Verified Solution • 2025–26 Session
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QJEEM19Ch79ad: JEE Main 2019 Chemistry - Class 11 JEEM19Ch79ad Solution: 5 moles of AB 2 weigh 125 × 10 –3 kg and 10 moles of A 2 B 2…
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:
Multiple Choice Options
- A MA = 10 × 10–3 and MB = 5 × 10–3
- B MA = 25 × 10–3 and MB = 50 × 10–3
- C MA = 5 × 10–3 and MB = 10 × 10–3
- D MA = 50 × 10–3 and MB = 25 × 10–3
Step-by-Step Verified Solution
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
10 mol A2B2 weighs 300 g
So, MA + 2MB = 25 ..............(1)
and 2(MA + MB) = 30 ..............(2)
By solving (1) and (2),
MA = 5 gm = 5
MB = 10 gm = 10
Molar weigh of 'B' = MB
Molar mass of AB2 = MA + 2MB
Molar mass of A2B2 = 2(MA + MB)
5 mol AB2 weighs 125 g
10 mol A2B2 weighs 300 g
So, MA + 2MB = 25 ..............(1)
and 2(MA + MB) = 30 ..............(2)
By solving (1) and (2),
MA = 5 gm = 5
MB = 10 gm = 10