Chemistry Trial Exams Paper 2 Questions - Alliance Boys High School Mock December 2020

INSTRUCTION TO CANDIDATES

• Write your name and Index number in the spaces provided above.
• Answer all questions in the spaces provided
• Mathematical tables and electronic calculators may be used.
• All working must be clearly shown where necessary

For Examiner's Use Only

QUESTIONS

1.                                  
   1.                        
      1. Define heating value of a fuel. (1mk)
      2. Give two reasons why wood and charcoal are chosen for domestic heating, (2mks)
   2. The diagram below shows the set-up of the apparatus by a student to determine the enthalpy change of combustion of ethanol. The heat produced by burning fuel warms known mass of known.
      
      Results.
      Volume of water in the beaker = 500cm
      Initial temperature of water = 12°C
      Final temperature of water = 31.5°C
      Mass of ethanol burnt = 1.50g
      Density of water = 1 g/cm
      Specific heat capacity of water = 4.2 kJ kg-1 k-1
      1. Define standard heat of combustion. (1mk)
      2. Calculate the heat required to raise the temperature of water from 12°C to 31.5°C (2mks)
      3. Find the molar enthalpy of combustion of ethanol. (2mks)
         (C-12, 0=16, H=1)
      4. Draw an energy level diagram for the combustion of ethanol. (2mks)
2.                                                            
   1. Chlorine gas dissolves in water to form liquid P. When liquid P is exposed to the sunlight a colourless gas Q and a colourless solution Rare formed.
      1. Name :
         1. Liquid P (1mk)
         2. Gas Q (1mk)
      2. Write a chemical equation leading to formation of gas Q (1mk)
      3. Compare the pH value of solution P with that of colourless solution R. Explain your answer (2mks)
   2. Study the diagram below and answer the questions that follow;
      
      
      1. Write chemical equation for the formation of bleaching powder (1mk)
      2. When exposed to the atmosphere, bleaching powder smells strongly of chlorine. Explain (1mk)
      3. Name the yellow solid (1mk)
      4. State and explain the observation made when chlorine gas is bubbled in potassium bromide solution (2mks)
      5. Name two uses of chlorine (2mks)
3.                                    
   1. Draw the structures of the following compounds;
      1. 3-bromo-2-methylpent-2-ene (1mk)
      2. 2,2-dimethylbutane (1mk)
   2. Study the flow chart below and answer the questions that follow.
      
      
      1. State one condition necessary for step 1 to occur. (1mk)
      2. Identify substances; (2mks)
         1. A ..........
         2. B......
      3.        
      4. Write chemical equation taking place in step IV (1mk)
      5. State the alternative method of preparing ethanol. (1mk)
      6. Ethanoic acid has higher melting and boiling point than ethanol. Explain. (1mk)
   3. Nylon is a polymer formed when two monomers combine with release of hydrogen and chlorine gas molecules. Use the structure of the nylon shown below to answer the questions that follow.
      
      
      1. Name the type of polymerization (1mk)
      2. Draw the structures of the two monomers unit of nylon (2mks)
4. The grid below shows part of the periodic table. Use it to answer the questions that follow. (The letters are not the actual symbols of the elements)
   
   
   1.  Identify the element representing the largest atom. Explain. (2mks)
   2. Explain why atom of element W is heavier than that of element V (1mk)
   3. Given that the atomic mass of W is 40, write down the composition of its nucleus. (2mks)
   4. What name is given to the group of elements in which element U belongs? (1mk)
   5. Write an equation for the decomposition of nitrate of element P. (1mk)
   6. Using dots (.) and crosses (x) show bonds formed when R and U reacts (2mks)
   7. When 3 litres of chlorine gas were completely reacted with element Q, 11.88g of the product was formed. Determine the relative atomic mass of element Q. (Atomic mass of chlorine = 35.5, molar gas volume 24 litres) (3mks)
5.                              
   1. The chart below shows some reactions starting with ammonia. Study it answer the questions that follow.
      
      
      1. Name the catalyst used in stepI (1mk)
      2. Write down the equation for the reaction that requires the catalyst in step I. (1mk)
      3. Write down the formula of the complex ion present in solution C. (1mk)
      4. What property of concentrated nitric (V) acid is shown by the reaction in step II ? (1mk)
      5. Name process taking place in step (IV) (1mk)
   2. 1.8 litres of ammonia gas was bubbled through excess dilute nitric (V) acid at room temperature and pressure. Determine the mass of the product formed. (Molar gas volume = 24.0dm³, N = 14,0 = 16, H = 1) (3mks)
   3. Consider the reaction represented by the equation:
      N₂(g) + O₂(g) ⇄ 2NO(g)     △H = +1259kJ 
      Explain the effects nitrogen (II) oxide on increase in temperature (2mks)
6.                                          
   1. The set up below shows the reagents that can form hydrogen gas in a laboratory
      1. Complete the diagram to show how a dry sample of hydrogen gas can be collected. (3mks)
         
      2. Write the chemical equation for above reaction. (1mk)
      3. Why is it not advisable to use calcium in this method to prepare hydrogen? (2mks)
      4. Hydrogen gas is used in hydrogenation of oils. What do you understand by the term hydrogenation? (1mk)
   2. In an experiment to study the rate of reaction a 10cm length of magnesium ribbon was reacted with 50cm³ of IM hydrochloric acid. The table below gives the data that was collected

      Time(sec)	0	10	20	30	40	50	60	70	80	90
      Volume of hydrogen(cm3)	0	60	90	105	112	116	118	120	120	120

      1. Plot a graph of volume of hydrogen against time. (3mks)
         
      2. From the graph find
         1. The rate of reaction when time is 35 seconds. (2mks)
         2. Sketch on the diagram the curve you would obtain if the reaction is repeated using 0.5M HCL. Label this curve 0.5M HCI. (1mk)
7.                                
   1. Study the flow chart below on extraction of copper and answer the questions that follow.
      
      
      1.  Name the chief copper ore used for the extraction of copper. (1mk)
      2. The amount of copper in the copper ore is very small. State the method used to concentrate the ore in chamber A. (1mk)
      3. Identify substance B and state its function. (2mks)
      4. Write an equation for the reaction that takes place in the roaster. (1mk)
      5. The blister copper obtained is impure. With the aid of a diagram, describe how it can be purified. (2mks)
   2. Bronze is an alloy of copper and another metal.
      f. Give the chemical symbol of the other metal. (1mk)
      g. State one use of bronze. (1mk)
   3. During purification of copper by electrolysis, 1.48g of copper were deposited when a current was passed through aqueous copper (II) sulphate for two and half hours. Calculate the amount of electricity that was passed. (Cu-63.5, 1 Faraday 96500C) (3mks)