Using ΔTb=Kb×Mw×W1000
For PQ: 1.176=5×MPQ1×501000=MPQ100
MPQ=1.176100=85 g/mol
For PQ2: 0.689=MPQ2100
MPQ2=0.689100=145 g/mol
P+Q=85 ... (i)
P+2Q=145 ... (ii)
Subtracting: Q=60 g/mol
From (i): P=85−60=25 g/mol
JEE Main 2026 — Chemistry Physical Chemistry
Elements P and Q form two types of non-volatile, non-ionizable compounds PQ and PQ2. When 1 g of PQ is dissolved in 50 g of solvent ′A′,ΔTb was 1.176 K while when 1 g of PQ2 is dissolved in 50 g of solvent ′A′,ΔTb was 0.689 K. (Kb of ' A′=5 K kg mol−1). The molar masses of elements P and Q (in gmol−1) respectively, are :
Held on 21 Jan 2026 · Verified 6 Jul 2026.
70,110
65,145
25,60
60,25
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