As a result of the treatment of brass (an alloy of copper and zinc) weighing 10 g with an excess of hydrochloric acid

As a result of the treatment of brass (an alloy of copper and zinc) weighing 10 g with an excess of hydrochloric acid, a gas of 1.12 dm2 was released. Set the composition of the alloy in mass fractions.

1.Only one component of the alloy, zinc, will interact with hydrochloric acid, since copper in the electrochemical series is located after hydrogen and is not able to displace it from acid solutions:

Zn + 2HCl = ZnCl2 + H2 ↑;

2. Let’s calculate the chemical amount of released hydrogen:

n (H2) = V (H2): Vm = 1.12: 22.4 = 0.05 mol;

3. Determine the amount and mass of zinc:

n (Zn) = n (H2) = 0.05 mol;

m (Zn) = n (Zn) * M (Zn) = 0.05 * 65 = 3.25 g;

4. Find the mass of copper in the alloy:

m (Cu) = m (brass) – m (Zn) = 10 – 3.25 = 6.75 g;

5. Let’s establish the mass fractions of metals in the alloy:

w (Zn) = m (Zn): m (brass) = 3.25: 10 = 0.325 or 32.5%;

w (Cu) = m (Cu): m (brass) = 6.75: 10 = 0.675 or 67.5%.

Answer: 32.5% Zn and 67.5% Cu.