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Thermodynamics

Short Answer Type

171. What mass of gold of specific heat capacity 0.13 J (°C)^–1 g^–1 can be heated through the same temperature difference when supplied with the same amount of energy as in (a) above?

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172.

Calculate the enthalpy change on freezing of 1.0 mol of water at 10.0°C to ice at –10.0°C.

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173.

Heat capacity at constant pressure is greater than heat capacity at constant volume. Why?

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174.

Derive a relationship between C_pand C_v for an ideal gas.

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Long Answer Type

175.

Define the terms:
(i) Chemical energetics
(ii) Thermochemistry.

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Short Answer Type

176. Why is there energy change in chemical reactions?

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Long Answer Type

177. What do you understand by exothermic and endothermic reactions? Give two examples of each.

(i) Exothermic reactions: Reactions which are accompanied by the evolution of heat energy and have a negative value of ∆H are known as exothermic reactions.e.g.

A negative value of ∆H for exothermic reactions: Heat evolved is equal to the enthalpy change when the reaction is carried out at constant pressure. For an exothermic reaction, there is an evolution of heat energy and hence enthalpy for the products (H_p) will become less than the enthalpy of the reactants (H_R).

(ii) Endothermic reactions: Reactions which are accompanied by absorption of heat energy and have positive value of ∆H are known as endothermic reactions e.g.

A positive value of ∆H for endothermic reactions: Heat absorbed is equal to the enthalpy change when the reaction is carried out at constant pressure. For an endothermic reaction, there is an absorption of heat energy and hence enthalpy of the products (H_p) will become more than the enthalpy of the reactants (H_R).