CaO(s)reacts with water to form Ca(OH)₂(aq).If 6.50 g CaO is combined with 99.70 g H₂O in a coffee cup calorimeter,the temperature of the resulting solution increases from 21.7 °C to 43.1 °C.Calculate the enthalpy change for the reaction per mole of CaO.Assume that the specific heat capacity of the solution is 4.18 J/g⋅K.

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Quizplus · Accepted Answer

The enthalpy change for the reaction per mole of CaO can be calculated using the formula $q = mc\Delta T$, where $m$ is the mass of the solution, $c$ is the specific heat capacity, and $\Delta T$ is the change in temperature. The total mass of the solution is the sum of the masses of CaO and $H_2O$, which is $6.50 g + 99.70 g = 106.20 g$. The change in temperature, $\Delta T$, is $43.1 °C - 21.7 °C = 21.4 °C$. Therefore, $q = 106.20 g \times 4.18 J/g⋅K \times 21.4 K = 9505.4 J$ or $9.5054 kJ$. Since the molar mass of CaO is approximately 56.08 g/mol, the number of moles of CaO is $6.50 g / 56.08 g/mol = 0.1159 mol$. The enthalpy change per mole of CaO is $9.5054 kJ / 0.1159 mol = 82.0 kJ/mol$, but since the reaction is exothermic (releases heat), the enthalpy change is negative, hence $-82.0 kJ/mol$.

CaO(s)reacts with Water to Form Ca(OH)2(aq)

CaO(s)reacts with Water to Form Ca(OH)₂(aq)