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

Find the mass of non-stoichiometric oxide Ti₁.₄₄O formed when 1.44 g of titanium reacts completely with excess O₂.
Given: atomic mass of Ti = 48 g mol⁻¹.

1. 2.00

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

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