Find the percentage of oxygen present in the compound CaCO₃ and Ca₃(PO₄)₂.

1.  23.3%

2.  45.36%

3.  41.94%

4.  17.08%

A gaseous compound is composed of 85.7% by mass carbon and 14.3% by mass hydrogen. It's density is 2.28 g/litre at 300 K and 1.0 atm pressure. Determine the molecular formula of the compound:

1.  ${\mathrm{C}}_2{\mathrm{H}}_2$

2.  ${\mathrm{C}}_2{\mathrm{H}}_4$

3.  ${\mathrm{C}}_4{\mathrm{H}}_8$

4.  ${\mathrm{C}}_4{\mathrm{H}}_{10}$

Calculate the % of free ${\mathrm{SO}}_3$ in oleum (a solution of ${\mathrm{SO}}_3$ in ${\mathrm{H}}_2{\mathrm{SO}}_4$) that is labelled 109% ${\mathrm{H}}_2{\mathrm{SO}}_4$.

1. 40

2. 30

3. 50

4. None

Suppose two elements X and Y combine to form two compounds ${\mathrm{XY}}_2$ and ${\mathrm{X}}_2{\mathrm{Y}}_3$when 0.05 mole of${\mathrm{XY}}_2$ weighs 5 g while 3.011$\times$10²³ molecules of ${\mathrm{X}}_2{\mathrm{Y}}_3$ weighs 85 g. The atomic masses of x and y are respectively:

1.  20, 30

2.  30, 40

3.  40, 30

4.  80, 60

100 mL of 10% NaOH (w/V) is added to 100 mL of 10% HCl (w/V). The resultant solution becomes:

1. Alkaline

2. Strongly alkaline

3. Acidic

4. Neutral

1.44 gram of titanium (At. wt. =48) reacted with excess of ${\mathrm{O}}_2$ and produce x gram of non-stoichiometric compound Ti_1.44 O$$. The value of x is:

1. 2

2. 1.77

3. 1.44

4. None of the above

2Fe(NO₃)₃ + 3Na₂CO₃ → Fe₂(CO₃)₃ + 6NaNO₃

A 6.0 g impure sample of sodium chloride is dissolved in water and reacted with excess silver nitrate solution.
If 14.0 g of silver chloride is formed, determine the percentage purity of NaCl in the sample.

1. 95%

2. 85%

3. 75%

4. 65%

The vapour density of a mixture containing \(NO_{2}\) and \(N_{2} O_{4}\)  is 38.3. The mole of \(NO_{2}\) in a 100 g mixture is:

[Vapour density = (Molar mass / 2)]

1. 0.437

2. 0.347

3. 0.557

4. 0.663

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

1. 2:5

2. 1:6

3. 2:1

4. 1:2