Chemistry Paper 2 Questions and Answers - Maranda Pre-Mock Examinations 2022

QUESTIONS

1.      
   1. In an experiment to determine the percentage of oxygen in air, the apparatus below were set up. Study the set up and the information provided to answer the questions that follow.
      
      A 500cm³ measuring cylinder K was filled with water and assembled for gas collection. Copper turnings were heated red hot and water was slowly passed into 500cm³ flask H until it reached the 500cm³ mark. A colourless gas was collected in K.
      
      1. What was the purpose of passing water into flask H? (1 mark)
      2. What observations were made in the tube I?  (1 mark)
      3. Name one of the gases that is likely to be found in J. (1 mark)
      4. What was the volume of the gas collected in the measuring cylinder at the end of the experiment?(1 mark)
      5. Calculate the percentage of oxygen in air using the above results.(2 marks)
   2. Study the diagram below and answer the questions that follow.
      
      
      1. Give one observation made in the combustion tube after some time. (1 mark)
      2. Write an equation for the formation of the colourless liquid Y. (1 mark)
      3. What was the aim of the above experiment as demonstrated in the combustion tube? Explain. (2 marks)
2. Use the information below to answer the questions that follow. The letters are not the actual symbols of the elements.
   

   Element	Atomic No.	M.PºC	B.PºC	Ionic radius (nm)
   P	11	98	890	0.095
   Q	12	650	1110	0.065
   R	12	660	2470	0.050
   S	14	1410	2360	0.041
   T	15	44.2 & 590	280	0.034
   U	16	113 & 119	445	0.184
   V	17	-101	-35	0.181
   W	18	-189	-186	-

   1.    
      1. Write the electronic configuration of the atoms represented by letters T and W. (1 mark)
      2. State the nature of the oxides of the elements represented by Q and U. (2 marks)
   2. Why does the elements represented by the letters T and U have two values of melting points? (1 mark)
   3. Explain the following observations in terms of structure and bonding,
      
      1. There is an increase in boiling point from P to R. (2 marks)
      2. Element S has a high boiling point. (2 marks)
      3. There is a decrease in boiling points from U to W. (2 marks)
   4.    
      1. Compare the atomic radius of U and V. Explain. (1 mark)
      2. Why is there no ionic radius for W reported in the table? (1 mark)
3.    
   1. The solubilities of potassium nitrate and potassium bromide at different temperatures wa determined. The following data was obtained.
      

      Temperature °C	0	10	20	30	40	50	60	70	80
      Solubility g/100g H2O	5	15	26	43	61	83	105	135	165
      	50	55	60	65	70	77	85	90	95

      1. Draw solubility curves for both salts on the same axis. (3 marks)
         
      2. From your graph, determine the solubility of each salt at 65°C? (1 mark)
      3. 100g of a saturated solution of potassium nitrate at 70°C was cooled to 20°C. What mass of the crystals will be crystallized? (2 marks)
   2. Study the flow chart below and answer the questions that follow.
      
      
      1. Write an equation for the formation of solid A and gas B. (1 mark)
      2. Name: Solution C
         Solution D (1 mark)
   3. Write the formula of the complex ion in solution E. (1 mark)
4. Study the flow chart below and answer the questions that follow.
   
   
   1. Name substance. (3 marks)
      X, Q, R
   2. Write down an equation for the reaction represented by step III. (1 mark)
   3. What are the conditions and reagent required for steps?
      
      1. I - Reagent
         Condition (2 marks)
      2. IV - Reagent - ......
         Condition (2 marks)
   4. Name the process represented by:(4 marks)
      I, II, IV, V
5.    
   1. Study the scheme below and answer the questions that follow
      
      
      1. Identify substances. (3 marks)
      2. State the catalyst necessary for;
         Step I -
         Step II -
      3. Write an equation for the reaction taking place in step II. (1 mark)
      4. Write two balanced chemical equations for the reaction between chlorine gas and;
         1. Hot and concentrated sodium hydroxide, (1 mark)
         2. Dilute and cold sodium hydroxide. (1 mark)
   2. The diagram below shows an experiment in which the Lead (II) nitrate crystals are heated.
      
      1. Name; (2 marks)
         
         1. Liquid P -
         2. Gas Y
      2. Write a balanced chemical equation for the decomposition of Lead (II) nitrate, (1 mark)
      3. Explain how you can distinguish between nitrogen (II)oxide and nitrogen (1) oxide. (2 marks)
6.      
   1.    
      1. State Hess' Law (1 mark)
      2. Use the equations given below to answer the questions that follow.
         C₂H_6(g) + ⁷/₂ O_2(g) → 2CO_2(g) + 3H₂O_(I)   ΔH = -1560 kJ/mole
         C(s) + O_2(g) → CO_2(g)   ΔH = - 394 kJ/mole
         H_2(g) + ½O_2(g)→ H₂O_(g)  ΔH = - 286 kJ/mole
         
         1. Draw an energy cycle diagram that links the enthalpy of formation of ethane to combustion of carbon, hydrogen and ethane. (1 mark)
         2. Determine the enthalpy of formation of ethane (2 marks)
            
   2. The diagram below shows the set-up of the apparatus used by a student to determine the enthalpy change of combustion of ethanol. The heat produced by burning fuel warms a known mass of water.
      
      Results
      Volume of water in the beaker 500cm³
      Initial temperature of water 12°C
      Final temperature of water = 31.5°C
      Mass of ethanol burnt = 1.50g
      Density of water = 1 g/cm³
      Specific heat capacity= 4.2 Jg^-1K^-1
      1. Calculate the heat required to raise the temperature of the water from 12°C to 31.5°C. (2 marks)
      2. Find the molar enthalpy of combustion of ethanol.
         (C = 12, H = 1,0 = 16)
      3. An accurate value for AHC of ethanol is -1368 kJmoll. State two sources of errors for the low figure obtained (2 marks)
      4. Draw an energy level diagram for the combustion of ethanol. (2 marks)
      5. Calculate the heating value of ethanol from the above experiment.
         (C = 12, H = 1,0 = 16)
7.      
   1. The diagram below represents a setun of aparatus used in the electrolysis of lead (1) bromide
      
      
      1. Name electrodes C and D (1 mark)
      2. State and explain the observation made at electrode D (2 marks)
      3. Write the ionic equation for the reaction at electrode C (1 mark)
      4. State two applications of electrolysis (2 marks)
   2. The table below gives some properties of substances A, B, C, and D. Study it and answer the questions that follow.
      

      Substance	Electrical Conductivity		Melting Point (°C)	Boiling Point(°C)
      	Solid	Molten
      A	Does not conduct	Conducts	801	1420
      B	Conducts	Conducts	650	1107
      C	Does not conduct	Does not conduct	1700	2200
      D	Does not conduct	Does not conduct	113	440

      1. Which particles are responsible for conductivity in substances: (2 marks)
      2. Which substance is likely to be silicon (IV) oxide? Explain.(2 marks) 

MARKING SCHEME

1.    
   1.     
      1. to displace air in flas H over hot copper turnings
      2. Brown copper metal changes to black copper (II) oxide
      3. nitrogen/ carbon (IV) oxide/ Argon/ Neon
      4. 390 - 400cm³
      5. 500 - Value above x 100%
            500
   2.      
      1. black copper(II) oxide changes to brown copper metal
      2. H₂O(g) → H₂O// H₂+ O₂ → 2H₂O
      3. to determine/ investigate the reducing property of hydrogen. Hygrogen is above copper in the reactivity series
2.    
   1.      
      1. T - 2.8.5 
         W - 2.8.8
      2. Q - Basic 
         U - Acidic
   2. Exhibit allotropy
   3.      
      1. increase in number of decolorised electrons/ Decrease in atomic radius which in turn increases the strength of metalic bond
      2. A aroms are held by strong covalent bonds within the giant covalent/ atomic structure
      3. U,V,W have simple molecular structures in which the molecules are held by weak van der forces. There is decrease in the strength of van der waals
   4.    
      1. V has a smaller atomic radius than U. V has more protons leading to excess effective nuclear charge
      2. stable; neither gains nor loses electrons / does not ionize
3.    
   1.    
      1.    
         
      2. KNO₃ 119g/ 100g of water 1
         KBr 87g/100g of water 1
      3. At 70ºC
         If 235g of solution contain 135g of salt
         100g →100 x 135 = 57.4468g(57.45g)
                          235 
         At 20ºC
         If 126g of solution → 26g of salt
         100g → 100 x 26 = 20.63
                          126
         Mass crystallised = 57.4468 = 36.81g
   2.    
      1. CuCO_3(s) →heat→ CuO_(s) + CO_2(g)
      2. C - Copper(II)chloride/ CuCl₂
         D - Copper (II) Hydroxide / Cu(OH)₂
   3. [Cu(NH₂)₄]²⁺
4.    
   1. X - Sodium ethanate
      Q - Sodium ethoxide
      R - i - iodethane
   2. CH₃COONa(s) + NaOH(aq)→CH_4(g) + Na₂CO_3(s)
   3.      
      1. Reagent - Propanol
         Condition - Warming/heat
         Conc H₂SO_4(I)
      2. Reagent -  H+IK₂CrO₇// KMnO_4(aq)
         Condition - Heat// High temperature/ warm
   4. I - esterification
      II - Halogenation/chlorination
      IV - Oxidation
      V - Dehydration
5.      
   1.      
      1. A - Hydrogen
         B - Nitrogen
         D - Nitrogen(II) oxide
      2. Finely divided iron
         Platinum - Rhodium / platinum
      3. 4NH_3(g) + 5O_2(g) 4NO(g) + 6H₂O(g)
      4.      
         1. 6NaOH(aq) + 3Cl(g) + 3Cl_2(g) → NaClO_3(aq) + 5NaCl(aq) + 3H₂O
         2. 2NaOH(aq) + Cl_2(g) → NaClO(aq) + NaCl(aq)
   2.    
      1.    
         1. Dinitrogen tetraoxide// N₂O₄
         2. Oxygen
      2. 2Pb(NO₃)_2(s) → 2PbO(s) + 4 NO_2(g) + O_2(g)
      3. NO is odourless while N2O has a pleasant smell
         N₂O rekindles a glowing splint while NO does not
         NO gets oxidized to NO₂ while N₂O does not 
6.    
   1.    
      1. Enthalpy changes when converting reactants to products is the same regardless of the route by which the chemical change occurs
      2.      
         1.        
            
         2. ΔH1 = ΔH2 - ΔH3
            ΔH2 = (2x - 394) + (3x - 286) = -1646
            ΔH1 = -1646 + 1560 = 86kJmol
   2.      
      1. H = mcT
         = 500 x 4.2 x 19.5 
         = -40,950J // -40.95kJ
      2. Moles of C₂H5OH = ^1.5/₄₆ = 0.0326 moles
         H =  40.95 
                0.0326
         = 1256.13kJmol
      3. Heat lost to the surrounding
         Incorrect temperature readings
         Faulty apparatus
         Incomlete combustion
      4.      
         
      5. 1256.13 = 27.31kJ-1
              46
7.      
   1.      
      1. Anode
         Cathode
      2. Grey deposits of lead metal observed due to reduction of Pb2+ to Pb(s)
      3. 2Br(I) → Br_2(g) + 2e-
      4. Purification of metals
         extraction of highly reactive metals (Na & Al)
         electroplating
   2.      
      1.    
         1. mobile ions
         2. Delocalised electrons
      2. C. it does not conduct electricity in both solid and molten state and has high m.p & b.p