1

### NEET 2013 (Karnataka)

In an experiment it showed that 10 mL of 0.05 M solution of chloride required 10 mL of 0.1 M solution of AgNO3, which of the following will be the formula of the chloriode (X stands for the symbol of the element other than chlorine)
A
X2Cl2
B
XCl2
C
XCl4
D
X2Cl

## Explanation

Milimoles of solution of chloride = 0.05 $\times$ 10 = 0.5

Millimoles of AgNO3 solution = 10 $\times$ 0.1 = 1

So, the millimoles of AgNO3 are double than the chloride solution.

$\therefore$ XCl2 + 2AgNO3 $\to$ 2AgCl + X(NO3)2
2

### NEET 2013

6.02 $\times$ 1020 molecules of urea present in 100 mL of its solution. The concentration of solution is
A
0.001 M
B
0.1 M
C
0.02 M
D
0.01 M

## Explanation

Moles of urea = ${{6.02 \times {{10}^{20}}} \over {6.02 \times {{10}^{23}}}} = 0.001$

Concentration of solution = ${{0.001} \over {100}} \times 1000$ = 0.01 M
3

### AIPMT 2011 Mains

Which has the maximum number of molecules among the following ?
A
44 g CO2
B
48 g O3
C
8 g H2
D
64 g SO2

## Explanation

8 g H2 has 4 moles while the others has 1 mole each.
4

### AIPMT 2010 Prelims

25.3 g of sodium carbonate, Na2CO3 is dissolved in enough water to make 250 mL of solution. If sodium carbonate dissociates completely, molar concentration of sodium ion, Na+ and carbonate ions, CO${}_3^{2 - }$ are respectively (Molar mass of Na2CO3 = 106 g mol$-$1)
A
0.955 M and 1.910 M
B
1.910 M and 0.955 M
C
1.90 M and 1.910 M
D
0.477 M and 0.477 M

## Explanation

Given in the question that molar mass of Na2CO3 = 106 g

$\therefore$ Molarity of solution = ${{25.3 \times 1000} \over {106 \times 250}}$

= 0.9547 M = 0.955 M

Na2CO3 $\to$ 2Na+ + $CO_3^{2-}$

[Na+] = 2[Na2CO3] = 2 $\times$ 0.955 = 1.910 M

[$CO_3^{2-}$] = [Na2CO3] = 0.955 M