Which of the following gases will diffuse fastest when passed through a porous plug?
[H = 1, C = 12, N = 14, O = 16]

Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
From the equation above, the mass of magnesium required to react with 250cm3 of 0.5M HCl is
[Mg = 24]

A gaseous metallic chloride MClx consists of 20.22% of M by mass. The formula of the chloride is?
[M = 27, Cl = 35.5]