Organic Chemistry 1 Questions and Answers - Chemistry Form 3 Topical Revision

Questions

1. Use the flow chart below to answer the questions that follow:
   
   
   1. What observation would be made in process K?
   2. Name another conditions necessary for process J to take place
   3. Give the name of substance V
2. But-z-ene undergoes hydrogenation according to the equation given below
   CH₃CH = CHCH_{3 (g)} + H_2(g) → CH₃CH₂CH₂CH_3(g)
   1. Name the product formed when but-z-ene reacts with hydrogen gas
   2. State one industrial use of hydrogenation
3. Write the structures of the following compounds:-
   1. But-2-yne
   2. 2,2-dimethylpropane
4.  
   1. What is meant by Isomerism?
   2. Draw and name two Isomers of butane.
5. Study the information in the table below and answer the questions that follow:
   

   Ion	No. of protons	No. of electrons
   P3−	7	10
   Q+	19	18
   R2+	12	10

   
   
   1. Write the electron arrangement of element P.
   2. Give the group and period to which elements Q and R respectively.
      Q ……………………………………………………
      R ……………………………………………………
6. Compound W reacted with chlorine to form compound X only. The structural formula of X is shown below:
   
   
   1. Give the structural formula and name of compound W
   2. Name compound X ……………………………………………………………………
7. In petrol chemical industries, long chain alkanes are broken down in to simpler substances in a process called cracking
   1. Why is cracking necessary?
   2. State the two conditions required in cracking
   3. Draw the structure of 1-chloro-2, 2-dimethylpropane
8. In a reaction an alcohol K was converted to hex-1-ene
   Name reagent and condition necessary for the reaction above to occur
9.  
   1. Give the IUPAC systematic names of compounds Q and R
      Q: CH₂CHClCHClCH₂CH₃
      R: CH₃CHClCH₂ClCH3
   2. The organic compounds Q and R in (a) above, are formed when one mole of hydrocarbon b reacts with two moles of hydrogen chloride gas;
      1. Structural formula of N
      2. The IUPAC systematic name of N
10. Distinguish between the isotopes and isomers
11. Polymerisation of ethene takes place as shown in the equation below
    
    Name the type of polymerisation undergone by ethene in the reaction above
12. State Gay Lussac’s law
13. 10cm³ of methane (CH₄) gas is exploded with 150cm³ of air containing 20% oxygen and 80% nitrogen. The products were allowed to cool to room temperature. What will be the total volume of the gases at the end of the reaction?
14. Give the open structures of:-
    1. 3-chlorohex-1-yne
    2. CH₃OH
15. A fixed mass of gas occupies 105cm³ at -14^ºC and 650mmHg pressure. At what temperature in degrees Celsius will it have a volume of 15cm³ if the pressure is adjusted to 690mmHg pressure?
16. Write an equation for the reaction that takes place between ethene and concentrated Sulphuric (VI) acid
17. Petroleum (crude oil) is a mixture of several compounds which are separated in a Changamwe refinery by means of apparatus as shown below:
    
    
    1.  
       1. What is the name of the apparatus above
       2. What is the name of the process which is used in separation of crude oil
       3. What physical property of compounds in the mixture does the separation depend
       4. Use the letter A to G to describe where the following could be formed:.
          1. The fraction that represents gases
          2. The fraction that represents the largest molecules
          3. The fraction that represents liquids with the lowest boiling points
    2. State the use of product produce at
       G………………………………………………………………………………………
       C……………………………………………………………………………………….
    3. Draw apparatus for the separation of the product produce at D and water
18. Study the flow chart below and answer the questions that follow:
    
    
    1. Give the name of the substance CH ≡ CH …………………………………………
    2. To which group of hydrocarbons does the substance in (i) above belong?
    3. Give two reagents that can be used to prepare the substance named in (i) above
    4. State two physical properties of the substances in (i) above
    5. Give the names to the process in step I and 2
    6. Write an equation to show how substance A is formed
    7. Identify substance B ……………………………………………………
19. The diagram below represents a large-scale fractional distillation plant used to separate the components A, B, C and D in a mixture
    
    The components have the following average relative molecular masses not necessarily in that order; 282, 184, 44 and 128.
    1. What is the physical state of B at the position marked Q?
    2. Which component has an average relative molecular mass of 128? Explain
    3. State with a reason whether C is pure or impure
    4. Explain how the mixture is separated into its components
    5. Name two naturally occurring mixtures that are separated using this process
20.  
    1. The table below gives information about the major constituents of crude oil. Study it and answer the questions that follow:
       

       Constituent	Boiling point oC
       Gases	Below 40
       Petrol	40 -175
       Kerosene	175 - 250
       Diesel	250 - 350
       Lubricating oil	350 - 400
       Bitumen	Above 400

       
       
       1. Which of the constituents of crude has molecules with the highest number of carbon atoms? Explain
       2. Name the process you would use to separate a mixture of petrol and diesel and explain how the separation takes place
       3. Explain why the constituents of crude oil do not have a sharp boiling point
       4. Name the gas that is likely to be a constituent of crude oil and write its formula
    2.  
       1. What condition could cause a poisonous gas to be formed when kerosene is burnt. Explain
       2. Give one use of bitumen
21.  
    1. The set-up below was used to prepare ethyne gas
       
       
       1. Identify solid E
       2. Complete the diagram to show how the gas can be collected
       3. Write an equation to show how the gas is formed
       4. Complete the equation below: 
          C₂H₂ + 2I₂ →
       5. What is the role of sand in the experiment?
    2.  
       1. Explain the meaning of esterification
       2. Complete the equation below :
          CH₃COOCH₃ + H₂O →
       3. What type of reaction is occurring above
    3. Given the reaction:
                  _{solid F}
       C₈H₁₈    →     N + C₂H₄
       1. Identify substance:
          F………………………………… N………………………………
       2. Name the process represented above?
    4. Give one use of substance N
22.  
    1.  
       
       
       1. Name another source of hydrogen apart from electrolysis of water
       2. What conditions are necessary for step III to occur?
       3. Write the equation for the formation of colourless gas Q
       4. Give one use of nitric (V) acid
    2. State and explain the observations that would be made if a sample of copper metal is heated with concentrated nitric (V) acid
23.  
    1. Give the systematic names of the following compounds:-
       1. 
          
          ..........................................................................
       2. CH₃CH₂CH₂C ≡ CH .................................................................
    2. State the observations made when butan-1-ol reacts with:-
       1. Acidified potassium dichromate (VI) solution
       2. Potassium metal
    3. Ethanol obtained from glucose can be converted to ethene as shown below:-
                    _{Step I                Step II}
       C₆H₁₂O₆   →    C₂H₅OH    →   CH₂ = CH₂
       Name and describe the processes that take place in steps I and II
    4. Compounds A and B have the same molecular formula C₃H₆O₂. Compound A librates Carbon (IV) Oxide on addition of aqueous sodium carbonate while compound B does not. Compound B has a sweet smell. Draw the possible structures of:-
       1. Compound A
       2. Compound B
    5. Give two ways how the disposal of polymers such as polychloroethene by burning pollutes the environment
24.  
    1. Name the following compounds (CH₃)₃CCH₂CH₂CH₃
       Use the flow chart below to answer the questions that follow:-
       
    2.  
       1. Name the following :-
          1. Gas S ……………………………………………………………….…….
          2. Gas P …………………………………………………………………
          3. J ……………………………………………………………………….
       2. Name the processes involved in the following steps:
          1. Step I …………………………………………………………………………..
          2. Step II …………………………………………………………………………….
          3. Step III …………………………………………………………………………….
       3. Write a chemical equation for the complete combustion of substance M
       4. Name the condition and reagent in step III
          Condition ……………………………………………………………………………………
          Reagent …………………………………………………………………………………….
       5. Calculate the mass of salt R that would be formed by using 21.9 tonnes of N when it reacts with excess sodium hydroxide ( C= 12.0 H= 1.0 Na = 23)
       6.  
          1. Draw the structure of polymer K
          2. State one use of the above polymer
             ………………………………………………………………………………………………….
    3.  
       1. Name the class to which the following cleansing agents belong:-
          1. R – COONa⁺ ……………………………………………………
          2. 
             
             ……………………………………………………….
       2. Which cleaning agent above is not environmental friendly? Explain
25. The molecular formula of a hydrocarbon is C₆H₁₄. The hydrocarbon can be converted into two other hydrocarbon as shown by the equation below:
    C₆H₁₄ → C₂H₆ + X
    1. Name and draw the possible structural formula of X
    2. State and explain the observations that would be made if a few drops of bromine water were added to a sample of X
    3. Write an equation for the complete combustion of C₃H₈
26.  
    1. Give the names of the following
       1. CH₃CH₂CH₃
       2. CH₃CCCH₃
    2. Ethene is used in making polyethene bag in a process called polymerization
       1. Name the type of polymer that is formed when ethane polymerise
       2. Describe a simple chemical test that can be used to identify ethane gas in the laboratory
    3. Study the information in the table below and answer the questions that follow:-
       

       No. of carbon atoms	R.M.M of the Hydrocarbon
       2	28
       3	42
       4	56

       
       
       1. Write the general formula of the hydrocarbons in the table above
       2. Determine the molecular of a hydrocarbon with 5 carbon atoms and draw its structural formula
          Molecular formula
          Structural formula
    4. Study the scheme below and answer the questions that follow
       
       
       1.  Name the reagents in
          Step I ……………………………
          Step II ……………………………
          Step IV ………………
       2. Write an equation for the complete combustion of CH≡CH
       3. Give two uses of CH₄
27. Give the systematic names of the following compounds;
    1.  
       
    2. CH₃CH₂CH₂C≡ CH
28. Study the data given in the following table and answer the questions that follow. The letters are not the actual symbols of elements.
    

    Element	Number of protons	Melting Point	Bpt oC
    A	11	98	890
    B	12	650	1110
    C	13	60	2470
    D	14	1410	2360
    E	15	442  590	280
    F	16	113  119	445
    G	17	-101	-35
    H	18	-189	-386

    
    
    1. State and explain the trend in melting point in A B C
    2. Explain why the melting point and boiling points of element D is the highest
    3. Explain why the element represented by letter E has two melting point values
    4. Write down the chemical formula between element C and sulphate ions
    5. Name the chemical family in which H belong and state one use of the element
    6. What is the nature of the oxide of the elements represented by letters C and F?
29. Study the information in the table below and answer the questions that follow
    

    No. of carbon atoms	R.M.M of the Hydrocarbon
    2	28
    3	42
    4	56

    
    
    1. Write the general formula of the hydrocarbons in the table
    2. Predict the relative atomic mass of the hydrocarbons with 5 carbon atoms
    3. Determine the relative atomic mass of the hydrocarbon in (ii) above and draw its structural formula (H=1.0, C=12.0)
30. Substance “M” with a general formula C₂H_y burnt in chlorine gas with a red flame producing a cloud of black specks and colourless gas G.
    1. State the collective name for compounds which ‘M’ belongs
    2. With reason, state the identity of the black specks and colour gas “G”.
31.  
    1. 2.63g of a solution of sodium chloride at 20.0^oC was reacted with silver nitrate. After filtration, washing and drying, 2.36g of silver chloride was obtained. Determine the solubility of sodium chloride at 20.0^oC . (Na=23, Cl= 35.5, Ag = 108)
    2. Determine the number of moles of carbon (IV) Oxide gas produced when sodium carbonate reacted with dilute sulphuric (VI) acid (Molar gas volume =24dm³)
32. Write down all the isomers of but-z-ene and give their IUPAC names
33.  A hydrocarbon compound Z decolourizes bromine liquid in the presence of light but does not decolourize acidified potassium manganate (VII). Name and draw the structural formula of the eighth member of this homologous series
34.  
    1. What is meant by isomerism?
    2. Draw and name two isomers of Butyne

Answers

1.   
   1. Bromine decolorized immediately in ethane gas √1
   2. Temperature between150°C - 250°C or temperature of 180°C
   3. arbon (IV) oxide or CO2(g) √
2.  
   1. Butane
   2. Manufactures of cooking fats and margarine
3.  
    
4.   
   1. Existence of cpds with the same molecular formula but different structural formula/arrangement of atoms
   2.  
      
5.   
   1. 2.5
   2. Q Group 1 ✓½, Period 4 ✓½
      R Group 2 ✓½, Period 3 ✓½
6.   
   1.  
      
   2. 2,3 dichlorobutane
7. 1. To produce simpler hydrocarbons of industrial importance e.g. ethane which is widely used
   2. - Elevated temperature / high temperature 900 C
      - Catalyst
   3.  
      
      
8. Reagent: concentrated sulphuric acid
   Condition: temperature 180^o C
9.   
   1. H₂CHClCHClCH₂CH₃
      Name: 2, 3 dichloropentane
   2.   
      1. Structural Formula
         
         
      2. IUPAC name
         pent – 1,3 – diene
10. Isotopes are atoms of the same element with same atomic number but different mass numbers while isomers are compounds with the same molecular formula but different structural formula
11. Addition polymerization. √1
12.   
    1. When gases combine they do so in volume which bear a simple ratio to one another and to the product if gaseous under standard temperature and pressure
13. CH₄   +  2O_2(g) → CO_2(g) + 2H_2(l)
    10cm³   20cm³      10cm³✓½
    Volume of O₂ = ²⁰/₁₀₀ x 150
    = 30cm³
    Remaining volume of O₂ = 30 − 20=10 cm³
    Total volume of the gases = 20+10+10
    = 40cm³
14.  
    
    
15. T₂ = 690 × 15 × 259√
              650 × 105
    = 39.3K√
    = - 233.7° C√
16. CH₂ =CH_2(g) + H₂SO_4(l) → CH₃CH₂OSO₃H(aq) √ 1 mark
17.   
    1. 1. Fractional Column.
       2. fractional distillation.
       3. different boiling points.
       4. 1. A
          2. F
          3. B
    2. G – road making or water proofing
       C jet fuel or cooking and lighting.
    3.  
       
18.   
    1. ethyne
    2. Alkynes – because it has triple bond between the two carbon atoms
    3. Water and calcium carbide
    4. - Colourless, odourless
       - less denser than air
       - Insoluble in water but soluble in organic solvents
    5. Step 1 - Hydrogenation
       Step 2 - Halogenations
    6.  
       
    7. Carbon (IV) Oxide
19.   
    1. Gas /vapour
    2.  B - It has the second lowest boiling point thus second lowest molecular mass
    3. C is impure since it boils over a range of temperature
    4. It is boiled heated and the vapour of the components condense at different temperatures
    5. - Liquid air
       - Crude oil
20.   
    1.   
       1. Bitumen it has the highest boiling point
       2.  Fractional distillation; during distillation petrol would distill off at 175^oC, while diesel will distill at 35⁰C
       3. Each component is a mixture of hydrocarbons which have different boiling points
       4. Methane, CH₄, EthaneC₂H₆ propane, C₃H₈, Butane C₄H₁₀
    2.   
       1. Burning in limited amount of air will produce carbon monoxide (carbon (II) Oxide) which is poisonous
       2. Manufacture of Tar used in road tarmacking sealing of leakages on roofs
21.   
    1.   
       1. Calcium carbide – CaC₂
       2. Over water method
          
          
       3. CaC_2(s) + 2H₂O_(s) + 2H₂O_(l) → Ca(OH)_2(aq) + C₂H_2(g)
       4. C₂H₂ + 2I₂ → C₂H₂I₂
       5. The reaction if highly exothermic hence sand helps to absorb excess heat.
    2.   
       1. A reaction in which an organism acid reacts with an alkanol to form a sweet smelling compound called ester.
       2. CH₃COOCH₃ + H₂O → CH₃COOH + CH₃OH
       3. Hydrolysis
    3.   
       1. F – Aluminium oxide – Al₂O₃
          N – C₆H₁₄ – Hexane
       2. Cracking
          
    4. A fuel
22.   
    1.   
       1. Cracking of crude oil fractions. √1
       2. Temp – 400 – 500⁰c
          Pressure – 200 – 500 atmospheric Any 2 = 1
          Catalyst – Finally divided iron.
       3. 4NH_3(g) + 5O_2(g) → 4NO_(g) + 6H₂O_(l)
          
       4. - Manufacture of nitrate fertilizers. √1
          - Manufacture of explosives.
          - Purification of metals.
    2. - Red brown gas √1 with pungent irritating smell due to reduction of HNO₃ to NO₂
       - Blue √1 solution due to formation of Cu (NO₃)₂
23.   
    1.   
       1. 2-bromo propene or 2- bromo prop-i-ene
       2. Pent-i-ene
    2.   
       1. Changes form orange to Green
       2. Effervescence//bubbles of gas produced
    3. Step 1
       - Fermentation of glucose
       Glucose broken down in obscene of oxygen using enzymes
       - Dehydration of ethanol; using concentrated sulphuric (VI) acid and high temperature of 170^oC
       
       Step II
       - Dehydration of ethanol; using concentrated sulphuric (VI) acid and high temperature of 170^oC
    4. Compound A
    5. - release chlorine gas which destroy ozone layer
       - Chlorine gas combines with vapour in atmosphere to form acid rain which destroy vegetation
       - Chlorine gas can cause respiratory diseases
24.   
    1. 2,2 – dimethyl pentane
    2.   
       1.   
          1. carbon IV oxide.
          2. Hydrogen gas.
          3. Propane.
       2.   
          1. Hydrogenation.
          2. Neutralization
          3. substitution
       3. CH₃CH₂CH₂O_(l) + 90_{2 (g)} → 6 CO_{2 (g)} + 8 H₂O_(l)
       4. Condition Presence of U.V light
          Reagents – Chlorine gas
       5. CH₃CH₂COOH + NaOH → CH₃CH₂COONa + H₂O_(l)
          Mole ratio :
          74 tones of acid  =  96 tones of salt
          21.9                  = ?            
          21.9 × 96 = 28.4 tones
                74
          Or 21.9 = 0.29 moles of salt
                74
          = 0.29 × 96 = 28.4 tones
       6.   
          1.  
             
          2. use in making – Plastic crates plastic boxes plastic ropes
             
             
    3.   
       1.   
          1. soapy detergent
          2. Soap less detergent
       2. Soap less Detergent - non biodegradable.
25.   
    1.  
       
       
    2. Bromine water is decolourised because X is unsaturated or has a (-C = C-) double bond.
    3. C₃H_8(g) + 5O_2(g) → 3CO_2(g) + 4H₂O_(l)
26.   
    1.   
       1. Propane
       2. But - 2 - yne
    2.   
       1. Ploythene
       2. Bubble pass ethane gas in acidified KMnO4 or acidified K₂Cr₂O₇
          
    3.   
       1. C_nH_2n
       2. C₅H₁₀
    4.   
       1. Step I – hydrogen
          Step II – Hydrogen chloride
          Step IV – Sodalime
       2. 2CH = CH_(g) + O_2(g) → 4CO_2(g) + 2H₂O_(l)
          - A fuel
          - Manufacture of methanol
          - Manufacture of methanol
27.   
    1. 2 – Methylprop – 1 - ene 
    2. Pent – 4 – yne
       ✓ 1 mark
       ✓ 1 mark [Total 12 marks]
28.   
    1. The melting point increases from A to C this is due to increase in number delocalized electron hence increase in the strength of metallic bond.
    2. forms a giant structure with strong covalent bonds. Hence high melting.
    3. It exhibits allotopy ie may exist as two different form in the same state.
    4. C₂(SO₄)₃
    5. Noble gases or inert
       - Used in filament bubls
       - Used to produce an inert atmosphere in high temperature inetallurgical processes e.g welding.
    6. C is amphoteric oxide
       - F acidic it is non –metal oxide.
29.    
    1. CnH2n, where n = No. of carbon atoms
    2. 70
    3. C₅H₁₀, CH₃CH=CHCH₂CH₃
       OR CH₃CH₂CHCH₂= CH₂
30.   
    1. Hydrocarbon. √1
    2. Black specks is carbon
       Colourless gas is steam √1 3
       Hydrocarbon burn in air to form carbon √ ½ and water√½
31.   
    1. NaCl_(aq) + AgNO_3(aq) → NaNO_3(aq) + AgCl_(s)
       Moles of AgCl= Mass
                             R.F.M
       = ^2.36/_143.5
       = 0.016446moles
       Mole ratio NaCl : AgCl
                          1  : 1
       Moles of NaCl = 0.61446moles
       Mass of NaCl = RFM x moles
       = 58.5 x 0.016446
       = 0.962091g
       Mass of solvent (water) = 2.63 – 0.962091
       = 1.667909g
       1.667909g of water dissolves 0.962091g of NaCl
       100g of water dissolves = 100 x 0.962091g
                                               1.667909
       = ^57.68/_100g of water
    2. 24000cm³ = 1mol
       80cm³ = 80x1
                    2400
       = 0.00333moles
32.   
    
    1. CH₃CH = CHCH₃ – But-2-ene
    2. 2– methyl 1 prop-2-ene
    3. CH₂ = CHCH₂CH₃ – But-1-ene
33. Octane
    or CH₃CH₂CH₂CH₂CH₂CH₂CH₂CH₃
34.   
    1. Existence of same molecular formula but different structural formula √1
    2.