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 0.3g
  • B 1.5g
  • C 2.4g
  • D 3.0g
jamb 1999chemistry

The correct answer is B. 1.5g

Molar conc. =no.of moles／Vol in dm3

Vol=250cm3= 0.25dm3

Molar conc=0.5M

No of moles=molar conc *Vol in dm3

=0.5*0.25

=0.125mole of HCl

2moles of HCl → １Mole of Mg

0.125 mole →(0.125*1)/2

=0.0625mole of Mg

Reacting mass=no of moles* molar mass

Mg=24

Mass=0.0625*24

=1.5g

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