Question

A mixure of 1.65 × 10^21 molecules of x and 1.85 × 10^21 molecules of y weighs 0.688 g. The mol. Wt. Of x is (assume mol. Wt. Of y is 187)

Answer 1

n₁ = 1.85×10²¹÷ 6.023×10²³

= 0.003 moles

n= m/M.wt.

0.003 = m/187

m= 0.561 g

mass of x + mass of y = 0.688

mx + 0.561 = 0.688

mx = 0.127 g

n₂ = 1.65×10²¹÷6.023×10²³

n₂ = 0.0028 moles

n₂ = mx/ M.wt

0.0028 = 0.127/M.wt

M.wt = 0.127/0.0028

M.wt. = 47 g/mol.