Q41Short answer
If the combustion of 1g of graphite produces 20.7 kJ of heat, what will be molar enthalpy change? Give the significance of sign also.
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Molar enthalpy = enthalpy change for 1 g carbon × molar mass of carbon change of graphite –1 –1 = – 20.7 kJ g × 12g mol ∴ ∆H = – 2.48 × 102 kJ mol–1 Negative value of ∆H ⇒ exothermic reaction.