M3L12 PAG 3.1

Zinc will displace copper from copper (II) sulphate solution according to the following equation: CuSO₄(aq) + Zn(s) ---------> Cu(s) + ZnSO₄(aq) If an excess of zinc powder is added to 50 cm³ of 1.0 moldm⁻³ copper(II) sulphate, the temperature increases by 6.3ºC. Calculate the enthalpy change for the reaction.

• ΔH = -26.3 kJ/mol

• ΔH = +26.3 kJ/mol

• ΔH = -13.2 kJ/mol

• ΔH = +13.2 kJ/mol

Magnesium will also displace copper from copper (II) sulphate solution. If an excess of magnesium is added to 100 cm³ of 1.0 moldm⁻³ copper(II) sulphate, the temperature increases by 46.3ºC. a) Calculate the molar enthalpy change for the reaction.

• ΔH = -193.3 kJ/mol

• ΔH = -92.5 kJ/mol

• ΔH = -386.6 kJ/mol

• ΔH = -46.3 kJ/mol

Calculate the minimum quantity of magnesium required to ensure it is in excess.

• 2.43 g

• 1.20 g

• 3.50 g

• 0.85 g

Calculate the temperature change if only 0.8g of magnesium is added.

• 15.2ºC.

• 8.7ºC.

• 3.4ºC.

• 21.0ºC.

Calculate the value of q using the formula q = mcΔT, where m = 50 g, c = 4.18 J/g°C, and ΔT = 6.3°C.

• q = 50 x 4.18 x 6.3 = 1314.7 J

• q = 50 x 4.18 x 6.3 = 1047.5 J

• q = 50 x 4.18 x 6.3 = 1200.0 J

• q = 50 x 4.18 x 6.3 = 900.5 J

Calculate the number of moles (n) using the formula n = 1 x 50/1000.

• n = 0.05 mol

• n = 0.5 mol

• n = 0.005 mol

• n = 5 mol

Calculate the enthalpy change (ΔH) using the formula ΔH = -q/n, where q = 1314.7 J and n = 0.05 mol. Give your answer in kJ/mol.

• ΔH = -26.3 kJmol⁻¹

• ΔH = -13.1 kJmol⁻¹

• ΔH = -65.7 kJmol⁻¹

• ΔH = -2.63 kJmol⁻¹

Calculate the value of q using the formula q = mcΔT, where m = 100 g, c = 4.18 J/g°C, and ΔT = 46.3°C.

• q = 100 x 4.18 x 46.3 = 19353.4 J

• q = 100 x 4.18 x 46.3 = 1935.34 J

• q = 100 x 4.18 x 46.3 = 193534 J

• q = 100 x 4.18 x 46.3 = 193.534 J

Calculate the enthalpy change (ΔH) using the formula ΔH = -q/n, where q = 19353.4 J and n = 0.1 mol. Give your answer in kJ/mol.

• ΔH = -193.5 kJmol⁻¹

• ΔH = -19.4 kJmol⁻¹

• ΔH = -1.94 kJmol⁻¹

• ΔH = -0.194 kJmol⁻¹

Calculate the mass using the formula n = 100/1000 x 24.3. What is the mass?

• 2.43 g

• 24.3 g

• 0.243 g

• 243 g