Question

A.) If 3.0 grams of nitrogen reacts with 2.0 grams of hydrogen to form ammonia (NH3), how many grams of excess reactant remain after the reaction has run to completion?

B.) In the combustion analysis of ferrocene (molar mass = 186.0 g/mol), which contains only Fe, C, and H, a 0.9437g sample produced 2.233g of CO2 and 0.457g of H20. What are the empirical and molecular formulas of ferrocene?

Answer 1

A) N2(g) + 3H2(g) ---- 2NH3(g)

Number of moles of N2 = 3/28 = 0.10714 moles

Number of moles of H2 = 2/2 = 1 mole

Hence N2 is the limiting reagent in the reaction

1 mole of N2 reats with 3 mole of H2

Moles of H2 left = 1 - 0.10714 * 3 = 0.6785 moles

Mass of H2 left = 0.6785 moles * 2 gm/mol = 1.357 grams

B)

Number of moles of CO2 = 2.233/44 = 0.05075 moles

Number of moles of Ferrocene = 0.9437/186 = 0.005073 moles

Hence 1 mole of ferrocene gives 10 moles of CO2

Therefore 1 mole of ferrocene will contain 10 moles of carbon atom

Number of moles of H2O = 0.457/18 = 0.2538 moles

1 mole of H2O will contain two moles of hydrogen atoms, hence number of hydrogen atoms are 10

Let the formula be C10H10Fex

10*12 + 10*1 + 56* x= 186

x = 1

Hence the empirical amd molecular formula both are C10H10Fe