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JEE Advanced2022ChemistrySome Basic Concepts of ChemistryActual

To check the principle of multiple proportions, a series of pure binary compounds P m Q n were analysed and their composition is tabulated below. The correct option(s) is(are) Compound Weight % of P Weight % of Q 1 50 50 2 44 . 4 55 . 6 3 40 60

Options

  1. AIf empirical formula of compound 3 is P 3 Q 4 , then the empirical formula of compound 2 is P 3 Q 5 .
  2. BIf empirical formula of compound 3 is P 3 Q 2 and atomic weight of element P is 20 , then the atomic weight of
  3. CIf empirical formula of compound 2 is PQ , then the empirical formula of the compound 1 is P 5 Q 4 .
  4. DIf atomic weight of P and Q are 70 and 35 , respectively, then the empirical formula of compound 1 is P 2 Q .

Correct answer

B. If empirical formula of compound 3 is P 3 Q 2 and atomic weight of element P is 20 , then the atomic weight of

Step-by-step solution

(A) If empirical formula of 3 is P 3 Q 4 , then molecular formula is P 3 Q 4 n ⇒    3 M P 3 M P + 4 M Q = 40 100 = 2 5 15 M p = 6 M p + 8 M Q 9 M P = 8 M Q ∴ For P 3 Q 5 , % of P = 3 M P 3 M P + 5 M Q × 100 = 8 M Q 23 M Q × 100 = 34 . 78 % (B) If empirical formula of compound 3 is P 3 Q 2 , we have 3 M P 3 M P + 2 M Q = 2 5 15 M P = 6 M P + 4 M Q 9 Mp = 4 M Q If M p = 20 M Q = 180 4 = 45 (C) If empirical formula of 2 is PQ ∴    M P M P + M Q = 4 9 = 44 . 44 100 9 Mp =

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