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.

1 Answer

Relevance
  • 1 month ago
    Favorite 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

    • Acacia4 weeks agoReport

      thanks for your detailed answer but why did you divide 0.0329 by 0.1?

    • Login to reply the answers
Still have questions? Get your answers by asking now.