The density of 3M sodium thiosulphate is `1.25g//mL`, identify the correct statements among the following:

Options

A. % by weight of sodium thiosulphate is `37.92`
B. The mole fraction of sodium thiosulphate is `0.065`
C. The molarity of `Na^(+)` is `2.53` and `S_(2)O_(3)^(2-)` is 1.25
D. All of these

Answer

A, B

Explanation

`M = (% by Wt xx 10 xx d)/(M.Wt)` [M.Wt of `Na_(2)S_(2)O_(3) = 46 +64 +48 = 158]`
`3 = (% by Wt xx 10 xx 1.25)/(M.Wt)`
% by Wt `=(3 xx 158)/(12.5) = (474)/(12.5) = 37.92`
`m = (M xx 1000)/(1000 xx d - M xx M.Wt) = (3 xx 1000)/(1000 xx 1.25 - 3xx 158)`
`= (3000)/(1250 - 474) = (3000)/(776) = 3.86`
(B) is correct because
`X_(B) = (3.86)/(3.86+(1000)/(18)) = (3.86)/(3.86 +55.80) = (3.86)/(59.36) = 0.065`