moles of SO
2 =
22400224 = 0.01
moles of NaOH = molarity × volume (in litre)
= 0.1 × 0.1
= 0.01 moles
The balanced equation is
SO
2 + 2NaOH
Na
2SO
3 + H
2O
Here NaOH is limiting Reagent.
2 mole NaOH produces 1 mole Na
2SO
3
0.01 mole NaOH produces
0.01 mole Na
2SO
3
Moles of Na
2SO
3 = 0.005 mole
Na
2SO
3 2Na
+ + SO
32-
van’t Hoff factor (i) = 3
Moles of H
2O =
1836 = 2 moles
Accoding to Relative Lowering of Vapour :
PH2OoPH2Oo−PS=nH2O+inNa2CO3inNa2CO3
[
nNa2CO3 <<
]
PH2OoPH2Oo−PS=nH2OinNa2CO3
2424−PS=23×0.005
24 – P
S = 0.18
P
S = 23.82
Lowering in pressure (
P) = 0.18 mm of Hg
= 18 × 10
–2 mm of Hg