Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g) From the equation above, the mass of magnesium...

JAMB 1999

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

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Correct Answer: Option B

Explanation

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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