1

### NEET 2016 Phase 2

Which one of the following is incorrect for ideal solution?
A
$\Delta {H_{mix}} = 0$
B
$\Delta {U_{mix}} = 0$
C
$\Delta P = {P_{obs}} - P$calculated by Raoult's law
D
$\Delta {G_{mix}} = 0$

## Explanation

For ideal solution, we have

$\Delta$Hmix = 0, $\Delta$Vmix = 0

Now Umix = ∆Hmix – P$\Delta$Vmix

$\therefore$ $\Delta$Umix = 0

Also, for an ideal solution,

pA = xApAo, pB = xBpBo

$\therefore$ $\Delta$p = pobserved – pcalculated = 0

$\Delta$Gmix = $\Delta$Hmix – T$\Delta$Smix

For an ideal solution, $\Delta$Smix $\ne$ 0

$\therefore$ $\Delta$Gmix $\ne$ 0
2

### AIPMT 2015 Cancelled Paper

Which one of the following electrolytes has the same value of van't Hoff factor (i) as that of Al2(SO4)3 (if all are 100% ionised)?
A
Al(NO3)3
B
K4[Fe(CN)6]
C
K2SO4
D
K3[Fe(CN)6]

## Explanation

Ai2(SO4)3 ⇌ 2Al+3 + 3SO42–

van't Hoff factor, i = 5

K2SO4 ⇌ 2K+ + SO42–

van't Hoff factor, i = 3

K3[Fe(CN)6] ⇌ 3K+ + [Fe(CN)6]2-

van't Hoff factor, i = 4

Al(NO3)3 ⇌ Al3+ + 3NO3

van't Hoff factor, i = 4

K4[Fe(CN)6] ⇌ 4K+ + [Fe(CN)6]4–

van't Hoff factor, i = 5
3

### AIPMT 2015 Cancelled Paper

Which of them is not equal to zero for an ideal solution?
A
$\Delta {V_{mix}}$
B
$\Delta P = {P_{observed}} - {P_{Raoult}}$
C
$\Delta {H_{mix}}$
D
$\Delta {S_{mix}}$

## Explanation

For an ideal solution, $\Delta$Smix > 0 while $\Delta$Hmix, $\Delta$Vmix and $\Delta$P all are 0.
4

### AIPMT 2015

What is the mole fraction of the solute in a 1.00 m aqueous solution?
A
1.770
B
0.0354
C
0.0177
D
0.177

## Explanation

Number of moles of water in 1000 g = ${{1000} \over {18}}$ = 55.56 mol

Thus, mole fraction of solute = ${1 \over {1 + 55.56}}$ = 0.0177