AP Chemistry 6.6 A Calculate the Heat Q Absorbed or Released By a System Undergoing a Chemical Reaction in Relationship to the Questions

Practice AP Chemistry questions on converting calorimetry heat into reaction enthalpy, using stoichiometric moles, algebraic signs, and energy transfer between system and…

Exam points

Explain how acid-base equilibria depend on proton transfer and conjugate pairs in solution.
Apply pH, pOH and equilibrium relationships to calculate concentrations and predict acid-base changes.

[Maximum number: 2]

White phosphorus is composed of $\mathrm{P}_{4}$ molecules with a tetrahedral structure, as shown in the diagram on the left. Each P atom is bonded to the other three P atoms by single bonds, as shown in the incomplete Lewis diagram on the right.

Figure for Question AP Chemistry 6.6 A Calculate the Heat Q Absorbed or Released By a System Undergoing a Chemical Reaction in Relationship to the Questions question 1 — AP Chemistry

The chemist carries out the calorimetry experiment and records the following information.

Table for Question AP Chemistry 6.6 A Calculate the Heat Q Absorbed or Released By a System Undergoing a Chemical Reaction in Relationship to the Questions question 1 — AP Chemistry

Calculate the value of $\Delta H_{\text {rxn }}^{\circ}$ for equation 2 in $\mathrm{kJ} / \mathrm{mol}_{\text {rxn }}$ . Include the sign in your answer.

(ii) For the correct calculated value, consistent with part C (i):

Point 05

$\begin{aligned} & q_{r x n}=-q_{s u r r}=-0.16 \mathrm{~kJ} \\ & \Delta H_{r x n}^{\circ}=\frac{-0.16 \mathrm{~kJ}}{0.100 \mathrm{~g} \mathrm{P}_{4} \mathrm{O}_{10}} \times \frac{283.9 \mathrm{~g} \mathrm{P}_{4} \mathrm{O}_{10}}{1 \mathrm{~mol} \mathrm{P}_{4} \mathrm{O}_{10}} \times \frac{1 \mathrm{~mol} \mathrm{P}_{4} \mathrm{O}_{10}}{1 \mathrm{~mol}_{r x n}}=-450 \mathrm{~kJ} / \mathrm{mol}_{r x n} \end{aligned}$

For the correct sign:

Point 06

$-450 \mathrm{~kJ} / \mathrm{mol}_{r x n}$

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AP Chemistry 6.6 A Calculate the Heat Q Absorbed or Released By a System Undergoing a Chemical Reaction in Relationship to the Questions question 1