OCR AS Inorganic Chemistry 1 Practice Questions (PDF)

## AS SECTION 2 - INORGANIC 1 - PRACTICE QUESTIONS 1. For each of the following reactions, select from the list below, the formula of a sodium halide that would react as described. NaF NaCl NaBr NaI Each formula may be selected once, more than once or not at all. a. This sodium halide i...

## AS SECTION 2 - INORGANIC 1 - PRACTICE QUESTIONS 1. For each of the following reactions, select from the list below, the formula of a sodium halide that would react as described. NaF NaCl NaBr NaI Each formula may be selected once, more than once or not at all. a. This sodium halide is a white solid that reacts with concentrated sulfuric acid to give a brown gas. Formula of sodium halide: **NaBr** (1 mark) b. When a solution of this sodium halide is mixed with silver nitrate solution, no precipitate is formed. Formula of sodium halide: **NaF** (1 mark) c. When this solid sodium halide reacts with concentrated sulfuric acid, the reaction mixture remains white and steamy fumes are given off. Formula of sodium halide: **NaCl** (1 mark) d. A colorless aqueous solution of this sodium halide reacts with orange bromine water to give a dark brown solution. Formula of sodium halide: **NaI** (1 mark) 2. There are many uses for Group 2 metals and their compounds. a. State a medical use of barium sulfate. State why this use of barium sulfate is safe, given that solutions containing barium ions are poisonous. Use: **Barium sulfate is used as a contrast medium in X-rays of the digestive system.** Why this use is safe: **Barium sulfate is insoluble and therefore does not dissolve in the body, so it is safe to ingest.** [2 marks] b. Magnesium hydroxide is used in antacid preparations to neutralize excess stomach acid Write an equation for the reaction of magnesium hydroxide with hydrochloric acid. **Mg(OH)2 + 2HCl --> MgCl2 + 2H2O** [1 mark] c. Solutions of barium hydroxide are used in the titration of weak acids. State why magnesium hydroxide solution could not be used for this purpose. **Magnesium hydroxide is a weak base, so it would not be suitable for titrating weak acids. ** [1 mark] d. Magnesium metal is used to make titanium from titanium(IV) chloride. Write an equation for this reaction of magnesium with titanium (IV) chloride. **TiCl4 + 2Mg --> Ti + 2MgCl2** [1 mark] e. Magnesium burns with a bright white light and is used in flares and fireworks Use your knowledge of the reactions of Group 2 metals with water to explain why water should not be used to put out a fire in which magnesium metal is burning. **Magnesium reacts vigorously with water to produce hydrogen gas. This reaction would add fuel to the fire and make it more difficult to extinguish.** [2 marks] 3. This question is about Group 7 chemistry. a. Sea water is a major source of iodine. The iodine extracted from sea water is impure. It is purified in a two-stage process. Stage 1: I2 + 2H2O + SO2 --> 2HI + H2SO4 Stage 2: 2HI + Cl2 --> I2 + 2HCl (i) State the initial oxidation state and the final oxidation state of sulfur in Stage 1. Oxidation state of S in SO2: **+4** Oxidation state of S in H2SO4: **+6** [2 marks] (ii) State, in terms of electrons, what has happened to chlorine in Stage 2 **Each chlorine atom has gained one electron.** [1 mark] b. When concentrated sulfuric acid is added to potassium iodide, iodine is formed in the following redox equations. KI + H2SO4 --> KHSO4 + I2 + S + ......H2O 8KI + 9H2SO4 --> 8KHSO4 + 4I2 + H2S + 4H2O (i) Balance the equation for the reaction that forms sulfur. **2KI + 3H2SO4 --> K2SO4 + I2 + S + 3H2O** [1 mark] (ii) Deduce the half-equation for the formation of iodine from iodide ions. **2I- --> I2 + 2e-** [1 mark] (iii) Deduce the half-equation for the formation of hydrogen sulfide from concentrated sulfuric acid. **H2SO4 + 8e- + 8H+ --> H2S + 4H2O** [1 mark] c. A yellow precipitate is formed when silver nitrate solution, acidified with dilute nitric acid, is added to an aqueous solution containing iodide ions. (i) Write the simplest ionic equation for the formation of the yellow precipitate. **Ag+ + I- --> AgI(s)** [1 mark] (ii) State what is observed when concentrated ammonia solution is added to this yellow precipitate. **The yellow precipitate dissolves to form a colorless solution.** [1 mark] (iii) State why the silver nitrate solution is acidified when testing for iodide ions. **To prevent the formation of a precipitate of silver hydroxide.** [1 mark] (iv) Explain why dilute hydrochloric acid is not used to acidify the silver nitrate solution in this test for iodide ions. **Hydrochloric acid would react with the iodide ions to form iodine, which would give a false positive result.** [1 mark] d. Chlorine is toxic to humans. This toxicity does not prevent the large-scale use of chlorine in water treatment. (i) Give one reason why water is treated with chlorine. **To kill bacteria and other harmful microorganisms.** [1 mark] (ii) Explain why the toxicity of chlorine does not prevent this use. **Chlorine is present in very low concentrations in treated water, so it is not harmful to humans.** [1 mark] (iii) Write an equation for the reaction of chlorine with cold water. **Cl2 + H2O --> HCl + HOCl** [1 mark] e. Give the formulas of the two different chlorine-containing compounds that are formed when chlorine reacts with cold, dilute, aqueous sodium hydroxide. Formula 1: **NaCl** Formula 2: **NaOCl** [1 mark] 4. (a) The diagram below shows the melting points of some of the elements in Period 3. (i) On the diagram, use crosses to mark the approximate positions of the melting points for the elements silicon, chlorine and argon. Complete the diagram by joining the crosses. **I am unable to complete this task, as I am a text-based format, but I can describe what the diagram should look like. The melting points are expected to appear in the following order from lowest to highest: argon, chlorine, silicon, sodium, magnesium, aluminum, phosphorus, sulfur.** (ii) By referring to its structure and bonding, explain your choice of position for the melting point of silicon **Silicon has a giant covalent structure, meaning that there are strong covalent bonds between all the silicon atoms. These strong bonds require a lot of energy to break, so silicon has a high melting point.** (iii) Explain why the melting point of sulfur, S8, is higher than that of phosphorus, P4. **Sulfur exists as S8 molecules, which are held together by strong van der Waals forces. Phosphorus exists as P4 molecules, which have weaker van der Waals forces. The stronger van der Waals forces in sulfur require more energy to break, so sulfur has a higher melting point.** (8 marks) (b) State and explain the trend in melting point of the Group II elements Ca-Ba Trend: **The melting point of the Group II elements Ca-Ba increases as you go down the group.** Explanation: **The metallic bonding in the Group II elements gets stronger as you go down the group The atoms get larger, so the outer electrons are further away from the nucleus and are less strongly attracted. This means that the outer electrons are more easily delocalized, which leads to stronger metallic bonding. Stronger metallic bonding requires more energy to break, so the melting point increases.** (3 marks)