JEE MAIN - Chemistry (2019 - 12th April Morning Slot - No. 4)
5 moles of AB2 weigh 125 × 10–3
kg and 10 moles of A2B2 weigh 300 × 10–3
kg. The molar mass of A (MA)
and molar mass of B (MB) in kg mol are:
MA = 10 × 10–3
and MB = 5 × 10–3
MA = 25 × 10–3
and MB = 50 × 10–3
MA = 5 × 10–3
and MB = 10 × 10–3
MA = 50 × 10–3
and MB = 25 × 10–3
Explanation
Molar weigh of 'A' = MA
Molar weigh of 'B' = MB
Molar mass of AB2 = MA + 2MB
Molar mass of A2B2 = 2(MA + MB)
5 mol AB2 weighs 125 g
$$ \therefore $$ AB2 = 25 g/mol
10 mol A2B2 weighs 300 g
$$ \therefore $$ A2B2 = 30 g/mol
So, MA + 2MB = 25 ..............(1)
and 2(MA + MB) = 30 ..............(2)
By solving (1) and (2),
MA = 5 gm = 5 $$ \times $$ 10-3 kg
MB = 10 gm = 10 $$ \times $$ 10-3 kg
Molar weigh of 'B' = MB
Molar mass of AB2 = MA + 2MB
Molar mass of A2B2 = 2(MA + MB)
5 mol AB2 weighs 125 g
$$ \therefore $$ AB2 = 25 g/mol
10 mol A2B2 weighs 300 g
$$ \therefore $$ A2B2 = 30 g/mol
So, MA + 2MB = 25 ..............(1)
and 2(MA + MB) = 30 ..............(2)
By solving (1) and (2),
MA = 5 gm = 5 $$ \times $$ 10-3 kg
MB = 10 gm = 10 $$ \times $$ 10-3 kg
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