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?

1 Answer
Oct 2, 2017

Answer:

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%#