Jawaban:

Diket:

massa X = 31 gram

massa air = 171 gram

Mr air = 18

P = 28,5 mmHg

Po = 30 mmHg

Kb = 0,52 'C/m

Dit:

a. Mr X.....?

b. Tb larutan...?

jawab:

P = Po . Xa

Xa = P/Po

Xa = 28,5/30

Xa = 0,95

,

\begin{gathered} X_{a} = \frac{ n_{a} }{ n_{a}+ n_{X} } \\ \\ 0,95= \frac{ \frac{171}{18} }{ \frac{171}{18}+ \frac{31}{Mr} } \\ \\ 0,95= \frac{9,5}{9,5+ \frac{31}{Mr} } \\ \\ 0,95(9,5+ \frac{31}{Mr} )=9,5 \\ \\ 9,5+ \frac{31}{Mr} = \frac{9,5}{0,95} \\ \\ \frac{31}{Mr} =10-9,5 \\ \\ Mr= \frac{31}{0,5} \\ \\ Mr=62\end{gathered}

X

a

=

n

a

+n

X

n

a

0,95=

18

171

+

Mr

31

18

171

0,95=

9,5+

Mr

31

9,5

0,95(9,5+

Mr

31

)=9,5

9,5+

Mr

31

=

0,95

9,5

Mr

31

=10−9,5

Mr=

0,5

31

Mr=62

b. ΔTb = Kb . m

ΔTb = kb . (m/Mr x 1000/p)

ΔTb = 0,52 (31/62 x 1000/171)

ΔTb = 0,52 (0,5 x 5,8)

ΔTb = 1,5'C

.

Tb larutan = Tb pelarut + ΔTb

Tb larutan = 100 + 1,5

Tb larutan = 101,5 'C

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