Question

What is the % error if the experiment of H2O in Alum is 42.34%?

Answer 1

Experimental H₂O in Alum is 42.34% (given)

Calculate theoretical H₂O in Alum

Calculate molar mass of alum (KAl(SO₄)₂.12H₂O)

39.098 + 26.982 + 2(32.06) + 20 (15.999) + 24(1.0079) = 474.3696 g/mol

There are 12 molecules of water in alum

Molar mass H₂O = (15.999) + 2(1.0079) = 18.0148

There are 12 molecules of water in alum

Mass of water in alum = 18.0148*12 = 216.1776

% H₂O = (216.1776/474.3696)*100 = 45.57%

% error = [(Experimental – theoretical) / theoretical] x 100

              = [(42.34 – 45.57)/45.57] x 100 = 7.08 %