How much oxygen gas (O₂) at standard temperature (0°C) and pressure (1 atm) is required to completely combust 1 liter of propane gas (C₃H₈) under the same conditions?

1.	7L	2.	6L
3.	5L	4.	10L

1 g of magnesium is burnt with 0.56g of oxygen in a closed vessel. The left-out reactant and its quantity are:

(At. weight of Mg = 24, O=16)

Find the minimum molecular weight of the enzyme peroxidase anhydrase if it contains 0.5% selenium by weight.
(Atomic weight of Se = 78.4)

1. 1.568 x 10⁴

2. 15.68

3. 2.168 x 10⁴

4. 1.568 x 10³

The total number of valence electrons in 4.2g of ${\mathrm{N}}_3^{-}$ ion is:
(N_A is the Avogadro's number)

1. 2.1N_A 

2. 4.2N_A 

3. 1.6N_A 

4. 3.2N_A 

Calculate the number of moles of HCl(g) formed when 22.4 L of H₂(g) is mixed with 11.2 L of Cl₂(g), both measured at STP.

1. 1 mole of HCl(g)

2. 2 moles of HCl(g)

3. 0.5 mole of HCl(g)

4. 1.5 moles of  HCl(g)

The mass of carbon anode consumed (giving only carbon dioxide) in the production of 270 kg of aluminium metal from bauxite by the Hall process is (at. mass of Al = 27)

1. 180 kg

2. 270 kg

3. 540 kg

4. 90 kg

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

What is the approximate number of atoms present in 4.25 grams of NH₃?

1. 4 x 10²³ 

2. 2 x 10²³ 

3. 1 x 10²³ 

4. 6 x 10²³ 

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?

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?