Q. A mixture of `NaCl` and `NaI` when heated with `H_2SO_4` , produced the same weight of sodium sulphate as that of the original mixture.Calculate percentage of `NaI` in the mixture.
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Let, the total amount of mixture of NaCl and NaI taken initially was x g, out of which amount of NaCl was y g. So, amount of NaI in the initial mixture was (x-y) g.
Balanced chemical reactions of NaCl and NaI with H2SO4 are as follows:
2NaCl + H2SO4 -> Na2SO4 + HCl
2NaI + H2SO4 -> Na2SO4 + HI
Amount of components obtainable/reacting freom stoichiometric considerations are as follows:
NaCl Na2SO4 NaI Na2SO4
------ --------- ---------- ------------
117 142 300 142
`y` `(142*y)/117` `(x-y) ` `(142*(x-y))/300`
By condition, `(142*y)/117+(142*(x-y))/300 = x` ` `
`rArr 14200y+5538x-5538y=11700x ` (LCM of 117 and 300 is 11700)
This is the percent (by mass) of NaCl present in the original mixture.
Therefore, percent (by mass) of NaI present in the original mixture was 100-71.14=28.86.
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