Data Booklet - AS/A Level Chemistry

Data Booklet - AS/A Level Chemistry

Chemistry   16:05

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(HANDOUT) IGCSE Chemistry-Redox Reactions

(HANDOUT) IGCSE Chemistry-Redox Reactions

reduction   13:53

REDOX REACTIONS

• Redox stands for reduction oxidation.
• Redox reaction, also called oxidation reduction reaction, is a chemical reaction in which one substance is reduced and another is oxidised simultaneously.
• Oxidation and reduction of substances occur simultaneously. As one substance is reduced the other is oxidised.
• An oxidising agent is a substance that causes the oxidation of the other substance. Therefore, the substance that is reduced in a reaction is the oxidising agent.
• A reducing agent is a substance that causes the reduction of the other substance. For example, the substance that is oxidised in a reaction is the reducing agent.

OXYGEN IN REDOX REACTION

• Oxidation is the gain of oxygen by the substance. A substance that has gained oxygen is said to be oxidised.
• Reduction is the loss of oxygen by the substance. A substance that has lost oxygen is said to be reduced.

HYDROGEN IN REDOX REACTION

• Oxidation is the loss of hydrogen by the substance. A substance that has lost hydrogen is said to be oxidised.
• Reduction is the gain of hydrogen by the substance. A substance that has gained hydrogen is said to be reduced.

ELECTRONS IN REDOX

• Oxidation is the loss of electrons. A substance that loses electrons is oxidised.
• Reduction is the gain of electrons. A substance that gains electrons is reduced.
• The reaction below shows a redox reaction involving the gain and loss of electrons. 

OXIDATION NUMBER

• Oxidation number, also called oxidation state, is the number of electrons an atom gains or losses in a chemical combination. 

 

REDOX REACTION PRESENTATION

REDOX REACTION PRESENTATION

reduction   13:44

 REDOX REACTIONS

• Redox stands for reduction oxidation.
• Redox reaction, also called oxidation reduction reaction, is a chemical reaction in which one substance is reduced and another is oxidised simultaneously.
• Oxidation and reduction of substances occur simultaneously. As one substance is reduced the other is oxidised.
• An oxidising agent is a substance that causes the oxidation of the other substance. Therefore, the substance that is reduced in a reaction is the oxidising agent.
• A reducing agent is a substance that causes the reduction of the other substance. For example, the substance that is oxidised in a reaction is the reducing agent.  

IGCSE Chemical Energetics Essay (with the answer key)

IGCSE Chemical Energetics Essay (with the answer key)

IGCSE Chemistry   13:36

 1. Iodine reacts with chlorine to form dark brown iodine monochloride.
                                    

                                                    I2 + Cl2 → 2ICl
(a) Calculate the overall energy change for the reaction between iodine and chlorine using the bond energy values shown.

      Show your working. [3]

(b) Draw a labelled energy level diagram for the reaction between iodine and chlorine using the information in (a). [2]

[Total: 5]

2. Look this reaction.
The reaction is exothermic.

S(g) + 2F2(g)   -->  SF4(g)

(a) Complete the energy level diagram for this reaction. Include an arrow which clearly shows the energy change during the reaction.

(b) During the reaction the amount of energy given out is 780 kJ / mol.
The F–F bond energy is 160 kJ / mol.
Use this information to determine the bond energy, in kJ / mol, of one S–F bond in SF4.

.................................. kJ / mol [3]

[Total: 6]

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IGCSE CHEMICAL ENERGETICS MCQ PRACTICE (with the answer key)

IGCSE CHEMICAL ENERGETICS MCQ PRACTICE (with the answer key)

IGCSE Chemistry   12:37

1 The energy level diagram for the reaction between sodium hydrogen carbonate and dilute hydrochloric acid is shown.

     

Which row correctly describes the type of reaction and the energy of the reactants and products?

       

2. The energy level diagram for the reaction between magnesium and hydrochloric acid is shown. Which statement about the reaction is not correct?

      

A Energy is given out during the reaction.
B The products are at a lower energy level than the reactants.
C The reaction is endothermic.
D The temperature increases during the reaction.

3. The energy level diagram shows the energy of the reactants and products in a chemical reaction.

       

Which row correctly describes the energy change and the type of reaction shown?

4. Which reaction is endothermic?
A acid neutralising alkali causing a temperature increase
B adding magnesium to hydrochloric acid
C calcium carbonate decomposing when heated
D combustion of fossil fuels

5. Solid hydrated sodium carbonate was added to solid citric acid.
The mixture was stirred and the temperature recorded every 10 seconds. The results are shown on the graph:

Which row describes the reaction?

6. Which row correctly describes whether the reaction is exothermic or endothermic?

7 A metal reacts with an aqueous solution.

The graph shows the temperature before, during and after the reaction.

 

Which row describes the reaction?

8. The diagrams show four chemical reactions.

Which reaction is endothermic?

9. Limestone can be changed into slaked lime in two chemical reactions.

                  
    1 When limestone, CaCO3, is heated it decomposes into lime, CaO.

    2 Water is slowly dripped onto the cooled lime. The lime appears to expand and steam is  

      produced. Slaked lime, Ca(OH)2, is formed.

 Which row shows the correct description of each of the chemical reactions?

10. Which statements about exothermic and endothermic reactions are correct?


     1 During an exothermic reaction, heat is given out.

     2 The temperature of an endothermic reaction goes up because heat is taken in.

     3 Burning methane in the air is an exothermic reaction.

      A 1, 2        B 1 and 2 only          C 1 and 3 only         D 2 and 3 only

 11. What occurs when a fuel burns?

12. Some reactions are endothermic.
How does the temperature and energy change in an endothermic reaction?

13. Two chemical processes are described below.

● In the combustion of methane, energy is ......1...... .

● In the electrolysis of molten lead(II) bromide, energy is ......2...... .

Which words correctly complete gaps 1 and 2?

 

14. Solutions of two chemicals are mixed.

A reaction occurs and the temperature change is measured. Which statement is correct?

A  If the reaction is endothermic, the temperature decreases and energy is taken in.

B  If the reaction is endothermic, the temperature increases and energy is given out.

C  If the reaction is exothermic, the temperature decreases and energy is given out.

D  If the reaction is exothermic, the temperature increases and energy is taken in.

15. When anhydrous copper(II) sulfate is added to water a solution is formed and heat is given out

Which row correctly shows the temperature change and the type of reaction taking place?

16. When ammonium nitrate is added to water the temperature of the water decreases.
The ammonium nitrate can be recovered by evaporating the water added. Which explains these observations?
A The ammonium nitrate dissolves in the water and the process is endothermic.
B The ammonium nitrate reacts with the water and the process is endothermic.
C The ammonium nitrate dissolves in the water and the process is exothermic.
D The ammonium nitrate reacts with the water and the process is exothermic.

17. Some white anhydrous copper(II) sulfate powder is put into a beaker of water and stirred.
What would show that the process was exothermic?
A A blue solution is formed.
B The beaker feels cooler.
C The beaker feels warmer.
D The powder dissolves in the water.

18. The diagrams show the difference in energies of the reactants and products in two types of reaction.

Which diagram and which type of energy change apply to a fuel burning in air?

19. The diagram shows a match.

By striking the match, a chemical reaction takes place. Which statements about the chemical reaction are correct?

20. A diagram for the energy change during an exothermic reaction is shown

For which reactions would this be an appropriate diagram?

        1 CH4 + 2O2 → CO2 + 2H2O

        2 2H2 + O2 → 2H2O

        3 C + O2 → CO2

A none of them
B 1 and 2 only
C 2 and 3 only
D all of them

21. The diagram shows the reaction between zinc oxide and dilute hydrochloric acid.

Which terms describe the reaction?

22. Acetylene, C2H2, is a hydrocarbon. When acetylene and oxygen react, the hot flame produced can be used to weld steel. Which statement is correct?

A Acetylene and oxygen react exothermically.
B Acetylene is saturated.
C Oxygen and steel react endothermically.
D Oxygen is a gaseous fuel.

23. Which fuel needs oxygen in order to produce heat energy and which type of reaction produces the energy?

24. Some reactions are listed.

        methane + oxygen → carbon dioxide + water

        sodium + water → sodium hydroxide + hydrogen

        magnesium + hydrochloric acid → magnesium chloride + hydrogen 

Which word correctly describes all of these reactions?

A combustion

B endothermic

C exothermic

D neutralisation

25. Which is an endothermic process?

A      burning hydrogen

B      distilling petroleum

C      reacting potassium with water

D      using petrol in a motor car engine

26. The diagrams show some pieces of laboratory equipment.

Which equipment is needed to find out whether dissolving salt in water is an endothermic process?

A 1 only      B 1 and 3       C 2 and 3        D 3 only

27.  Clouds are formed when water vapour evaporates from the sea.

What is the energy change and what name is given to the type of change when water evaporates?

28. Which process is not exothermic?

29. When an acid is added to an alkali the temperature rises.

Which words describe this reaction?

A  decomposition and endothermic

B decomposition and exothermic

C  neutralisation and endothermic

D  neutralisation and exothermic

30. Which diagram shows a process in which an endothermic change is taking place?

DOWNLOAD ANSWER KEY: [click here]

IGCSE Chemistry – Chemical Energetics Worksheet

IGCSE Chemistry – Chemical Energetics Worksheet

IGCSE Chemistry   09:20

IGCSE Chemistry – Chemical Energetics

Name :

Class/# :

Day, Date :

Question 1: Multiple Choice

1. When a chemical reaction absorbs heat from the surroundings, it is called: A) Endothermic B) Exothermic C) Isothermic D) Thermogenic

Question 2: Fill in the Blanks 2. In an exothermic reaction, the surroundings __________ heat and the temperature of the surroundings __________.

Question 3: Short Answer 3. Explain the difference between endothermic and exothermic reactions, providing an example for each.

Question 4: Calculation 4. Calculate the energy change when 2 moles of methane (CH₄) are burned completely in oxygen according to the following equation: CH₄(g) + 2O₂(g) → CO₂(g) + 2H₂O(l) ΔH = -890 kJ/mol

Question 5: Application 5. Consider a reaction where 50.0 g of sodium hydroxide (NaOH) is dissolved in 200 mL of water, and the temperature of the solution increases from 25°C to 40°C. Calculate the energy change for this process. (Assume the density of water is 1 g/mL and specific heat capacity of water is 4.18 J/g°C)

Question 6: Diagram Analysis 6. Study the energy profile diagram below and answer the questions. (Insert a simple energy profile diagram with reactants and products labeled, along with activation energy.)

a) Identify the reactants and products. b) Label the activation energy on the diagram. c) Determine whether the reaction is endothermic or exothermic. d) Explain what the activation energy represents in a chemical reaction.

Question 7: Research and Analysis 7. Research an industrial process that involves an exothermic reaction. Explain the process, the reaction involved, and why the reaction being exothermic is beneficial for the industry.

Question 8: Critical Thinking 8. Discuss why it is important for scientists and engineers to understand the concept of energy changes in chemical reactions, especially in fields such as environmental science and pharmaceuticals.