Question

Combustion of a 0.9827-g sample of a compound containing only carbon, hydrogen, and oxygen produced 1.900 g of CO2 and 1.070 g of H2O. What is the empirical formula of the compound?   

Of the choices below, which would be the best for the lining of a tank intended for use in storage of hydrochloric acid? Explain your reasoning.                                                   (2)

A) copper

B) zinc

C) nickel

D) iron

E) tin

Answer 1

Ans 1

Mass of sample = 0.9827 g

Moles of H2O = mass/molecular weight

= ( 1.070 g) / (18.03 g/mol)

= 0.05935 mol

Moles of CO2 = mass/molecular weight

= ( 1.900 g) / (44.01 g/mol)

= 0.04317 mol

Mass of O2 = (1.900 + 1.070) - (0.9827)

= 1.9873 g

Moles of O2 = (1.9873 g) / (32 g/mol)

= 0.06210 mol

Moles of C = 0.04317 mol

Moles of H = 2 x 0.05935 = 0.1187 mol

Moles of O = 0.05935 + 2 x 0.04317 - 2 x 0.06210

= 0.02149 mol

Molar ratio of C : H : O = 0.04317 : 0.1187 : 0.02149

Divide by 0.02149

Molar ratio of C : H : O = 2 : 5.5 : 1

Multiply by 2

Molar ratio of C : H : O = 4 : 11 : 2

Empirical formula of the compound = C₄H₁₁O₂