A) A = 25.59 u, B = 42.64 u
B) A = 36.78 u, B = 49.38 u
C) A = 42.64 u, B = 25.59 u
D) A = 49.38 u, B = 36.78 u
Correct Answer: A
Solution :
\[{{M}_{2}}=\frac{1000\,{{K}_{f}}{{w}_{2}}}{{{w}_{1}}\times \Delta {{T}_{f}}}\] \[{{M}_{A{{B}_{2}}}}=\frac{1000\times 5.1\times 1}{20\times 2.3}=110.87\,g\,mo{{l}^{-1}}\] \[{{M}_{A{{B}_{4}}}}=\frac{1000\times 5.1\times 1}{20\times 1.3}=196.15\,g\,mo{{l}^{-1}}\] Suppose atomic masses of A and B are a and b respectively. Then Molar mass of \[A{{B}_{2}}=a+2b=110.87g\,mo{{l}^{-1}}\] ...(i) Molar mass of \[A{{B}_{4}}=a+4b=196.15\,g\,mo{{l}^{-1}}\] ...(ii) On subtracting Eq (i) from (ii) 2b = 85.28 or b = 42.64 On substituting value of b in Eq. (i) \[a+2\times 42.64=110.87\] \[a=25.59\] Atomic mass of A = 25.59 u Atomic mass of B = 42.64 uYou need to login to perform this action.
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