Thirty grams of lead oxide and fifteen grams of ammonia react completely to produce solid lead, nitrogen gas, and liquid water. What will be approximate mass of all three products?

Expert Answers
gsenviro eNotes educator| Certified Educator

The balanced chemical equation for this reaction is given as:

`3 PbO + 2 NH_3 -> 3 Pb + N_2 + 3 H_2O`

Thus, 3 moles of lead oxide react with 2 moles of ammonia to generate 3 moles of lead, 1 mole of nitrogen gas and 3 moles of water. 

Molar mass of lead oxide = 207.2 + 16 = 223.2 gm/mole

Molar mass of ammonia = 14 + 3 x 1 = 17 gm/mole

Molar mass of lead = 207.2 gm/mole

Molar mass of nitrogen gas = 28 gm/mole

Molar mass of water = 18 gm/mole

Given moles of lead oxide = 30/223.2 = 0.1344 moles

Moles of ammonia = 15/17 moles = 0.8824 moles.

Since, 3 moles of PbO reacts with 2 moles ammonia, 0.1344 moles will react with 2/3 x 0.1344 = 0.0896 moles or say 0.09 moles.

Thus, PbO is in limiting quantity.

Using the given chemical reaction:

3 moles of PbO generate 3 moles of lead. Thus, 0.1344 moles of Pb or 27.85 gm (= 0.1344 x 207.2) Pb will be produced.

Similarly, 3 moles of PbO produce 1 mole of nitrogen gas. Thus, 0.0448 moles (= 1/3 x 0.1344) or 1.2544 gm (or 1.25 gm) nitrogen gas will be generated.

Similarly, 0.1344 moles or 2.42 gm (=0.1344 x 18) water will be generated.

Hope this helps.