Form 4 Chemistry imtixaanka qaranka 2020 iyo jawaabihiisa

PART A (10 MARKS)

Choose the correct answer and write it in the answer booklet (10 Marks)

1. A1

   Which of the following organic compounds is unsaturated?

   • A.Ethylcyclobutane
   • B.3-ethyl-2-methyl-1-pentene
   • C.2-bromobutane
   • D.2-methyl-1-chlorohexane

   1 dhibcood
2. A2

   Alkanes have a general formula of:

   • A.CnH2n-1
   • B.CnH2n+1
   • C.CnH2n+2
   • D.CnH2n

   1 dhibcood
3. A3

   The oxidation number of Chromium (Cr) in potassium dichromate (K2Cr2O7) is:

   • A.+2
   • B.+6
   • C.+3
   • D.+5

   1 dhibcood
4. A4

   The Chemical reaction in which heat is released is:

   • A.Exothermic
   • B.Endothermic
   • C.Isomeric
   • D.Precipitation

   1 dhibcood
5. A5

   To which family of Organic Compound does CH3COCH2CH3 belong to:

   • A.Alcohol
   • B.Aldehyde
   • C.Ketone
   • D.Carboxylic Acid

   1 dhibcood
6. A6

   The general formula of aldehydes is:

   • A.R-CHO
   • B.R-OH
   • C.R-COOH
   • D.R-COOR

   1 dhibcood
7. A7

   Which of the following is an allotrope of Carbon:

   • A.Diamond
   • B.Sulphur
   • C.Nitrogen
   • D.aluminium

   1 dhibcood
8. A8

   Identify the Structure of methylbutanoate in the choices below:

   • A.CH3COOC2H5
   • B.C3H7COOCH3
   • C.HCOOC3H7
   • D.CH3OC4H9

   1 dhibcood
9. A9

   Which of the following is the first synthetic organic molecule?

   • A.NH4CNO
   • B.C4H10
   • C.NH4Cl
   • D.(NH2)2CO

   1 dhibcood
10. A10

    What do we call the compounds with the same molecular formula but different structures?

    • A.Isotopes
    • B.Allotropes
    • C.Isomers
    • D.Homologous series

    1 dhibcood

PART B: (10 MARKS)

Choose the correct answer for each of the blanks below and write it in the answer booklet

1. B1

   The general formula of alkenes is _____

   2 dhibcood
2. B2

   Organics acids are also known as _____

   2 dhibcood
3. B3

   The functional group of alcohol is called _____

   2 dhibcood
4. B4

   The combustion reaction of organic compounds produces water _____ and energy.

   2 dhibcood
5. B5

   The organic compounds that contain only carbon and hydrogen atoms are called _____

   2 dhibcood

PART C: (80 MARKS)

Answer the following Questions in the answer booklet.

1. 1a

   Define the term "Allotropes"

   1 dhibcood
2. 1b

   State the three Allotropes of Carbon?

   3 dhibcood
3. 2

   Write down the balanced chemical equation for the hydrogenation of ethene to ethane

   3 dhibcood
4. 3a

   Differentiate between the following pairs: Secondary alcohol and tertiary alcohol

   2 dhibcood
5. 3b

   Differentiate between the following pairs: Carbonyl group and carboxyl group

   2 dhibcood
6. 3c

   Differentiate between the following pairs: An aldehyde and ketone

   2 dhibcood
7. 4

   What was the first organic compound to be prepared in the laboratory?

   2 dhibcood
8. 5

   At a given temperature, the reaction CO(g) + H2O(g) <=> H2(g) + CO2(g) produces the following concentrations at an equilibrium of: [CO] = 0.200 M; [H2O] = 0.500 M; [H2] = 0.320 M; [CO2] = 0.420 M. Find K.

   5 dhibcood
9. 6

   What do we mean by the term aromatic compounds?

   1 dhibcood
10. 7

    Write down the molecular formula for the following hydrocarbons: pentane, pentene, pentyne, 1, 2-dibromobenzene

    4 dhibcood
11. 8

    Explain why are enzymes referred to as catalysts?

    2 dhibcood
12. 9

    Name the following organic compounds: (i) CH3-CH2-CH3; (ii) CH3-CH2-CH2-CH=CH2; (iii) CH3-CH2-CH(CH3)-CH2-CH(CH2-CH3)-CH2-CH2-CH3; (iv) H3C-CH=CH-CH(CH3)-CH2-CH2-CH3

    4 dhibcood
13. 10

    Explain why the oxidation number of group one elements in the periodic table is always one.

    2 dhibcood
14. 11

    Give the name of the following structure: CH3-C≡C-CH(CH3)-CH2-CH3

    2 dhibcood
15. 12

    Draw the structural formula for the following hydrocarbons: Ethene, 2-Butyne, 4-methyl-2-hexyne, 5-ethyl-3-octyne

    4 dhibcood
16. 13

    State the chemical equation for hydrogenation of propene to form propane

    2 dhibcood
17. 14

    Classify the following molecules into saturated and Unsaturated: Pentene, Hexane, Butene, Heptyne

    4 dhibcood
18. 15

    In the equation below, show the oxidizing and reducing agents: 4Al(s) + 3O2(g) -> 2Al2O3(s)

    2 dhibcood
19. 16

    Distinguish between endothermic and exothermic reactions.

    2 dhibcood
20. 17

    Categorize the following into endothermic and exothermic reactions: Melting of ice cream, Burning of a paper, Oxidation of carbohydrates in the body, Combustion of fuel

    4 dhibcood
21. 18

    Balance the following chemical equation: N2(g) + H2 -> NH3(g)

    1 dhibcood
22. 19

    Using Boyles law describe the relationship between volume and pressure.

    3 dhibcood
23. 20

    Draw the condensation reaction of two glucose molecules to produce a maltose.

    2 dhibcood
24. 21

    Define the term "molecular weight".

    1 dhibcood
25. 22

    Explain why Aldehydes and ketones are called carbonyl compounds?

    2 dhibcood
26. 23

    Why is the oxidation state of an atom in the halogen family -1?

    2 dhibcood
27. 24

    Calculate the reaction rate of A(g) + B(g) +C(g) + D(g), given the initial concentrations [A] = 0.10 M and [B] = 0.20 M, and given the reaction constant, k = 0.015 L/mol·s.

    4 dhibcood
28. 25

    Describe the process required to convert liquid into gas?

    2 dhibcood
29. 26

    Define the following terms: Oxidizing agent, Hybridization, Isomer

    3 dhibcood
30. 27

    State the chemical reactions that alkanes undergo.

    4 dhibcood
31. 28

    Write the common element that compose hydrocarbons.

    3 dhibcood

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