Chemistry Paper 2 Questions - Kapsabet Boys Post Mock 2023 Exams

 INSTRUCTIONS

•  Answer all the questions
• Mathematical tables and silent electronic calculators may be used.
• All working must be clearly shown where necessary.
• All answers should be written in English.

QUESTIONS

1. The grid below represents part of a periodic table study and answers the questions that follow. The letters do not represent the actual symbols of the elements.
   
   
   1. What name is given to the family of the;
      1. Elements to which E, H and M belong? (1mk)
      2. Elements to which F, J and K belong? (1mk)
   2. Write the chemical formula of the;
      1. Sulphate of T. (1mk)
      2. Nitrate of J. (1mk)
   3. Name the type of bond and structure formed between in a compound of; (1mk)
      1. D and N.
         Bond……………………………………………………………………………..
         Structure………………………………………………………………………..
      2. T and H. (1mk)
         Bond: …………………………………………………………….
         Structure: ……………………………………………………………
   4.  
      1. Ionic radius of element E is bigger than its atomic radius. Explain. (2mks)
      2. The oxide of G has a lower melting point than the oxide of L. Explain. (2mks)
      3. Explain in terms of structure and bonding the following observations. There is an increase in melting and boiling point from W to T. (2mks)
   5. Using dots (•) and crosses diagram show bonding in ZV₄⁺. (1mk)
2.  
   1. The table below shows information about chlorides of some period 3 elements
      

      Chloride	NaCl	MgCl2	AlCl3		SiCl4	PCl5
      Melting Point (0C)	801	712	Sublimes 183	at	-70	-90

      
      
      1. State the nature of the solution formed when the following chlorides are
         dissolved in water. Explain (2mks)
         NaC
         AlCl₃
      2. Explain why AlCl₃ has much lower melting point than Mg Cl₂ although both Al and Mg are metals
         (2mks)
      3. Draw (.) and cross(x) diagram to show bonding in:
         MgCl₂ (1mk)
         SiCl₄ (1mk)
      4. Identify the type of bonding in each case (1mk)
   2. 10cm³ of water was placed in a test tube and the initial temperature of the water recorded. A spatula of Si Cl₄ was added to the water and the final temperature recorded when the entire solid had dissolved.
      1. Explain the observations made. (2mks)
      2. Write an equation for the reaction that occurred (1mk)
3.  
   1. The diagram below shows a setup which was used to investigate the effect of electricity on solid and molten lead(II) iodide. Study it and answer the questions that follow.
      
      
      1. The bulb only lit after the Lead (II) iodide had melted .Explain (1mk)
      2. State and explain the observation at the anode when the circuit is completed. (1mk)
      3. What precaution should be taken when carrying out this experiment (1mk)
      4. Write the equation for the reaction taking place as the cathode (1mk)
      5. On the diagram; indicate the movement of ions in the electrolyte. (1mk)
      6. When a current was passed through 23.6g of molten Lead (II) iodide for 3 mins 5 secs 19.1g of the electrolyte remained. Calculate the amount of current passed. (3mks)
   2. Given the following standard electrode potentials;
      Cu ²⁺ _(ag)→ + 2e- Cu _^(s) E0 = + 0.34V
      Zn 2+ _(ag) →+ 2 e- Zn_(s) E0 = - 0.77V
      Explain whether it's advisable to store a solution of Zinc sulphate in a copper can. (2mks)
4. The flow chart below represents preparation of oxygen gas. Study it and answer the questions that follow.
   
   
   1. Identify the following substances. (2mks)
      1. Solid A………………………………………………………………………..
      2. Gas D………………………………………………………………………….
      3. Solid Q………………………………………………………………………….
      4. Solution M……………………………………………………………………….
   2. Write a chemical equation for the:
      1. Formation of solid G. (1mk)
      2. Gas D. (1mk)
      3. Blue solution (1mk)
      4. In Step I. (1mk)
   3. State the confirmatory that for oxygen gas. (1mk)
   4. Write the ionic equation for the reaction taking place in process P. (1mk)
   5. State one use of oxygen. (1mk)
5.  
   1. The set up below represents the arrangement used to prepare substance S by passing a stream of dry hydrogen chloride gas over heated iron wool.
      
      
      1. Correct the mistake in the set up above. (1mk)
      2. Give the chemical equations for the reaction that involves
         1. Formation of substance S. (1mk)
         2. The reaction at point x. (1mk)
         3. What precaution would you take when carrying out this experiment? Give reasons. (2mks)
   2. 300cm³ of hydrogen chloride gas were passed over 7.0g of heated iron wool until there was no further change. The reaction vessel was then allowed to cool to room temperature.
      1. Determine the mass of iron that remained at the end of the experiment.
         (Molar gas volume = 24000cm³, Fe=56). (2mks)
      2. Determine the volume of 2M sulphuric acid that would be required to react with excess iron that remained in the above experiment b(i) above. (2mks)
   3. What would you observe when sodium hydroxide solution is added to the aqueous solution of the product formed in (a) above. Explain. (2mks)
6.  
   1. Solubility of salt X and Y were determined at different temperatures as shown in the following data.
      

      Temperature (ºC)		0	20	40	60	80	100
      Solubility of 100g of water	X	12	30	75	125	185	250
      	Y	15	20	35	45	65	80

      
      
      
      1. On the grid provided, plot a graph of solubility (vertical axis) against temperature. (4mks)
      2. From the graph determine the solubility of each at 50ºC.
         X ……………………………………………………….. (1mk)
         Y ………………………………………………………… (1mk)
      3. At what temperature was the solubility of both salts equal. (1mk)
      4. Saturated solution of salt X at 70ºC was cooled to 20ºC. What mass of the crystal were deposited. (1mk)
   2.  
      1. What is permanent hardness of water? (1mk)
      2. State two chemical substance that can be used to remove permanent hardness in water. (1mk)
   3. Explain why aluminium sulphate solution is acidic. (1mk)
7.  
   1. Use the bond energies given below to calculate the enthalpy change for the reaction. (2mks)
      C₂H_6(g) + Br_2(g)  C₂H₅Br(g) + HBr(g)
      

      Bond	C–H	C–Br	Br–Br	H–Br	C–C
      Bond energy (kJ)	413	280	193	365	343

   2. Hydrogen peroxide decomposes according to the equation below.
      H₂O_(l)  H₂O_(l) + ½O_g H = –98kJ/mol
      If 6.8g of hydrogen peroxide contained 75cm3 of solution in water were decomposed, determine the rise in temperature due to the reaction. (Specific heat capacity of water =
      4.2g-k-,density of water = 1g/cm³. (O =16, H =1) (2mks)
   3. On the space provided below sketch the cooling curve that would be obtained when a boiling tube containing water at 80ºC is immersed in a freezing mixture maintained at – 10º (3mks)
   4. Butane C₄H₁₀ cannot be prepared directly from its elements but its standard heat of formation DHf^ can be obtained directly. The following are some heats of combustion.
      H_C^ Carbon (S) = – 393kJ/mol
      H_C^ (H₂)_(g) = –286 kJ/mol
      H_C^ (C₄H₁₀) = –2877kJ/mol
      1. Draw an energy cycle diagram linking the heat of formation of butane with its heat of combustion and heat of combustion of its constituent elements. (2mks)
      2. Calculate the heat of formation of butane Hf^(C₄H₁₀) (2mks)
   5. Given that the lattice energy of potassium chloride is +690Kj/mol and hydration enthalpies of K⁺ and Cl- are –322kJ/mol and – 364kJ/mol respectively. Calculate the enthalpy of solution of potassium chloride. (2mks)