3. Thermochemistry
Hess's Law — Quiz
Test your understanding of hess's law with 5 practice questions.
Practice Questions
Question 1
Which of the following properties of enthalpy is fundamental to the application of Hess's Law?
Question 2
Given the following reactions:
$$ \text{C(s)} + \text{O}_2\text{(g)} \rightarrow \text{CO}_2\text{(g)} \quad \Delta H_1 = -393.5 \text{ kJ} $$
$$ \text{H}_2\text{(g)} + \frac{1}{2}\text{O}_2\text{(g)} \rightarrow \text{H}_2\text{O(l)} \quad \Delta H_2 = -285.8 \text{ kJ} $$
$$ \text{CH}_4\text{(g)} + 2\text{O}_2\text{(g)} \rightarrow \text{CO}_2\text{(g)} + 2\text{H}_2\text{O(l)} \quad \Delta H_3 = -890.3 \text{ kJ} $$
Calculate the enthalpy change ($\Delta H$) for the reaction:
$$ \text{C(s)} + 2\text{H}_2\text{(g)} \rightarrow \text{CH}_4\text{(g)} $$
$$ \text{C(s)} + \text{O}_2\text{(g)} \rightarrow \text{CO}_2\text{(g)} \quad \Delta H_1 = -393.5 \text{ kJ} $$
$$ \text{H}_2\text{(g)} + \frac{1}{2}\text{O}_2\text{(g)} \rightarrow \text{H}_2\text{O(l)} \quad \Delta H_2 = -285.8 \text{ kJ} $$
$$ \text{CH}_4\text{(g)} + 2\text{O}_2\text{(g)} \rightarrow \text{CO}_2\text{(g)} + 2\text{H}_2\text{O(l)} \quad \Delta H_3 = -890.3 \text{ kJ} $$
Calculate the enthalpy change ($\Delta H$) for the reaction:
$$ \text{C(s)} + 2\text{H}_2\text{(g)} \rightarrow \text{CH}_4\text{(g)} $$
Question 3
When applying Hess's Law, if a thermochemical equation is multiplied by a factor of $\frac{1}{2}$, what happens to its enthalpy change ($\Delta H$)?
Question 4
Hess's Law is a direct consequence of which fundamental principle of thermodynamics?
Question 5
Given the following reactions:
1. $$ \text{H}_2\text{(g)} + \text{F}_2\text{(g)} \rightarrow 2\text{HF(g)} \quad \Delta H_1 = -546 \text{ kJ} $$
2. $$ 2\text{H}_2\text{(g)} + \text{O}_2\text{(g)} \rightarrow 2\text{H}_2\text{O(l)} \quad \Delta H_2 = -572 \text{ kJ} $$
Calculate the enthalpy change ($\Delta H$) for the reaction:
$$ 2\text{F}_2\text{(g)} + 2\text{H}_2\text{O(l)} \rightarrow 4\text{HF(g)} + \text{O}_2\text{(g)} $$
1. $$ \text{H}_2\text{(g)} + \text{F}_2\text{(g)} \rightarrow 2\text{HF(g)} \quad \Delta H_1 = -546 \text{ kJ} $$
2. $$ 2\text{H}_2\text{(g)} + \text{O}_2\text{(g)} \rightarrow 2\text{H}_2\text{O(l)} \quad \Delta H_2 = -572 \text{ kJ} $$
Calculate the enthalpy change ($\Delta H$) for the reaction:
$$ 2\text{F}_2\text{(g)} + 2\text{H}_2\text{O(l)} \rightarrow 4\text{HF(g)} + \text{O}_2\text{(g)} $$