Answer to Question #113857 in General Chemistry for Chan

Question

Suppose you use a constant pressure calorimeter to measure the enthalpy of reaction of the reaction below:
CaO(s) + 2HCl(aq) → CaCl2(aq) + H2O(l)
Suppose you dissolve 0.750g of calcium oxide in 100.0mL of 1M HCl in the calorimeter, and the rise in temperature is measured to be 6.15oC. What is the ΔHrxn? {Specific heat of water = 4.184 J/g.oC; specific heat of the calorimeter = 0.138 J/g.oC; mass of the calorimeter = 51.6g}

Answer 1

First we will calculate heat change due to 0.75 g of CaO and then we will convert it accordingly for 1 mole of CaO

heat generated = mc$\Delta$T=$100\times4.184\times6.15+51.6\times0.138\times6.15=2617 joules$

molar mass of CaO =56

$\Delta H=\frac{56}{0.75}\times2617=195400J$