carbon dioxide from Carbon and Oxygen is an exothermic reaction.

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Correct answer: -394 kJ / mol

10367. For a chemical reaction A -> B, the threshold energy of the reaction is 37 kJ/mole. The average internal energy of A is 12 kJ/Mole. What will be the activation energy of A?

  • A. 43 K.J/Mole
  • B. 37 K.J/Mole
  • C. 25 KJ/Mole
  • D. 19 K.J/Mole

Explanation: Since the initial internal energy of reactants in already 12KJ/mol.Threshold energy for reaction to proceed is 37kJ/mol.That means the…

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Correct answer: 25 KJ/Mole

10368. Two rocket fuels below are determined by their high performance. N2H4(l) + O2(g) -> N2(g) + 2H2O(l) ΔH= -632 kJ H2 (g) + ½ O2(g) -> H2O(l) ΔH = -286 kJ If equal masses of hydrazine and hydrogen are used, which of the following has better performance?

  • A. Hydrazine
  • B. Both have equal enthalpy of formation
  • C. Hydrogen gas
  • D. Cannot be compared

Explanation: The performance of rocket fuel is measured by its enthalpy of combustion, which is the amount of heat released when one mole of the fuel…

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Correct answer: Hydrogen gas

10369. Exothermic Reactions heat is

  • A. Taken in
  • B. Give out to surroundings
  • C. Neither given nor lost
  • D. None of these

Explanation: An exothermic reaction is a chemical or physical reaction that releases heat. It gives out energy to its surroundings.

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Correct answer: Give out to surroundings

10370. In an exothermic reaction (reversible), which of the following has a positive value?

  • A. Enthalpy
  • B. Entropy
  • C. Gibb's free energy
  • D. None of these options are correct

Explanation: In an exothermic reversible reaction, the change in Gibbs free energy (ΔG) can have a positive value at lower temperatures due to the…

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Correct answer: Gibb's free energy

10371. On which of the following factors Hydration Energy depend?

  • A. Charge to size ratio
  • B. Polarizability of anions
  • C. Polarization power of Cations
  • D. All of these

Explanation: Hydration energy is the amount of energy released or absorbed when ions in gaseous state are surrounded by water molecules to form…

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Correct answer: All of these

10372. What does it mean, when a reaction is exothermic?

  • A. Energy content of product is more
  • B. Energy content of reactant is less
  • C. Heat is transferred from the system to the surrounding
  • D. Heat is transferred from the surrounding to the system

Explanation: An exothermic reaction is a chemical reaction that releases energy in the form of heat.

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Correct answer: Heat is transferred from the system to the surrounding

10373. Hess law states that the total enthalpy change of a reaction remains same regardless of:

  • A. Route reaction takes completion
  • B. Temperature of reactants
  • C. Concentration of products
  • D. Concentration of reactants

Explanation: Option A is correct since it states the correct definition of Hess's law which is: If a chemical change takes place by several different…

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Correct answer: Route reaction takes completion

10374. Knowledge obtain through thermodynamics is used to explain which of the following property?

  • A. Boiling point.
  • B. Chemical bonding.
  • C. Quantum study.
  • D. Physical properties.

Explanation: Thermodynamics explain chemical bonding. chemical bonding, any of the interactions that account for the association of atoms into…

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Correct answer: Chemical bonding.

10375. The enthalpy change of a reaction which involves the formation of the atom from its elements at S.T.P. is called?

  • A. Enthalpy of formation
  • B. Enthalpy of combustion
  • C. Enthalpy of neutralization
  • D. Enthalpy of sublimation

Explanation: The standard enthalpy of formation of a compound is the amount of heat absorbed or evolved (enthalpy change) when one mole of a compound…

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Correct answer: Enthalpy of formation

10376. In the enthalpy relation, ∆H=(q)p + ∆(PV) the value of ∆(PV) can be neglected for the reactions involving _?

  • A. Gases
  • B. Liquids
  • C. Liquids and solids
  • D. Liquids and Gases

Explanation: In the case of liquids and solids, the changes in the state do not cause significant volume change i.e. ΔV=0.

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Correct answer: Liquids and solids

10377. The process that can both be endothermic and exothermic out of the following is:

  • A. Dissolution
  • B. Crystallization
  • C. Bond breaking
  • D. Condensation

Explanation: The process of dissolving can be endothermic (temperature goes down) or exothermic (temperature goes up).

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Correct answer: Dissolution

10378. To raise the temperature of 2 moles of a diatomic gas by 1°C at constant pressure, the required amount of heat is 120 cal. The amount of heat which goes as the gas's internal energy is almost:

  • A. 82.5 Cal
  • B. 80 Cal
  • C. 85.2 Cal
  • D. 58.8 Cal

Explanation: Option C is correct as Cp and CV for a diatomic gas are 7/2 R and 5/2 R respectively.

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Correct answer: 85.2 Cal

10379. The ΔHf for CO2(g), CO(g) and H2O(g) are −393.5, −110.5 and −241.8 kJ mol−1 respectively. The standard enthalpy change (in kJ) for the reaction, CO2(g) + H2(g) → CO(g) + H2O(g) is:

  • A. 524.1
  • B. 41.2
  • C. −262.5
  • D. −41.2

Explanation: Option B is correct according to the following solution:

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Correct answer: 41.2

10380. How many gram of butane must be burnt to heat 10 kg water from 30°C to 100°C. Heat of combustion of butane is −700 kcal/mol and specific heat of water is 1 cal gm−1 K−1 .

  • A. 58 gm
  • B. 56 gm
  • C. 54 gm
  • D. 52 gm

Explanation: First, let's calculate the heat required to raise the temperature of water from 30°C to 100°C: Heat (Q) = mass (m) × specific heat (c) ×…

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Correct answer: 58 gm
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