Elements P and Q form two types of non-volatile, non-ionizable compounds PQ and PQ _ 2 . When 1 g of PQ is dissolved in 50 g of solvent ^ A ^ , T _ b was 1.176 K while when 1 g of PQ _ 2 is dissolved in 50 g of solvent ^ A ^ , T _ b was 0.689 K. ( K _ b of ' A ^ =5 ~K ~kg ~mol ^ -1 ). The molar mass

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Elements P and Q form two types of non-volatile, non-ionizable compounds PQ and PQ _ 2 . When 1 g of PQ is dissolved in 50 g of solvent ^ A ^ , T _ b was 1.176 K while when 1 g of PQ _ 2 is dissolved in 50 g of solvent ^ A ^ , T _ b was 0.689 K. ( K _ b of ' A ^ =5 ~K ~kg ~mol ^ -1 ). The molar masses of elements P and Q (in g mol ^ -1 ) respectively, are :

Quantrex Academy · Accepted Answer

Correct answer: C. 25,60

Using T_b = K_b w M 1000 W For PQ: 1.176 = 5 1 M_ PQ 1000 50 = 100 M_ PQ M_ PQ = 100 1.176 = 85 g/mol For PQ_2: 0.689 = 100 M_ PQ_2 M_ PQ_2 = 100 0.689 = 145 g/mol P + Q = 85 ... (i) P + 2Q = 145 ... (ii) Subtracting: Q = 60 g/mol From (i): P = 85 - 60 = 25 g/mol

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