JEE Main 2019 — Some Basic Concepts Of Chemistry Question with Solution
From: JEE Main 2019 (Online) 12th April Morning Slot
Question
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:
Choose an option
Show full solutionCorrect option: C
Correct answer
CMA = 5 × 10–3
and MB = 10 × 10–3
Step-by-step 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
AB2 = 25 g/mol
10 mol A2B2 weighs 300 g
A2B2 = 30 g/mol
So, MA + 2MB = 25 ..............(1)
and 2(MA + MB) = 30 ..............(2)
By solving (1) and (2),
MA = 5 gm = 5 10-3 kg
MB = 10 gm = 10 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
AB2 = 25 g/mol
10 mol A2B2 weighs 300 g
A2B2 = 30 g/mol
So, MA + 2MB = 25 ..............(1)
and 2(MA + MB) = 30 ..............(2)
By solving (1) and (2),
MA = 5 gm = 5 10-3 kg
MB = 10 gm = 10 10-3 kg
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This is a previous-year question from JEE Main 2019, covering the Some Basic Concepts Of Chemistry chapter of Chemistry. PrepSharp catalogues every PYQ from JEE Main with a verified answer key and step-by-step solution prepared by IIT alumni — so you can search by chapter, topic or year and revise efficiently.