JAMB - Chemistry (1986 - No. 36)
What mass of a divalent metal M (atomic mass = 40) would react with excess hydrochloric acid to liberate 224cm^3 dry hydrogen gas measured at S.T.P?
8.0 g
4.0 g
0.8 g
0.4 g
설명
let the divalent metal be Q
Q + 2HCl → QCl2 + H2
1mole of Q liberated 1 mole of Hydrogen gas ( one mole of any gas at STP has a volume of 22400cm^3 or 22.4dm^3 )
40 → 22400cm^3
? → 224cm^3
mass of Q = \(\frac{ 40 \times 224}{22400}\)
mass of Q = 0.4g.