Question

5 moles of AB2 weigh 125×10−3kg and 10 moles of A2B2 weigh 300×10−3kg.The molar mass of A(MA) and molar mass of B(MB) in kg/mol are :

• A. $M_A=10\times {10}^{-3}and{M}_B=5\times {10}^{-3}$
• B. $M_A=25\times {10}^{-3}and{M}_B=50\times {10}^{-3}$
• C. $M_A=5\times {10}^{-3}and{M}_B=10\times {10}^{-3}$
• D. $M_A=50\times {10}^{-3}and{M}_B=25\times {10}^{-3}$

Answer 1

The correct option is C MA=5×10−3andMB=10×10−3
Number of moles=Given massMolar mass
For AB2
5=125MA+2MB
MA+2MB=25..........(1)
For A2B2
10=3002MA+2MB
2MA+2MB=30..........(2)
Solving 1 and 2 ;
MA=5g/mol=5×10−3kg/mol
MB=10g/mol=10×10−3kg/mol