Calculate the mass in grams of hydrogen chloride produced when 5.15 l of molecular hydrogen measured at stp reacts with an excess of molecular chlorine gas. h2 (g) + cl2 (g) → 2hcl (g)

Answer: 17.9 g

Explanation:

1) Chemical equation:

H₂ (g) + Cl₂ (g) → 2HCl (g)

2) mole ratios:

1 mol H₂ : 1 mol Cl₂ : 2 mol HCl

3) Since, the pressure and temperature conditions do not change, the same proportion is valid for the volumes. Then:

1 liter H₂ / 2 liter HCl = 5.15 liter H₂ / x

⇒ x = 5.5 * 2 / 1 = 11 liter HCl

4) Calculate the number of moles of HCl in 11 liter of HCl at STP

At STP, 1 mol of gas = 22.4 liter

⇒ 11 liter * 1mol / 22.4 liter = 0.491 mol HCl

5) Use the molar mass to convert 0.491 mol to grams

molar mass of HCl = 1.008 g/mol + 35.453 g/mol = 36.461 g/mol

mass in grams = nuumber of moles * molar mass = 36.461 g/mol * 0.491 mol = 17.90 g.