Q1. A student investigated the temperature change when zinc reacts with copper sulfate solution. The student used a different concentration of copper sulfate solution for each experiment. The student used the apparatus shown below:
Zn(s) + copper sulfate
(a) The student:
- measured 50 cm³ copper sulfate solution into a glass beaker
- measured the temperature of the copper sulfate solution
- added 2.3 g zinc
- measured the highest temperature
- repeated the experiment using copper sulfate solution with different concentrations.
The equation for the reaction is:
2.3 g zinc + CuSO.(aq) → ZnSO.(aq) + Cu(s)
Improvement
The thermometer reading changes during the reaction. Give one other change the student could see during the reaction. Suggest one improvement the student could make to the apparatus. Give a reason why this improves the investigation.
(1)
The figure below shows magnesium burning in air.
(a) Look at the figure above. Charles D Winters/Science Photo Library. How can you tell that a chemical reaction is taking place? Name the product from the reaction of magnesium in the figure. The magnesium needed heating before it would react. What conclusion can you draw from this?
Tick one box.
Q1. This question is about the reaction of ethene and bromine. The equation for the reaction is: C2H4 + Br2 → C2H4Br2 (a) Complete the reaction profile in Figure 1. Draw labelled arrows to show: ● The energy given out (AH) ● The activation energy.
Energy Figure 1.
C2H4 + Br2 ———→ C2H4Br2 (b) When ethene reacts with bromine, energy is required to break covalent bonds in the molecules. Explain how a covalent bond holds two atoms together.
The bond enthalpies and the overall energy change are shown in the table below. Use the information in the table above and Figure 2 to calculate the bond energy for the Br-Br bond.
(d) Figure 3 shows the reaction between ethene and chlorine and is similar to the reaction between ethene and bromine.
Overall energy change -95. kJ/mole. "The more energy levels (shells) of electrons an atom has, the weaker the covalent bonds that it forms." Use the above statement to predict and explain how the overall energy change for the reaction of ethene with chlorine will differ from the overall energy change for the reaction. The reaction is reversible. The reaction has a high activation energy. The reaction is exothermic. Magnesium has a high melting point.
(d) A sample of the product from the reaction in the figure above was added to water and shaken. Universal indicator was added. The universal indicator turned blue. What is the pH value of the solution?
(e) Why are nanoparticles effective in very small quantities?
Tick one box. They are elements. They are highly reactive.
Reason (c) In this question you will be assessed on using good English, organizing information clearly and using specialist terms where appropriate. The student's results are shown in the table.
Experiment number
1
2
3
4
5
6
7
8
9
10
Concentration of copper sulfate in moles per dm3
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
1.0
Table Increase in temperature in °C
5
10
12
20
25
30
35
35
35
35
Describe and Explain the Trends Shown in the Student's Results
(f) They have a low melting point They have a high surface area to volume ratio (h) Give one advantage of using nanoparticles in sun creams.
(g) Give one disadvantage of using nanoparticles in sun creams. A coarse particle has a diameter of 1 x 10-6 m. A nanoparticle has a diameter of 1.6 x 10⁹ m.
Calculate how many times bigger the diameter of the coarse particle is than the diameter of the nanoparticle.
Q2. A student investigated displacement reactions of metals. The student added different metals to copper sulfate solution and measured the temperature change. The more reactive the metal is compared with copper, the bigger the temperature change. The apparatus the student used is shown in Figure 1.
(b) State three variables that the student must control to make his investigation a fair test. 1 2 3 -Thermometer -Copper sulfate solution -Metal
Before adding metal
After adding metal
Q2. This question is about ethanol. (a) (b) Ethanol is produced by the reaction of ethene and steam: C₂H₂ + H₂O (i) Figure 1 shows the energy level diagram for the reaction.
Conclusion
In conclusion, it's important for students to understand the principles of investigating temperature change in chemical reactions. By following the correct procedures and considering various factors, accurate results can be obtained. This knowledge is crucial for understanding exothermic and endothermic reactions exam questions and other related topics.
