Method of Calculating Δ H a ) Quantity of heat change in a substance depends on ( kuantiti perubahan haba bg sesuatu bahan bergantung kepada ): i - Mass of substance (m in grams) ii- Specific heat capacity of a substance (c in Jg -1 o C -1 ) iii- Temperature change ( θ in o C ) b) As chemical reaction occurs in an aqueous solution, assumptions are made during the calculation of heat of reaction : Density of aq solution = Density of water = 1 g cm -3 Density of aq solution = Density of water = 1 g cm -3 Example : - 1 cm 3 of aq solution has a mass of 1 g - 2 cm 3 of aq solution has a mass of 2g Specific heat capacity of solution = Specific heat capacity of water = 4.2 Jg -1 o C -1 The heat of reaction can be calculated by using formula Energy change, H = mc θ Four type of heat of reaction : 1) Heat of precipitation - Heat of precipitation is heat change when 1 mole of precipitate is formed from its ions. 2) Heat of displacement - Heat of displacem
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