Answer to Question #287172 in Organic Chemistry for buddy

Question

 When 9.0 g of hydrogen gas, H₂, reacts with oxygen gas, O₂, 73.0 g of water is produced.    2H2 + O2 --> 2H2O a) What is the theoretical yield of water? b) What is the percentage yield?

2. Powdered zinc metal reacts with sulphur (S₈) when heated to produce zinc sulphide.

a) What mass of product can be produced with 25 g of zinc?

b) What is the actual yield if the percentage yield was 80%?

3. The thermite reaction has been used to weld railroad rails, make bombs, and ignite solid rocket fuel. The equation of the reaction is:

a) What is the theoretical yield of iron if 100.0 g of Fe₂O₃ is used?

b) What is the percentage yield if 52.3 g of iron is actually produced?

Answer 1

The equation for this reaction is

2H₂ + O₂ = 2H₂O;

Having a mass of hydrogen we can find the quantity substance

n(H₂) = m(H₂)/M(H₂);

M(H₂) = 1 *2 = 2 g/mol

n(H₂) = 9 g / 2 g/mol = 4.5 moles;

The amount of substance of hydrogen with the amount of substance of water as

a 2 to 2 or 1 to 1.

so n(H₂O) = 4.5 moles

Theoretical mass of water will be

n(H₂O) = m(H₂O)/M(H₂O);

M(H₂O) = 1 *2 + 16 = 18 g/mol

m (H₂O) 4.5 moles * 18 g/mol = 81 g.

so the theoretical yield of water is 81 g.

The percentage yield will be

m(H₂O)practical / m(H₂O)theoretical = 73.0 g / 81.0 g = 0.9012 or 90.12 %