An element X occurs naturally as three isotopes with the following abundances:

²⁰⁰X = 90%, ¹⁹⁹X = 8%, and ²⁰²X = 2%.

What is the approximate average atomic mass of element X?

1.	205 u	2.	220 u
3.	196 u	4.	200 u

Calculate the vapour density of a volatile gas if 0.24 g of the gas produces 45 mL of vapour at NTP.
(Given that the density of hydrogen at STP is 0.08988 g L⁻¹).

1. 95.93

2. 59.93

3. 95.39

4. 69.93

A hydrated sodium sulphate salt, Na₂SO₄·nH₂O, loses 55% of its mass on heating to form anhydrous Na₂SO₄. What is the value of n?

12 g of Mg (atomic mass = 24) will react completely with an acid to yield:

1. One mole of H₂ 

2. A half mole of H₂

3. One mole of O₂

4. None of the above

The molality of a 15% (w/vol.) solution of H₂SO₄ of density 1.1g/cm³ is:

1. 1.2 mol/kg

2. 1.4 mol/kg

3. 1.8 mol/kg

4. 1.6 mol/kg

H₃PO₄ is a tribasic acid and one of its salts is NaH₂PO₄. What volume of 1 M NaOH should be added to 12g NaH₂PO₄ (Molar mass 120) to exactly convert it into Na₃PO₄?

1. 100 mL

2. 300mL

3. 200mL

4. 80mL

Which mode of expressing concentration is independent of temperature?

1. Molality

2. Percent by mass

3. Mole fraction

4. All of the above 

The product of atomic mass and specific heat of metal is approximately 6.4. This was given by:

1. Dalton's law

2. Avogadro's law

3. Newton's law

4. Dulong Petit's law

A metal M forms a compound M₂HPO₄. The formula of the metal sulphate is:

1. M₂SO₄ 

2. MSO₄

3. M(SO₄${)}_2$

4. M₂(SO₄)₃

A partially dried clay mineral contains 8% water. The original sample contained 12% water and 45% silica. The percentage of silica  in the partially dried sample is nearly: