Let's answer **question 6** in two steps, with explanations at each step: --- ## Step 1: Write the relationship Recall the relationship given in the hint: \[ n\Delta H_{rxn} = mc\Delta T \] Where: - \( n \) = moles of limiting reactant - \( \Delta H_{rxn} \) = molar enthalpy change - \( m \) = mass of water - \( c \) = specific heat capacity of water - \( \Delta T \) = temperature change We solve for \( \Delta T \): \[ \Delta T = \frac{n\Delta H_{rxn}}{mc} \] **Explanation:** This equation shows that temperature change (\( \Delta T \)) is directly proportional to the number of moles reacting (if water mass is constant), and inversely proportional to the mass of water (if moles reacting are constant). --- ## Step 2: Analyze Each Case ### a) **Group 1 doubled the water’s volume but kept the mass of iron the same.** - Mass of water doubles (\( m \rightarrow 2m \)), but moles of iron (and thus \( n \)) are the same. - Using the equation above: \[ \Delta T_{new} = \frac{n\Delta H_{rxn}}{2mc} = \frac{1}{2}\left(\frac{n\Delta H_{rxn}}{mc}\right) = \frac{1}{2}\Delta T_{original} \] **Explanation:** Doubling the mass of water while keeping everything else constant will **halve the temperature change**. --- ### b) **Group 2 doubled the mass of iron but kept the water’s volume the same.** - Moles of iron (\( n \)) double, but mass of water is constant. - Using the equation above: \[ \Delta T_{new} = \frac{2n\Delta H_{rxn}}{mc} = 2\left(\frac{n\Delta H_{rxn}}{mc}\right) = 2\Delta T_{original} \] **Explanation:** Doubling the amount of iron (with excess oxygen and same water mass) will **double the temperature change**. --- ## **Final Answers** ### a) The temperature change will be **halved**. ### b) The temperature change will be **doubled**.

# Question 7: Improvement Suggestion ## Suggestion for Calorimeter Design ### Improvement - **Insulation Enhancement:** Increase the thermal insulation of the calorimeter to minimize heat exchange with the environment. ### Explanation Improving insulation will ensure that more of the heat generated by the reaction is absorbed by the water, leading to more accurate temperature measurements. --- # Question 8: Chemical Equations with Molar Enthalpy ## a) Chemical Equation with Molar Enthalpy (Iron) ### Equation \[ 4 \text{Fe}(s) + 3 \text{O}_2(g) + \Delta H = 2 \text{Fe}_2\text{O}_3(s) \] ### Explanation The enthalpy change (\( \Delta H \)) is included as a product, indicating heat is released during the reaction. --- ## b) Chemical Equation with Molar Enthalpy (Oxygen) ### Equation \[ 4 \text{Fe}(s) + 3 \text{O}_2(g) \rightarrow 2 \text{Fe}_2\text{O}_3(s) + \Delta H \] ### Explanation Here, the enthalpy change is shown as a separate term, indicating it is associated with the oxygen used in the reaction. --- ## c) Potential Energy Diagram ### Diagram Description - **Y-axis:** Potential Energy - **X-axis:** Reaction Progress - **Reactants:** \(4 \text{Fe} + 3 \text{O}_2\) at a higher energy level - **Products:** \(2 \text{Fe}_2\text{O}_3\) at a lower energy level - **Activation Energy:** A peak indicating the energy required to initiate the reaction. - **Enthalpy Change (\( \Delta H \))**: The difference in energy between reactants and products, indicated as a downward arrow. ### Explanation This diagram visually represents the energy changes during the reaction, showing that energy is released as the reaction proceeds from reactants to products.