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1

### AIPMT 2002

Reaction BaO2(g) $$\rightleftharpoons$$ BaO(s) + O2(g); $$\Delta$$H = +ve. In equilibrium condition, pressure of O2 depends on
A
increase mass of BaO2
B
increase mass of BaO
C
increase temperature on equilibrium
D
increase mass of BaO2 and BaO both.

## Explanation

For the reaction

BaO2(g) $$\rightleftharpoons$$ BaO(s) + O2(g); H = +ve.

At equilibrium Kp = PO2

[For solid and liquids concentration term is taken as unity]

Hence, the value of equilibrium constant depends only upon partial pressure of O2. Further on increasing temperature formation of O2 increases as this is an endothermic reaction.
2

### AIPMT 2002

Which has highest pH?
A
CH3COOK
B
Na2CO3
C
NH4Cl
D
NaNO3

## Explanation

Na2CO3 is a salt of weak acid H2CO3 and strong base NaOH, therefore, its aqueous solution will be basic hence has pH more than 7.
3

### AIPMT 2002

Solubility of MX2 type electrolytes is 0.5 $$\times$$ 10$$-$$4 mole/lit., then find out Ksp of electrolytes.
A
5 $$\times$$ 10$$-$$12
B
25 $$\times$$ 10$$-$$10
C
1 $$\times$$ 10$$-$$13
D
5 $$\times$$ 10$$-$$13

## Explanation

MX2 Ag2+ + 2X-
s s 2s

Ksp = [M2+] [X]2 = (S)(2S)2 = 4S3

$$\Rightarrow$$ Ksp = 4(0.5 × 10–4)3 = 5 × 10–13
4

### AIPMT 2001

Correct relation between dissociation constants of a dibasic acid is
A
Ka1 = Ka2
B
Ka1 > Ka2
C
Ka1 < Ka2
D
Ka1 = $${1 \over {{K_{{a_2}}}}}$$

## Explanation

In polyprotic acids the loss of second proton occurs much less readily than the first. Usually the Ka values for successive loss of protons from these acids differ by at least a factor of 10–3.

$$\therefore$$ Ka1 > Ka2

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