Titanium(IV) chloride can be made from titanium(IV) oxide as shown in the equation - AQA - A-Level Chemistry - Question 5 - 2017 - Paper 1

We start by calculating the change in entropy (ΔS) using the formula:

$$ΔS = S_{products} - S_{reactants}$$

Where:

• For the products (2 CO(g) + TiCl₄(l)):
  • 2 × 198 J K⁻¹ mol⁻¹ (for CO) + 253 J K⁻¹ mol⁻¹ (for TiCl₄)
• For the reactants (TiO₂(s) + 2C(s) + 2Cl₂(g)):
  • 50.2 J K⁻¹ mol⁻¹ (for TiO₂) + 2 × 5.7 J K⁻¹ mol⁻¹ (for C) + 2 × 223 J K⁻¹ mol⁻¹ (for Cl₂)

Calculating:

• Products: 2 × 198 + 253 = 649 J K⁻¹ mol⁻¹
• Reactants: 50.2 + 2 × 5.7 + 2 × 223 = 507.6 J K⁻¹ mol⁻¹

Thus:

$$ΔS = 649 - 507.6 = 141.4 \, J \, K^{-1} \, mol^{-1}$$