A gas sample contains 16.0 g of CH4, 16.0 g of O2, 16.0 g of SO2, and 33.0 g of CO2. What is the total number of moles of gas in the sample?:

A) 2.50 moles

B) 3.00 moles

C) 2.75 moles

D) 2.25 moles

E) 4.00 moles

The answer is A) 2.50 moles

Atomic masses (A) of the following atoms are:

A (C) = 12 g/mol

A (O) = 16 g/mol

A (H) = 1 g/mol

A (S) = 32 g/mol

The number of moles (n) is the quotient of mass (m) and molar mass (M)

n = m/M

m (CH4) = 16.0 g

M (CH4) = A (C) + 4A (H) = 12 + 4 * 1 = 12 + 4 = 16 g/mol

n (CH4) = 16.0 g / 16 g/mol = 1 mol

m (O2) = 16.0 g

M (O2) = 2A (O) = 2 * 16 = 32 g/mol

n (O2) = 16.0 g / 32 g/mol = 0.5 mol

m (SO2) = 16.0 g

M (SO2) = A (S) + 2A (O) = 32 + 2 * 16 = 32 + 32 = 64 g/mol

n (SO2) = 16.0 g / 64 g/mol = 0.25 mol

m (CO2) = 33.0 g

M (CO2) = A (C) + 2A (O) = 12 + 2 * 16 = 12 + 32 = 44 g/mol

n (CO2) = 33.0 g / 44 g/mol = 0.75 mol

The total number of moles of gas in the sample is:

n (CH4) + n (O2) + n (SO2) + n (CO2) = 1 mol + 0.5 mol + 0.25 mol + 0.75 mol =

= 2.50 moles