Question

Calculate the degree of dissociation of pcl5 if the vapour density at the give temperature is 70.

Answer 1

Answer:

The molar mass PCl

3

is 137.33 g/mol

The molar mass Cl

2

is 70.6 g/mol

Initial molar mass 2× initial vapour density

=2×104.16=208.32g/mol

Final molar mass =2× final vapour density

=2×62=124g/mol

Let out of 1 mole of PCl

5

present initially, x mole dissociates to form x mole of PCl

3

and x mole of Cl

2

The molar mass of final mixture =124=

1−x+x+x

208.32(1−x)+137.33x+70.6x

124=

1+x

208.32(1−x)+(137.33+70.6)x

124=

1+x

208.32(1−x+x)

124=

1+x

208.32

1+x=

124

208.32

=1.68

x=1.68−1=0.68

The degree of dissociation of PCl

5

at 230

∘

C is

1

0.68

=0.68 or 68 %.

Explanation:

68/