25 ml of H2 and 18ml of I2 vapours were heated in a sealed vessel at 456 C when at equilibrium 30.8 ml of HI was formed. Calculate the degree of dissociation of pure HI

Dear student,

The degree of dissociation of HI can be calculated from the reaction,

H2 +I22HI
Clearly, I2 is the limiting reagent hence the amount of HI formed depends on volume of I2 .
1 mL of I2 will produce 2 mL of HI, hence 18mL of I2 will produce 36 mL HI theoretically.
Volume of HI formed theoretically = 36 mL
​Volume of HI formed actually = 30.8 mL

Degree of dissociation = 30.836×100 = 85.55%
Hope this helps,


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