Calculate the heat evolved per mole in a calorimeter which was open to the air when a mass (m = 2.0 g) of Na2CO3 (s) was added to 100 ml of water. The observed heat rise was 1.5 oC.

PLEASE NOTE: THIS IS AN A-LEVEL QUESTION BUT I WAS UNABLE TO SELECT THAT AS AN OPTION WHEN I ENTERED THE QUESTION! Specific heat capacity of water (c) is 4.181 J g^{-1 o}C^-1 Heat evolved or absorbed = mass x specific heat x temperature change q = m c ΔT q = 100 g x 4.181 J g^{-1 o}C^-1 x 1.5 ^oC= 627.15 J number of moles = mass / molecular mass or n = m / M_r n (Na₂CO₃) = 2 g / 105.99 gmol^-1n = 0.0189 mol => Energy evolved per mole = 627.15 J / 0.0189 mol = 33236 J mol^-1 or 33.2 kJmol^-1 ΔH = -33.2 kJmol^-1