Question

In the mixture of NaHCO3 ​ and Na 2 ​ CO 3 ​ , volume of a given HCl required is x ml with phenolphthalein indicator and further y ml is required with methyl orange indicator. the moles co2 evolved on heating the above mixture at lower temperature is

Answer 1

Answer:

i. With phenolphthalein indicator, NaHCO

3

does not react with HCl whereas with Na

2

CO

3

is 50% reaction.

V

HCl

=x mL (Half titre value of Na

2

CO

3

)

ii. With methyl orange indicator, NaHCO

3

reacts completely with HCl and with Na

2

CO

3

is 100% reaction.

But y mL of HCl is added after Na

2

CO

3

has reacted upto NaHCO

3

i.e., half titre value of Na

2

CO

3

.

V

HCl

=Full litre value of NaHCO

3

+ Half titre value of Na

2

CO

3

y mL=x

′

+x mL

∴ Volume of HCl required for complete reaction of Na

2

CO

3

=x mL+x mL=2x mL