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MnO4 (aq) + H+(aq) + H2S(g) → Mn2+(aq) + S(s) + H2O(ℓ) 9.1 Define reduction in terms of oxidation numbers. (2) 9.2 Determine the oxidation number of manganese in the permanganate ion. (1) 9.3 Write down the FORMULA of the substance that undergoes oxidation. (1) 9.4 Explain the answer to QUESTION 9.3 in terms of … Read more

Ammonia can readily dissolve in water according to the equation below: 8.1 Explain why a hydroxide ion is regarded as a Lowry-Brønsted base. (2) 8.2 Identify the type of bond responsible for the formation of the ammonium ion inthe above equation. (1) 8.3 Write a balanced equation to show how the ampholyte in the above … Read more

The following reaction between ammonia and oxygen takes place in a closed systemat constant pressure and temperature: 4NH3(g) + 5O2(g) → 4NO(g) + 6H2O(g) 7.1 Define the term activation energy. (2) 7.2 Give a reason why this reaction is exothermic. (1) 7.3 Calculate the heat of reaction. (3) 7.4 Redraw the graph and indicate with … Read more

6.1 In an experiment, a learner added 1,5 g of sodium carbonate (Na2CO3) tohydrochloric acid (HCℓ). A volume of 306 cm3 of carbon dioxide gas wasformed and collected under standard pressure at room temperature. Take themolar gas volume at room temperature (Vm) as 24,45 dm3. The unbalanced equation for the reaction is: Na2CO3(s) + HCℓ(aq) … Read more

A balloon is filled with 160 g of argon gas (Ar). The pressure of the gas is 120 kPa ata temperature of 15 ºC. 5.1 Calculate the volume of the balloon. (4) 5.2 The temperature of the gas is now increased BY 20 ºC and the initial pressureis doubled. Calculate the new volume of the … Read more

A certain amount of gas is sealed in a container of which the volume can change.The relationship between the pressure and volume of the gas at 20 ºC is investigated.The results of the experiment are given in the table below. 4.1 Name the gas law that is represented by the results of the experiment. (1) … Read more

The reaction below is used in the Haber process to manufacture ammonia N2(g) + 3H2(g) → 2NH3(g) The boiling points of the substances in the reaction are as follows: 3.1 Refer to the intermolecular forces and explain the difference in boiling pointbetween NH3 and N2. (3) 3.2 Write down the FORMULA of the substance in … Read more

Hydrogen cyanide (HCN) is a very poisonous compound used in the manufacturing ofplastics, mining of gold and as a poison. 2.1 Define the term chemical bond. (2) 2.2 Draw Lewis structures for: 2.2.1 HCN (2) 2.2.2 H2O (2) 2.3 What is the shape of the HCN molecule? (1) 2.4 Calculate the electronegativity difference for the … Read more

Various options are provided as possible answers to the following questions.Choose the answer and write only the letter (A–D) next to the question numbers(1.1 to 1.10) in the ANSWER BOOK, e.g. 1.11 E. 1.1 The tendency of an atom to attract the bonding pair of electrons is knownas … A electron affinity.B electronegativity.C polarity.D activation … Read more