Phosphoric acid neutralizes calcium hydroxide according to the balanced equation 2…

CHEMISTRY · Multi-part · A Level · Chemistry · Energetics · Energetics

Problem

Phosphoric acid neutralizes calcium hydroxide according to the balanced equation

\mathrm{2\,H_3PO_4(aq)+3\,Ca(OH)_2(aq)\longrightarrow Ca_3(PO_4)_2(s)+6\,H_2O(l)} \qquad \Delta H = -177\;\text{kJ\,mol}^{-1}

(per mole of reaction as written). A laboratory technician combines

0.300\,\text{mol}

\mathrm{H_3PO_4}

with

0.120\,\text{mol}

\mathrm{Ca(OH)_2}

in a coffee-cup calorimeter containing

1.00\,\text{kg}

of aqueous solution at

25.0\,^{\circ}\text{C}

. Assume the specific heat capacity of the solution is

4.18\,\text{J\,g}^{-1}\,^{\circ}\text{C}^{-1}

and that no heat is lost to the calorimeter or surroundings. Respond to the following prompts. (a) Identify the limiting reactant and justify your choice with calculations. (b) Determine the amount of heat released by the neutralization reaction. (c) Calculate the temperature change

\Delta T

of the solution resulting from the reaction. (d) Compute the number of moles of liquid water produced and the number of moles of excess reactant remaining after the reaction is complete.

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