Question

Calculate the volume of hydrogen produced at s.t.p, when (25g)of zinc are added to exess dilute hydrochloric acid 30°c and 778mmhg pressure (H=1,Zn=65,Cl=35.5, molar volume of a gas at s.t.p=22.4dm³

Answer 1

Zn + 2HCL = ZnCl2 + H2

Moles of Zn = Mass/Molar Mass

           Moles = 25/65

                       = 0.385 moles

Moles of H2 = 0.385 moles since the mole ratio is 1:1

But moles of H2 at stp = vol/Molar gas volume

           Therefore vol = moles x Molar gas volume

                       Vol = 0.385 x 22.4

                       Vol = 8.615 dm³