Consider the reaction of zn metal with hydrochloric acid: zn (s) + 2hcl (aq) → zncl2 (aq) + h2 (g) if 7.50 g of zn is reacted with 0.225 moles of hcl in a 2.00 l container what pressure does the generated h2 exert against the container walls at 25.8 ℃?

The balanced equation for the reaction is as follows;

Zn + 2HCl - - > ZnCl₂ + H₂

we need to first find which is the limiting reactant

stoichiometry of Zn to HCl is 1:2

number of Zn moles - 7.50 g / 65.4 g/mol = 0.115 mol

number of HCl moles - 0.225 mol

if Zn is the limiting reactant

according to molar ratio 1:2

amount of 0.115 mol of Zn should react with - 2 x 0.115 = 0.23 mol

but only 0.225 mol of HCl present therefore HCl is the limiting reactant

amount of products formed depends on amount of HCl present

stoichiometry of HCl to H₂ is 2:1

number of H₂ moles formed - 0.225 / 2 = 0.113 mol

we can use the ideal gas law equation to find the pressure exerted

PV = nRT

where

P - pressure

V - volume - 2.00 x 10⁻³ m³

n - number of moles - 0.113 mol

R - universal gas constant - 8.314 Jmol⁻¹K⁻¹

T - temperature - 25.8 °C + 273 = 298.8 K

substituting these values in the equation

P x 2.00 x 10⁻³ m³ = 0.113 mol x 8.314 Jmol⁻¹K⁻¹ x 298.8 K

P = 140.4 kPa