The density of 3M solution of Na2S2O3 is 1.25gmL−1. Calculate, the molalities of Na+ and S2O2−3 ions respectively.
A
7.732 and 3.865
Right on! Give the BNAT exam to get a 100% scholarship for BYJUS courses
B
3.865 and 7.732
No worries! We‘ve got your back. Try BYJU‘S free classes today!
C
5.643 and 4.321
No worries! We‘ve got your back. Try BYJU‘S free classes today!
D
None of the above
No worries! We‘ve got your back. Try BYJU‘S free classes today!
Open in App
Solution
The correct option is A 7.732 and 3.865 Given, Molarity of Na2S2O3=3molL−1 ∴ Moles of Na2S2O3=3 ∴Weight of Na2S2O3=3×158=474g and Volume of solution =1L=1000mL ∴Weight of solution =1000×1.25=1250g ∴Weight of water=1250−474=776g
Molality of Na+=Moles ofNa+Weight of water (g)×1000=6×1000776=7.732
Molality of S2O2−3=3×1000776=3.865