We know that the relationship between ${\mathrm{K}}_{\mathrm{c}}$ and ${\mathrm{K}}_{\mathrm{p}}$ is

${\mathrm{K}}_{\mathrm{p}}={\mathrm{K}}_{\mathrm{c}}{\left(\mathrm{RT}\right)}^{∆\mathrm{n}}$

What would be the value of $∆\mathrm{n}$ for the reaction?

${\mathrm{NH}}_{4}\mathrm{Cl}\left(\mathrm{s}\right)⇌{\mathrm{NH}}_{3}\left(\mathrm{g}\right)+\mathrm{HI}\left(\mathrm{g}\right)$

(1) 1

(2) 0.5

(3) 1.5

(4) 2

Hint: $∆{\mathrm{n}}_{\mathrm{g}}$ =  number of gaseous molecules of products - number of gaseous molecules of reactants.

The relationship between ${\mathrm{K}}_{\mathrm{c}}$ and ${\mathrm{K}}_{\mathrm{p}}$ is

${\mathrm{K}}_{\mathrm{p}}={\mathrm{K}}_{\mathrm{c}}{\left(\mathrm{RT}\right)}^{∆\mathrm{n}}$

where, $∆\mathrm{n}=$(number of moles of gaseous products)-(number of moles of gaseous reactants)

For solide state reactant or product number of moles is constant and we did not include it.

For the reaction,

${\mathrm{NH}}_{4}\mathrm{Cl}\left(\mathrm{s}\right)⇌{\mathrm{NH}}_{3}\left(\mathrm{g}\right)+\mathrm{HI}\left(\mathrm{g}\right)\phantom{\rule{0ex}{0ex}}∆\mathrm{n}=2-0=2$