Thermodynamics

Chemistry NCERT Exemplar Solutions Class 11th Chapter six 
Standard molar enthalpy of formation is the enthalpy change for the formation of one mole of a compound from its most stable states or reference states. As per the given information in the question, the standard enthalpy for the given equation is – 572 kJ mol^–1

Now the enthalpy of formation for H₂O will be half the enthalpy of the value in the given equation. So now we can calculate that

? _fH? = $\frac{-572\mathrm{}\mathrm{K}\mathrm{J}}{2}$ = -286KJ/mol

This is a Short Answer Type Questions as classified in NCERT Exemplar

As per the information provided in the question, for one mole of CCl₄ (154 g), the heat of vaporisation required is 30.5 kJ/mol .

Hence for the vaporisation of 284 g of CCl₄, we require:

$\frac{284}{154}*30.5$  = 56.2 kJ

This is a Short Answer Type Questions as classified in NCERT Exemplar

Δ_rH? =ΣB.E _(reactant)-ΣB.E _(product)

 =B.E._H2 + BE_BR2 -2 *B.E>_HBr

= 435+192-2 (*368)

= 109KJmol^-1

43. A process which can take place of its own or initiate under some conditions. For example: Common salt dissolves in water of its own.

42. ?G = ?H – T?S

Where ?G = free energy change.

?H = enthalpy change.

?S = entropy change.

41. Amount of heat required to vapourize one mole of a liquid at constant temperature and under standard pressure (1bar) is called its standard enthalpy of vapourization or molar enthalpy of vapourization, Δ_vapH^?.

40. (i) First law of thermodynamics: It states that energy can neither be created nor be destroyed. The energy of an isolated system is constant.
?u = q + w

(ii) The standard enthalpy change for the formation of one mole of a compound from its elements in their most stable states of aggregation (also known as reference state is called Standard Molar Enthalpy of Formation. Its symbol is Δ_f H^?, where the subscript ' f ' indicates that one mole of the compound in question has been formed in its standard state from its elements in their most stable states of aggregation.

39. In thermodynamics, a distinction is made between extensive properties and intensive properties. An extensive property is a property whose value depends on the

quantity or size of matter present in the system. For example, mass, volume, internal energy, enthalpy, heat capacity, etc. are extensive properties.

Those properties which do not depend on the quantity or size of matter present are known as intensive properties. For example, temperature, density, pressure etc. are intensive properties.

38. Since, there is an increase in the number of moles on the product side so, entropy increases and ?S is positive.