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

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

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

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:

Find the concentration of nitrate (NO₃⁻) ions in the mixture formed when equal volumes of 0.1 M AgNO₃ and 0.2 M NaCl solutions are mixed.

One mole of a mixture of CO and CO₂ requires exactly 20 g of NaOH in solution for the complete conversion of all the CO₂ into Na₂CO₃. How much NaOH would it require for conversion into Na₂CO₃, if the mixture (one mole) is completely oxidised to CO₂?

1. 60g

2. 80g

3. 40g

4. 20g

Calculate the change in volume when 100 mL of phosphine ( PH₃) decomposes completely into phosphorus and hydrogen.

Calculate the total molarity of all the ions present in a solution containing 0.1 M of CuSO₄ and 0.1 M of Al₂(SO₄)₃.

1. 0.2M

2. 0.7M

3. 0.8M

4. 1.2M

For the reaction:

4NH₃(g) + 5O₂(g) → 4NO(g) + 6H₂O(l)

If 1 mol of NH₃ is mixed with 1 mol of O₂ and the reaction proceeds to completion, which of the following statements is correct?

In the Haber process, 30 L of H₂ and 30 L of N₂ are allowed to react. If the reaction gives only 50% of the theoretically expected yield of NH₃, what will be the composition of the gaseous mixture at the end of the reaction?

1. 20 L ammonia, 10 L nitrogen, 30 L hydrogen

2. 10 L ammonia, 25 L nitrogen, 15 L hydrogen

3. 20 L ammonia, 20 L nitrogen, 20 L hydrogen

4. 20 L ammonia, 25 L nitrogen, 15 L hydrogen