A mixture contains only NaCl and Al2(SO4)3. A 1.75-g sample of the mixture is dissolved in water, and an excess of NaOH is added, producing a precipitate of Al(OH)3. The precipitate is filtered, dried, and weighed. The mass of the precipitate is 0.134 g. What is the mass percent of Al2(SO4)3 in the sample?
It is given precipitate = Al(OH)3
Mass of precipitate, Al(OH)3 = 0.134 g
moles of precipitate formed =
Al2(SO4)3 + 6 NaOH --> 2 Al(OH)3 & 3 Na2SO4
From the question it is clear that for the mixture of Al2(SO4)3 & NaCl, the reaction shows that NaOH reacts with Al2(SO4)3 to form Al(OH)3
Mass of Al2(SO4)3 required =
Mass of Al2(SO4)3 required to produce 0.134 g Al(OH)3 = 0.294 g Al2(SO4)3
Mass percentage of Al2(SO4)3 is =
% mass of Al2(SO4)3 = 16.8
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