Formulae, Equations & Avogadro (Edexcel A Level Chemistry)

What is the total number of ions in 26.4 g of ammonium sulfate, (NH₄)₂SO₄?

[Molar mass of (NH₄)₂SO₄ = 132 g mol⁻¹           Avogadro constant = 6.0 × 10²³ mol⁻¹]

How many ions are present in 306 g of aluminium oxide, Al₂O₃ ?

[Avogadro constant = 6.02 × 10²³ mol⁻¹ Molar mass of Al₂O₃ = 102 g mol⁻¹ ]   

This question is about the chemistry of hydrated magnesium nitrate, Mg(NO₃)₂.xH₂O.

Group 2 nitrates decompose when heated.

(3)

This question concerns iodine monochloride, ICl, a red‐brown solid which melts at 27 °C to form a red‐brown liquid.

Iodine monochloride is used in measuring unsaturation in organic compounds.

Iodine monochloride gas can be produced by the reaction between iodine vapour and chlorine gas. The reaction is exothermic.

I₂ (g) + Cl₂ (g) → 2ICl (g)                        Δ_rH = −30 kJ mol⁻¹

The table shows bond energy values for the bonds in iodine and chlorine.

Calculate the value of the bond energy of the I—Cl bond using these data and the equation.

Iodine monochloride is a polar molecule which adds rapidly to double bonds in a similar way to hydrogen chloride. This reaction can be used to determine the degree of unsaturation in oils.

(1)

I—Cl

(3)

ICl + KI → I₂ + KCl

The amount of iodine produced was measured by reacting the mixture with a solution of sodium thiosulfate, Na₂S₂O₃.

The iodine released reacted with 32.65 cm³ of 0.100 mol dm⁻³ sodium thiosulfate solution in the mole ratio of 1 mol I₂ : 2 mol Na₂S₂O₃.

Calculate the number of moles of iodine monochloride which reacted with 0.250 g of the oil.

(3)

Given that 1 mol of I₂ is equivalent to 1 mol of ICl, use your answer in (c)(i) to calculate the mass of iodine that would react with 100 g of oil and hence identify the unsaturated oil from the list of possible oils and their iodine numbers.

(2)