Copper forms two oxides. For the same amount of copper, twice as much oxygen was used to form first oxide than to form second one. What is the ratio of the valencies of copper in first and second oxides?

1. 2:5

2. 1:6

3. 2:1

4. 1:2

5 mL of a gaseous hydrocarbon was exposed to 30 mL of ${\mathrm{O}}_2$. The resultant gas, on cooling is found to measure 25 mL of which 10 mL is absorbed by NaOH and the remainder by pyrogallol. Determine molecular formula of hydrocarbon. All measurements are made at constant room temperature.

1. CH₄

2. C₂H₂

3. C₃H₄

4.C₂H₄

2.0 g sample containing ${\mathrm{Na}}_2{\mathrm{CO}}_3$and ${\mathrm{NaHCO}}_3$ loses 0.248 g when heated to 300$°$C, the temperature at which ${\mathrm{NaHCO}}_3$ decomposes to ${\mathrm{Na}}_2{\mathrm{CO}}_3$, ${\mathrm{CO}}_2$ and ${\mathrm{H}}_2\mathrm{O}$. What is the % of ${\mathrm{Na}}_2{\mathrm{CO}}_3$ in mixture?

1.66.5

2.50.6

3.60.5

4.6.65

A sample of ${\mathrm{CaCO}}_3$ and ${\mathrm{MgCO}}_3$ weighed 2.21 g is ignited to constant mass of 1.152 g. Calculate the volume of ${\mathrm{CO}}_2$ evolved at $0°\mathrm{C}$ and 76 cm of pressure.

1.640 ml

2.540 ml

3.500 ml

4.600 ml

The average molar mass of the mixture of ${\mathrm{CH}}_4$ $$and ${\mathrm{C}}_2{\mathrm{H}}_4$ present in the mole ratio of a:b is
20 g mol^-1. When the mole ratio is reversed, the molar mass of the mixture will be:

Vapour density of a volatile substance is 4 $\left({\mathrm{CH}}_4=1\right)$. Its molar mass would be:

1.  8

2.  2

3.  64

4.  128

The vapour density of a volatile chloride of a metal is 95 and the specific heat of the metal is 0.13 cal/g. The equivalent mass of the metal will be:

1.  6 g
2. 12 g
3.  18 g
4.  24 g

${\mathrm{O}}_3$ is absorbed by:

1.  Pyrogallol

2.  Menthol

3.  Turpentine oil

4.  Clove oil

The mass of one molecule of compound ${\mathrm{C}}_{60} {\mathrm{H}}_{122}$ is:

1.  $1.3\times {10}^{-20} \mathrm{g}$

2.  $5.01\times {10}^{-21} \mathrm{g}$

3.  $3.72\times {10}^{-23} \mathrm{g}$

4.  $1.4\times {10}^{-21} \mathrm{g}$

Read the following statements (S) and Explanation (E). Choose the correct answers from the codes (1), (2), (3) and (4):

S : An element may have variable equivalent mass.

E : Such elements should possess variable valency. 

1.  S is correct but E is wrong
2.  S is wrong but E is correct
3.  Both S and E are correct and E is correct explanation of S
4.  Both S and E are correct but E is not correct explanation of S