Question

The empirical formula for a compound that contains 3.91 grams aluminum and 3.49 grams oxygen is:A)Al2O3B)Al3O2C)AlO2D)Al2O

Answer 1

Answer : Option C , ALO2

1. calculate number of moles for Aluminimun ;

given that mass = 3.91 g

Molecular mass =26,98

∴ moles = 3.91 g/26.98

= 0.144 moles

2. Calculate number of moles for Oxygen

given that mass = 3.49 g

Molecular mass =16g/mol

∴ moles = 3.49g/16g/mol

=0.218 moles

3. Divide all components by the smallest value:

• Aluminium : 0.144 /0.144 moles= ,1 mole

,

• Oxygen : 0.218 /0.144 =1.5 moles≈ ,2 moles

Therefore the emperical formula is AlO2