When 1.4 g of ethene gas, C ₂ H ₄( g ) , is completely burned in a bomb calorimeter, the temperature of the calorimeter increases by 5 K . The heat capacity of the calorimeter is 14 kJ K ⁻¹ . Given: Standard enthalpy of formation of CO ₂( g ) = -394 kJ mol ⁻¹ Standard enthalpy of formation of H ₂ O ( l ) = -286 kJ mol ⁻¹ Assume RT = 2.5 kJ mol ⁻¹ and molar mass of C ₂ H ₄ = 28 g mol ⁻¹ . The standard enthalpy of form

Step-by-step solution

First, calculate the number of moles of ethene burned: n = 1.4 28 = 0.05 mol The heat released at constant volume (which corresponds to U ) is: q = C T = 14 5 = 70 kJ Since heat is released, U _c for 0.05 mol is -70 kJ . For 1 mol of ethene, U _c = -70 0.05 = -1400 kJ mol ⁻¹ . The balanced combustion equation for ethene is: C ₂ H ₄( g ) + 3 O ₂( g ) 2 CO ₂( g ) + 2 H ₂ O ( l ) Calculate the change in gaseous moles ( n_g ): n_g = n_p( gas ) - n_r( gas ) = 2 - (1 + 3) = -2 Now, calculate the standard enthalpy of comb