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  • The degree of dissociation of PCl5 is 60%,then find out the observed molar mass of the mixture.Option: 1 130.3<div clas

The degree of dissociation of PCl5 is 60%,then find out the observed molar mass of the mixture.

Option: 1

130.3


Option: 2

135


Option: 3

229.5


Option: 4

206.5


Answers (1)

best_answer

Asking observed molar mass 

we know this formula

Theoretical moles X Theoretical molar mass = Observed moles X Observed molar mass

for solving we have to find other values.

Below I have given the process.

We have been given that the degree of dissociation is 60% means 60/100 =0.6

                    \mathrm{PCl}_{5(\mathrm{g})} \rightleftharpoons \mathrm{PCl}_{3(\mathrm{g})}+\mathrm{Cl}_{2(\mathrm{g})}?
Initial moles      1                     0                  0
At equilibrium   1-\alpha?                  \alpha?                  \alpha?
Where, \alpha? = degree of dissociation = 0.6
Total number of moles at equilibrium(observed moles) = 1 - \alpha? +  \alpha? +  \alpha? 

= 1+ \alpha = 1.6

 Total number of moles at equilibrium(theoretical moles) = initial moles

= 1 + 0 + 0 = 1  

Theoretical molar mass = molar mass of PCl5 = 208.5

Now. from mass conservation we have

Theoretical moles X Theoretical molar mass = Observed moles X Observed molar mass

\Rightarrow\mathrm{1 \times 208.5 = 1.6 \times M_{obs}}?

\therefore \mathrm{M_{obs} = \frac{208.5}{1.6}=130.3}?

Therefore, option(1) is correct

Posted by

SANGALDEEP SINGH

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