PART A
EXPERIMENT 1
Question 1.1 [1 mark]
Aim: To investigate the temperature changes that occur when different salts dissolve in water.
Question 1.2 [1 mark]
Solvent: Water
Question 1.3 [8 marks]
| Salts | Final Temperature of the Solution (°C) | Ionic Equation | |-------------------|-----------------------------------------|-------------------------------------------------------------------------------| | NaOH | a. ________________ | b. NaOH(s) → Na⁺(aq) + OH⁻(aq) | | CaCl₂ | c. ________________ | d. CaCl₂(s) → Ca²⁺(aq) + 2 Cl⁻(aq) | | MgSO₄ | e. ________________ | f. MgSO₄(s) → Mg²⁺(aq) + SO₄²⁻(aq) | | KNO₃ | g. ________________ | h. KNO₃(s) → K⁺(aq) + NO₃⁻(aq) |
(Note: The final temperature values must be provided based on actual experimental data.)
Question 1.4 [2 marks]
Exothermic Reactions: The dissolution of salts that resulted in an increase in temperature indicates an exothermic reaction (e.g., NaOH and CaCl₂, depending on the results recorded).
Question 1.5 [2 marks]
Endothermic Reactions: The dissolution of salts that resulted in a decrease in temperature indicates an endothermic reaction (e.g., KNO₃ or MgSO₄, depending on the results recorded).
Question 1.6 [2 marks]
The test tube (or beaker) of the endothermic reaction would feel cool to the touch. This is because the reaction absorbs heat from the surroundings, resulting in a decrease in temperature of the solution and the container.
PART A
EXPERIMENT 2
Question 2.1 [2 marks]
Balanced Chemical Equation:
\[ Mg(s) + CuSO₄(aq) \rightarrow MgSO₄(aq) + Cu(s) \]
Question 2.2 [3 marks]
To calculate the number of moles of copper sulfate (CuSO₄) present in 3.99 g:
- Molar mass of CuSO₄ = 63.55 (Cu) + 32.07 (S) + 64.00 (4 O) = 159.62 g/mol
- Moles of CuSO₄ = Mass (g) / Molar Mass (g/mol)
\[ \text{Moles of } CuSO₄ = \frac{3.99 , g}{159.62 , g/mol} \approx 0.025 , \text{mol} \]
(rounded to 3 decimal places)
Question 2.3 [3 marks]
From the balanced equation, 1 mole of Mg displaces 1 mole of Cu. Thus, 0.025 moles of Cu are displaced.
- Molar mass of Cu = 63.55 g/mol
- Mass of Cu = Moles × Molar Mass = \( 0.025 , mol \times 63.55 , g/mol \approx 1.589 , g \)
Question 2.4 [1 mark]
Difference in Temperature:
\[ \text{Difference} = \text{Final Temperature} - \text{Initial Temperature} \]
Question 2.5 [2 marks]
If the temperature increases, the reaction is exothermic; if it decreases, it is endothermic. The conclusion should specify which observation corresponds to which type of reaction based on the temperature difference calculated.
Question 2.6 [4 marks]
Potential Energy Profile Diagram:
- Label the Y-axis as "Potential Energy."
- The X-axis should represent "Progress of the Reaction."
- Mark the following:
- Reactants (higher PE)
- Products (lower PE, if exothermic)
- Activated Complex (peak energy)
- The difference in energy levels should indicate \(\Delta H\).
Question 2.7 [1 mark]
On the same diagram, use a dotted line to represent the effect of a catalyst, which would lower the activation energy (\(E_a\)) without changing the overall enthalpy change (\(\Delta H\)).
PART B
Question 3.1 [4 marks]
Lewis Structures:
- 3.1.1 N₂:
N≡N
- 3.1.2 NO:
:N=O:
Question 3.2
-
Question 3.2.1 [2 marks]
Total Energy to Break Bonds of Reactants:- Energy required = Energy of N≡N + Energy of O=O
\[ = 945.36 , kJ/mol + 498 , kJ/mol = 1443.36 , kJ/mol \]
- Energy required = Energy of N≡N + Energy of O=O
-
Question 3.2.2 [3 marks]
Total Energy Released for Products:- There are two N=O bonds formed, so: \[ \text{Energy released} = 2 \times 607 , kJ/mol = 1214 , kJ/mol \]
Question 3.3 [2 marks]
Heat of Reaction (Enthalpy Change):
\[ \Delta H = \text{Energy of bonds broken} - \text{Energy of bonds formed} \]
\[ \Delta H = 1443.36 , kJ/mol - 1214 , kJ/mol = 229.36 , kJ/mol \]
Question 3.4 [2 marks]
Type of Reaction:
The reaction is endothermic because the total energy required to break the bonds is greater than the energy released upon forming the new bonds.
Question 3.5 [5 marks]
Potential Energy Graph:
- Draw the potential energy on the Y-axis and the reaction progress on the X-axis.
- Indicate the energy of reactants, products, and the peak representing the activated complex.
- Include the labels for \(\Delta H\), Energy of reactants (ER), Energy of products (EP), and Activation Energy (E_a).
This concludes the lab report structure for the experiments according to the given format. Adjust results as necessary based on actual experimental data.
1 answer