Enthalpy change question?
Magnesium will 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 46.3 oC.
Calculate the temperature change if only 0.8 g of magnesium is added.
- 冷眼旁觀Lv 61 month agoFavorite Answer
Equation for the reaction:
Mg(s) + CuSO₄(aq) → MgSO₄(aq) + Cu(s)
Mole ratio Mg : CuSO₄ = 1 : 1
When Mg is in excess:
Moles of HCl reacted = (1.0 mol dm⁻³) × (100/1000 dm³) = 0.1 mol
When 0.1 mol HCl reacts, temperature increases by 46.3°C.
When only 0.8 g of Mg (Molar mass = 24.3 g/mol) is added:
Moles of Mg reacted = (0.8 g) / (24.3 g/mol) = 0.0329 mol
Hence, moles of HCl reacted = 0.0329 mol
Temperature increases by (46.3 °C) × (0.0329/0.1) = 15.2°C