Question

At.298k v.p of pure cs2 is 845 torr. A solution of 2g of sulphur in 100 gm of cs2 has v.p of 848.9 torr

Answer 1

According to Rault's law
P∘−PSPS=w/mW/M
P
∘
-
P
S
P
S
=
w
/
m
W
/
M

Given, P∘=854torr,PS=848.9torr,w=2.0g
P
∘
=
854
torr
,
P
S
=
848.9
torr
,
w
=
2.0
g
,
m=?,W=100,M=76(forCS2)
m
=
?
,
W
=
100
,
M
=
76
(
for
C
S
2
)

∴854−848.9848.9=2.0×76100×m
∴
854
-
848.9
848.9
=
2.0
×
76
100
×
m

⇒m=253
⇒
m
=
253

Now, the formula of sulphur =Sn
=
S
n

∵n×32=253
∵
n
×
32
=
253

∴n=7.9≈8