First slide

Hess law of constant summation

Question

Statement I: Heat of sublimation is the sum of heat of fusion and heat of vaporisation.
Statement II : Heat of the reaction or enthalpy change is same whether reaction takes place in one step or in multiple steps.

Easy

A

Statement I and Statement II are true.
B

Statement I is true and statement II is false.
C

Statement I is false and Statement II is true.
D

Statement I and Statement II are false.

Solution

The process of direct conversion of solid into gas is known as Sublimation.
It involves two steps
Solid $\rightarrow$ liquid $\rightarrow$ gas
$\therefore\Delta H_{sublimation}=\Delta H_{fusion}+\Delta H_{vapourization}$
According to Hess law total energy change of a reaction remains same
Whether the reaction involves single step or many steps

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