Question

Samples of compounds are decomposed and the masses of their constituent elements are shown below. Calculate the empirical formula for each compound.

0.381 g Al, 5.381 g I

2.677 g Ba, 1.382 g Cl

2.128 g Be, 7.557 g S, 15.107 g O

Answer 1

1) 0.381 g Al, 5.381 g I

Al moles = 0.381 / 27 = 0.014

I moles = 5.381 / 127 = 0.0424

Al : I = 0.014 : 0.0424 = 1:3

empirical formula = Al I3

2.677 g Ba, 1.382 g Cl

Ba moles = 2.677 / 137 = 0.0195

Cl moles = 1.382 / 35.5 = 0.0389

Ba : Cl = 1:2

empirical formula = BaCl2

2.128 g Be, 7.557 g S, 15.107 g O

Be moles = 2.128 / 9 = 0.236

S moles = 7.557 / 32 = 0.236

O moles = 15.107 / 16 = 0.944

Be : S : O   = 1 : 1 : 4

empirical formula   BeSO4