Chlorine and its Compounds Questions and Answers - Chemistry Form 3 Topical Revision

Questions

1. 1. State one observation made in this experiment
   2. Identify the substances formed in the above reaction
2. Hydrogen chloride gas was passed into water as shown below:
   
   
   1. When a blue litmus paper was dropped into the resulting solution, it turned red. Give a reason for this observation
   2. What is the function of the funnel?
3. A group of compounds called chlorofluoro-carbons have a wide range of uses but they also have harmful effects on the environment. State one:-
   1. Use of chlorofluoro carbons
   2. Harmful effect of chlorofluoro carbons on the environment.
4. Water from a town in Kenya is suspected to contain chloride ions but not sulphate ions.
   Describe how the presence of the chloride ions in the water can be shown.
5. In an experiment, chlorine was passed into moist hydrogen sulphide in a boiling tube as shown below:
   
   
   1. What observation was made in the boiling tube?
   2. Write an equation of the reaction that took place in the boiling tube
   3. What precaution should be taken in carrying out this experiment? Give a reason
6. Heated iron can react with both chlorine gas and hydrogen chloride gas
   1. Write equations for the reactions
   2. Chlorine gas has no effect on dry blue litmus paper. Explain
7. The following diagram represents a set-up that can be used in the laboratory to prepare and collect a sample of chlorine gas:
   
   
   1. No gas bubbles were produced in the above experiment. Explain the observation
   2. Complete the following equation
      Cl₂O_(g) + H₂O_(l)
   3. Describe the bleaching property of chlorine water
8. Study the flow diagram below and answer the questions that follow:
   
   
   1. Name gas L ……………………………………………………………
   2. Write a balanced equation for the reaction between hydrochloric acid and manganese (IV) oxide
   3. Explain what happens to coloured petals when dropped into a solution of M
9. 
   
   1. Two reagents that can be used to prepare chlorine gas are manganese (IV) oxide and concentrated hydrochloric acid.
      1. Write an equation for the reaction
      2. Give the formula of another reagent that can be reacted with concentrated hydrochloric acid to produce chlorine gas
      3. Describe how the chlorine gas could be dried and collected in the laboratory
   2. In an experiment, dry chlorine gas was reacted with aluminium as shown in the diagram below
      
      
      1. Name substance A
      2. Write an equation for the reaction that took place in the combustion tube
      3. State the function of the calcium chloride in the set-up above
10. The figure below was set by a student to investigate the reaction between chlorine gas and hydrogen gas:
    
    
    1. Write an equation for the reaction that took place in the flask
    2. What observation was made in the flask?
    3. What precaution should be taken in carrying out the experiment?
11. In an attempt to prepare a gas, Sabulei added concentrated hydrochloric acid to Potassium manganate. The products were then passed through two wash bottles containing water and concentrated sulphuric acid
    1. Name the gas prepared…………………………………………………………………………
    2. Name the purpose of wash bottle:
       1. Containing water?
       2. Containing concentrated sulphuric acid?
12. Study the scheme below and answer the questions that follow.
    
    
    1. Write the formula of the cation present in the yellow solution F
    2. What property of chlorine is shown in Step II?
    3. Write an equation for the reaction in step III
13. 1. Name one drying agent for hydrogen Chloride
    2. State and explain the observation that would be made when hydrogen Chloride gas is bubbled into a solution of Silver nitrate
14. Carbon (IV) Oxide, methane, nitrogen (I) Oxide and trichloromethane are green house gases
    1. State one effect of an increased level of these gases to the environment
    2. Give one source from which each of the following gases is released to the environment;
       1. Nitrogen (I) Oxide
       2. Tricholomethane

Answers

1.  
   1. It catches fine or presence white fumes
   2. PCl₃ // Phosphorous Trichloride
   3. PCl₅ // Phosphorous Pentachloride
2.  
   1. - In water hydrogen chloride dissociates to form hydrogen (H⁺) and chloride (Cl^-) ions.
      - The presence of H+ ions in aqueous solution of hydrogen chloride is responsible for acidic properties which turns blue litmus paper red
   2.  – To increase the surface area for the dissolution of the gas
      - Prevent suck back (Award full 1mk for any one given)
3.  
   1. – Refrigeration ✓1
      - Maintains pressure in aerosol cans and enables sprays tobe sprayed in liquid form
   2. – They deplete the ozone layer. ✓1
      - They cause green house effect/Global warming.
4. Acidify water with nitric acid ✓½. Add aqueous lead nitrate/AgNO₃ ✓½
   Formation of a white ppt. Show presence of Cl^- white ppt of PbCl₂ or AgCl formed.
5.  
   1. Yellow solid deposit of sulphur on the wall of boiling tube
   2. H₂S _(g) + Cl_{2 (g)} → 2 HCl_(g) + S_(s)
   3. - Done in fume chamber/ open air
      - Poisonous gases
6.  
   1. 2Fe_(s) + 3Cl_2(g) → 2 FeCl_3(g)
      Fe_(s) + 2HCl_(g) → FeCl_2(g) + H_2(g)
      N.B Must be balanced
      State symbol must be correct
      Chemical symbols must be correct
   2. In the absence of moisture, chlorine cannot form the acidic solution, hence no effect on the blue litmus paper
7.  
   1. Heat is necessary * REJECT high temperature ACCEPT, BOIL or if implied
      - MnO₂ is a weak oxidizing agent.
   2. Cl₂O_(g) + H₂O(l) → 2HOCl _(aq) C.A.O
8.  
   1. Chlorine gas
   2. HCl(aq) + MnO_2(s) → MnCl_2(aq) + Cl_2(g) + 2H_2(g)
   3. The petals turn to white due to the bleaching effect of NaOCl(sodium hypochlorite)
9.  
   1.  
      1. MnO_2(s) + 4HCl_(l) → MnCl_2(aq) + 2H₂O + Cl_2(g)
         Penalize ½mk if state symbols are not correct
      2. KMnO₄ or PbO₂
      3. The Chloride gas can be dried by passing it through a wash-bottle of concentrated sulphuric acid and is then collected by downward delivery.
   2.  
      1. A- Aluminium (III) Chloride
      2. 2Al_(s) + 3Cl_2(g) → 2AlCl_3(s)
         Penalize ½mk for wrong state symbols
      3. Moles of Al used from the equation in b(ii)
         = ^0.84/₂₇ = 0.031 Moles
         Moles of Cl₂ used = 0.031 x 3 = 0.047
                                              2
         Mark consequently from the equation
10.  
    1. Cl_2(g) + H₂S_(g) → HCl_(g) + S_(s)
    2. Yellow solid particles deposited in the flask
    3. Excess chlorine and hydrogen sulphide gas should not be emitted into the atmosphere because they are pollutants /harmful ✓ ½
11.  
    1. Chlorine gas
    2.  
       1. Remove traces of hydrogen chloride gas
       2. Drying agent
12.  
    1. Fe³⁺
    2. It is an oxidizing agent
    3. 2Fe(OH)_{3 (s)} → Fe₂O_3(s) + 3H₂O_(l)
13.  
    1. Anhydrous Calcium Chloride (½mks)
    2. A white ppt is formed
       HCl gas forms Cl^- ions solution which react with silver ions to form silver Chloride which is
       insoluble OR
       HCl_(aq) + AgNO_{3 (aq)} → HNO_3(aq) + AgCl_(s)
       Cl^-_(aq) + Ag⁺_(aq) → AgCl_(s)