1

### AIPMT 2015 Cancelled Paper

The function of ''Sodium pump'' is a biological process operating in each and every cell of all animals. Which of the following biologically important ions is also a constituent of this pump?
A
K+
B
Fe2+
C
Ca2+
D
Mg2+

## Explanation

K+ ion is a constituent of sodium pump.
2

### AIPMT 2015

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%
3

### AIPMT 2015

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
4

### NEET 2013 (Karnataka)

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.