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1

AIPMT 2015 Cancelled Paper

MCQ (Single Correct Answer)
Solubility of the alkaline earth metal sulphates in water decreases in the sequence
A
Sr > Ca > Mg > Ba
B
Ba > Mg > Sr > Ca
C
Mg > Ca > Sr > Ba
D
Ca > Sr > Ba > Mg

Explanation

Solubility of alkaline earth metal sulphates decreases down the group because hydration energy decreases.
2

AIPMT 2015

MCQ (Single Correct Answer)
On heating which of the following releases CO2 most easily?
A
Na2CO3
B
MgCO3
C
CaCO3
D
K2CO3

Explanation

Carbonates becomes more thermally stable down the group, Also, the alkali metal carbonate are more stable than alkaline earth metal carbonates. Therefore MgCO3 will leave CO2 easily.

MgCO3 $$\buildrel \Delta \over \longrightarrow $$ MgO + CO2
3

AIPMT 2015

MCQ (Single Correct Answer)
20.0 g of a magnesium carbonate sample decomposes on heating to give carbon dioxide and 8.0 g magnesium oxide. What will be the percentage purity of magnesium carbonate in the sample?
(At. wt. of Mg = 24)
A
96
B
60
C
84
D
75

Explanation

MgCO3 $$\buildrel \Delta \over \longrightarrow $$ MgO + CO2

84 g of MgCO3 $$ \equiv $$ 40 g of MgO

$$ \therefore $$ 20 g of MgCO3 = $${{40} \over {84}} \times 20$$ = 9.52 g of MgO

But Actual yield = 8 g of MgO

$$ \therefore $$ % purity = $${8 \over {9.52}} \times 100$$ = 84%
4

NEET 2013 (Karnataka)

MCQ (Single Correct Answer)
In Castner-Kellner cell for production of sodium hydroxide
A
brine is electrolyzed using graphite electrodes
B
molten sodium chloride is electrolysed
C
sodium amalgam is formed at mercury cathode
D
brine is electrolyzed with Pt electrodes

Explanation

In Castner-Kellner cell, sodium amalgam is formed at mercury cathode.

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