Question

A sample of indium chloride, `"InCl"_3`, is known to be contaminated with sodium chloride, NaCl. The contaminated sample is then treated with excess `"AgNO"_3`(aq). What is the percentage by mass of `"InCl"_3` in the sample?

A sample of indium chloride, `"InCl"_3`, is known to be contaminated with sodium chloride, NaCl. The contaminated sample weighs 2.55 g. When the contaminated sample is treated with excess `"AgNO"_3`(aq), 5.16 grams of AgCl(s) are obtained. What is the percentage by mass of `"InCl"_3` in the sample?

Answer 1

Purity of `InCl_3` is about `84.4%`.

Explanation:

First, write down chemical equation and see what happens:

`InCl_3 + 3 AgNO_3 -> In(NO_3)_3 + 3AgCl`
`NaCl + AgNO_3 -> NaNO_3 + AgCl`

Atomic weights for `N, O, Cl, Na, Ag` and `In` are `14.0, 16.0, 35.5, 23.0, 107.9` and `114.8`, respectively.
Then calculate the molar mass(g/mol).
`InCl_3 = 221.3`, `NaCl=58.5` and `AgCl=143.4`

Now let `x` to be amount of `InCl_3` in mole, and y to be that of `NaCl`.

Consider the weight of sample:
`221.3x+58.5y=2.55` ・・・(1)
Consider the weight of `AgCl`:
`143.4(3x+y)=5.16`・・・(2)

Solve the simultaneous equation and you will find:
`x=9.72xx10^(-3) "moles" and y=6.84xx10^(-3) "moles"`

The amount of `InCl_3` is `221.3xx9.72xx10^(-3)=2.15` grams, and the percentage in mass of `InCl_3` is `2.15/2.55xx100=84.4%`