Titanium is a transition metal - AQA - GCSE Chemistry - Question 8 - 2018 - Paper 1

Water is hazardous when in contact with sodium because it produces a very exothermic reaction that can generate hydrogen gas, which is flammable.

The reaction is carried out in an atmosphere of argon to prevent any reaction with oxygen or moisture from the air, which could lead to unwanted side reactions or reduce the yield of titanium.

Titanium chloride is generally expected to be a solid at room temperature due to its ionic character. Ionic compounds typically have high melting points due to strong electrostatic forces between ions, which would not allow them to remain liquid under normal conditions.

This is an oxidation reaction because sodium atoms lose electrons and are transformed into sodium ions (Na → Na⁺ + e⁻), demonstrating the characteristic loss of electrons that defines oxidation.

The completed half equation for the oxidation reaction is:

Na → Na⁺ + e⁻

To determine why titanium chloride (TiCl₄) is the limiting reactant, we need to calculate the moles of each reactant involved.

1. Calculate the moles of Na:

   Given mass = 20 kg = 20000 g.

   Molar mass of Na = 23 g/mol,

   Moles of Na = 20000 g / 23 g/mol = 869.57 mol.

2. For the reaction, 4 moles of Na react with 1 mole of TiCl₄:

   Thus, moles of TiCl₄ needed = (869.57 mol Na) / 4 = 217.39 mol.

3. Calculate the moles of TiCl₄ from mass:

   Mass of TiCl₄ = 40 kg = 40000 g.

   Molar mass of TiCl₄ = 190 g/mol,

   Moles of TiCl₄ = 40000 g / 190 g/mol = 210.53 mol.

As we require 217.39 mol of TiCl₄ and only have 210.53 mol available, TiCl₄ is the limiting reactant.

To find the actual mass of titanium produced:

1. Calculate the theoretical mass of titanium:

   • Theoretical yield = 13.5 kg,
   • Percentage yield = 92.3%.

2. Use the formula for actual yield:

   Actual mass = (Percentage yield / 100) × Theoretical mass = (92.3 / 100) × 13.5 = 12.5 kg.

Thus, the actual mass of titanium produced is 12.5 kg.