Chemistry Paper 2 Questions and Answers - Eagle II Joint 2021 Mock Exams

INSTRUCTIONS TO THE CANDIDATES:

• Answer all the questions.
• All working must be clearly shown where necessary.
• Mathematical tables and electronic calculators can be used.

1. Use the table below to answer the questions that follow. (The letters do not represent the actual symbols of the elements).
   

   Element	Atomic Number	Melting point °
   A   B   C   D   E	11     13     14     17     19	97.8      660     1410      − 101       63.7

   1. Write the electronic arrangement for the ions formed by element B and D. [2mks]
   2. Select an element which is:
      1. A non-conductor of electricity [1mk]
      2. The most reactive non-metal [1mk]
   3. To which period of the periodic table does element E belong? [1mk]
   4. Element E losses its outermost electron more readily than A. Explain. [1mk]
   5. Use dots (.) and crosses (x) to represent the valence electrons and show the bonding in the compound formed between element C and D. [1mk]
   6. Explain why the melting point of element B is higher than that of element A [1mk]
   7. Write an equation for the reaction that takes place between element A and water. [1mk]
2.  
   1. The set-up below was used to collect gas F, produced by the reaction between water and calcium metal.
      1. Name gas F [1mk]
      2. At the end of the experiment the solution in the beaker was found to be a weak base. Explain why the solution is a weak base. [1mk]
      3. Give one laboratory use of the solution formed in the beaker. [1mk]
   2. The scheme below shows some reaction starting with calcium oxide. Study it and answer the questions that follow.
                
      1. Name the reagent used in step 2 and 4 [1mk]
      2. Write an equation for the reaction in step 3 [1mk]
      3. Describe how a solid sample of anhydrous calcium sulphate is obtained in step 5 [3mks]
3. The figure below is a flow chart showing the process that occurs in the manufacture of nitric (V) acid.
             
   1. Name substance P, Q, R and S.  (4 mks)
   2. To obtain substance R, ammonia is heated at 9000C in the presence of air and a catalyst.
      The product is then cooled in the heat exchanger and mixed with more air.
      1. Name the catalyst for the reaction (1mk)
      2. Write the equation for the reaction described (1mk)
   3. When ammonia is reacted with nitric (V) acid, it produces a nitrogenous fertilizer.
      1. Calculate the percentage of nitrogen in the fertilizer obtained. (N=14,H=1,O=16) (2mks)
      2. State one problem associated with the use of nitrogenous fertilizers. (1mk)
4. The diagram in Figure below was used to prepare hydrogen chloride gas which was then passed over heated iron powder.
           
   1. Give a pair of reagents that will produce hydrogen chloride gas in flask A. (2mks)
   2. Name the substance in flask B. (1mk)
   3. State the observation made in the combustion tube after the reaction is complete. (1mk)
   4. Write an equation for the reaction in the combustion tube. (1mk)
   5. Describe a chemical test for hydrogen chloride gas. (1mk)
   6. Identify the gas that burns at the jet and explain why the gas is burned.  (1mk)
   7. Give reasons why excess hydrogen chloride gas is dissolved using the funnel arrangement. (1mk)
5.  
   1. Define the following:
      1. Empirical formula. (1mk)
      2. Molecular formula. (1mk)
   2. A major textile dye manufacturer developed a new yellow dye. The dye has a percent composition of 75.95% Carbon, 17.72% Nitrogen, and 6.33% Hydrogen by mass. Determine;
      1. The empirical formula of the dye. (C=12, H=1, N=14) (3mks)
      2. The molecular formula of the dye, if it has a molar mass of about 237 g/mol. (C=12, H=1, N=14) (2mks)
6.  
   1.  
      1. Define the term fuel [1mk]
      2. Determine the heating value of ethanol  [2mks]
         (C = 12, H = 1, O = 16) 
         (ΔH_c(C₂H₅OH) = -1368KJ/mol)
   2. The diagram below represents a set-up that was used to determine the enthalpy of combustion of ethanol.
      The following results were obtained:
      Volume of water = 500cm³
      Initial temperature of water = 25^oC
      Final temperature of water = 38^oC
      Mass of ethanol + lamp before heating = 120.5g
      Mass of ethanol + lamp after heating = 119.5g
      1. Calculate the heat evolved
         (Specific heat capacity = 4.2jg-k-, density of water = 1g/cm³) [2mks]
      2. Determine the molar heat of combustion of ethanol (C = 12, H = 1, O = 16) [3mks]
      3. Write the thermochemical equation for the reaction. [1mk]
      4. The theoretical value for the molar enthalpy of combustion of ethanol is -1368kJ/mol
         Why is the value calculated from the experimental results different from this? [1mk]
      5. Define the term molar heat of combustion [1mk]
7.  
   1.  
      1. Give the systematic name of the following compound.  [1mk]
         CH₃CH₂COOCH₃ 
      2. Draw the structure of 2-methyl but -1, 3-diene [1mk]
   2. The scheme below shows the reactions of organic compounds, study it and answer the questions that follow.
            
      1. Name the process in step 1 [1mk]
      2. State the condition for the process in step 2 [1mk]
      3. Write the equation for the process in step 4 [1mk]
      4. Name the process taking place in step 3 [1mk]
      5. Name the organic compound A the product of step (IV) [1mk]
      6. Given that the relative formula mass of the product of step (VI) is 56000. Determine the value of n. (C=12, H=1) [2mks]
   3. The flow chart below is a summary of the process involved during preparation of a detergent.
             
      1. Name the reagent in process 1 [1mk]
      2. Draw the structure of P; Give its name [2mks]
      3. State one advantage of detergent P   over COO^-Na⁺ [1mk]
8.  
   1. Define the term solubility [1mk]
   2. Experiments were done to determine the solubility of two salts X and Y in water at different temperatures. The following results were obtained:
      

      Temperature (°C)	Solubility in g/100g of water
      	X	Y
      0     10     20     30     40     50     60     70     80	14.0       17.5       21.0       25.0       28.5       33.0       40.0       47.0       55.0	25.0       27.0       30.0       32.5       35.0        37.5        40.0         42.5         45.0

      1. On the same axis plot the solubility corves for salts X and Y [5mks]
      2. Determine the solubility of salt Y at 45oC [1mk]
      3. At what temperature is the solubilities of the two salts equal [1mk]
      4. 80g of a saturated solution of salt X was cooled from 75°C to 15°C, determine the mass of salt X that crystallized out [3mks]
      5. A mixture containing 20g of X and 40g of Y in 100g of water at 80°C was cooled to 30°C. Identify the salt that crystallized out. Calculate the mass of the salt that crystallized. [3mks]

MARKING SCHEME

1.  
   1. B – 2.8 √               
      D – 2.8.8√  (2mks)
   2.  
      1. D √    (1mk)                 
      2. D√ (1mk)
   3. Period 4√ (1mk)
   4. E – has a bigger/greater/larger atomic radius√ hence loses its outermost electrons easily. √ (1mk)
   5.  
      √(1mk)
   6. B has more delocalized electrons√1/2 than A hence has stronger metallic bond. √1/2 (1mk)
      OR B has smaller atomic radius√1/2 hence stronger metallic bond√1/2
   7.  2A_(s)   +   H₂O_(l)         2AOH_(aq)  +  H_2(g)  (1mk) √
      (Accept if actual symbols used, award 0 if not balanced, penalize half mark for wrong state symbol)
2.  
   1.  
      1. Hydrogen gas (1mk) (strictly the name)
      2. Ca (OH)₂   slightly soluble in water, √  only few OH^- are produced√½ in  solution.     (1mk)
      3. It is used for testing presence of CO₂. √          (1mk)
         Prepare ammonia √ (any one)
   2.  
      1.  
         • Step 2  - carbon (IV) oxide√½ (½mk)
         • Step 4 – Dilute HCL√1/2  (½ mk)
      2. Ca (HCO₃)_2(aq)     CaCO_3(s)     +   CO_2(g)   +   H₂O_(l)     (1mk)
      3.  
         • Add an aqueous solution of sulphuric (VI) acid/Na₂SO₄/K₂SO₄    (1mk)
         • Filter to obtain CaSO₄  √   
         • Wash with distilled water√ and dry between filter papers√   
3.  
   1.  
      • P Hydrogen/nitrogen    1mk
      • Q Nitrogen /hydrogen  1mk
      • R Nitrogen (IV) oxide    1mk
      • S Water      1mk
   2.  
      1. Platinum – rhodium    1mk
      2. 4NH_3(g)  +  5O_2(g)    4NO_(g)  +  6H₂O_(g)  √   
         2NO(g)   +  O_2(g)        2NO_2(g)      √
   3.  
      1. NH₄NO₃√½ (REM = 80)  √½
         ²⁸/₈₀  x 100 √½ = 35% √½
      2.  
         • Lowers soil Ph
         • Increase soil acidity
         • Causes euthrophication
         • Pollution of water
           (any one)
4.  
   1.  
      • solid sodium chloride/rock salt
      • Concentrated Sulphur (VI) acid
   2. Concentrated Sulphur (VI) acid(penalize formula)
   3. Grey iron powder turns to green iron (II) chloride (acc. Green solid formed)
   4. HCl_(g)  +  Fe_(s)        FeCl_2(s)    +  H_2(g)  1mk
   5. When in contact with ammonia gas, dense white fumes of ammonium chloride are formed  (1mk)
   6. hydrogen gas √½
      • Mixture of hydrogen and air burns explosively√½
   7. to prevent sucking back in increasing surface area for dissolution
5.  
   1.  
      1. formula showing the simplest whole ratio in which atoms combine to form compound
      2. Formula showing the actual number of each kind of atoms present in molecule of the compound
   2.  
      1.   
         
      2. n(79)=237√½
         237 = 3 √½
          79
         C₁₅H₁₅√1
6.  
   1.  
      1. A substance that burns in air to produce useful energy      (1mk)
      2. CH₃CH₂OH
         RFM  = 46√½
         = 1368  (√½)      =29.74 kJ/g     (√1mk)
               46
   2.  
      1. ΔH = MCDJ
               = 500 x 4.2 x 13 (1mk)
                = 27,3005
                = 27.3Kj  1mk
         (penalize half mark for wrong units)
      2. Mass of ethanol
         120.5-119.5=1g (√ 1mk)
         1g – 27.3kJ
         46g – 46 x 27.3   (  √ 1mk)
                        1
         = 1255 .8Jk
         = -1255.8kJ/mol   (1mk)(penalize half mark for missing –ve sign Penalize fully for wrong units)
      3. CH₃CH₂OH(g) +  3O_2(g)    2CO_2g  +  3H₂OΔH = -1255.8 kJj/mol   (√ 1mk)
      4. heat loss to the surrounding (1mk)
         
         • Error in measurements of volume and temperature (experiment errors)
      5. Heat change that occur when one mole of a substance burns completely in oxygen. (√ 1mk)
7.  
   1.  
      1. Methylpropanoate  (√ 1mk)
      2.   
         
   2.  
      1. Photosynthesis (√ 1mk)
      2. yeast (√ 1mk)
      3. 2CH₃CH₂OH  + 2Na   2CH₃CH₂ONa  +  H₂  (√ 1mk)
      4. Oxidation  (√ 1mk)
      5. sodium ethoxide  (√ 1mk)
      6. ?  - (C₂H₄)  = 56000
         28n = 56000√
         ?n   = 2000√ (2mks)
   3.  
      1. concentrated sulphuric acid  (√ 1mk)
      2.  
          (√ 1mk)
         • Sodium alkylbenzene sulphanoate (√ 1mk)
      3. Does not form scum with hard water (√ 1mk)
8.  
   1. The maximum mass of a solute that can dissolve in 100g of solvent (water) at a particular temperature to form saturated solution.  (√ 1mk)
   2.  
      2. 36.5g/100g of water   ± 1 (1mk)(Read from correct curve)
      3. 60°C      ± 1  (1mk)
      4.  51.5   x 80   –    28.5  x 80  =  9.452g  (√ 1mk)
         151.5 (√1mk)    128.5 (√ 1mk)
      5. Solubility of g/100g of water at
         

         Salt	30°C	80°C
         X	25	55
         Y	32.5	45

         Crystal of y (√ 1mk)
         40 − 32.5 = 7.5g (√ 1mk)