Organic Chemistry 2 Questions and Answers - Chemistry Form 4 Topical Revision

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Questions

A student mixed equal volumes of Ethanol and butanoic acid. He added a few drops of concentrated Sulphuric (VI) acid and warmed the mixture
1. Name and write the formula of the main products
  Name………………………………….
  Formula……………………………………..
2. Which homologous series does the product named in (i) above belong?
The structure of the monomer phenyl ethene is given below:-
1. Give the structure of the polymer formed when four of the monomers are added together
2. Give the name of the polymer formed in (a) above
Explain the environmental effects of burning plastics in air as a disposal method
Write chemical equation to represent the effect of heat on ammonium carbonate
Sodium octadecanoate has a chemical formula CH₃(CH₂)₆COO^-Na⁺, which is used as soap.
Explain why a lot of soap is needed when washing with hard water
A natural polymer is made up of the monomer:
1. Write the structural formula of the repeat unit of the polymer
2. When 5.0 x 10-5 moles of the polymer were hydrolysed, 0.515g of the monomer were obtained.
  Determine the number of the monomer molecules in this polymer.
  (C = 12; H = 1; N = 14; O =16)
The formula below represents active ingredients of two cleansing agents A and B

Which one of the cleansing agents would be suitable to be used in water containing magnesium hydrogen carbonate? Explain
Study the polymer below and use it to answer the questions that follow:
1. Give the name of the monomer and draw its structures
2. Identify the type of polymerization that takes place
3. State one advantage of synthetic polymers
Ethanol and Pentane are miscible liquids. Explain how water can be used to separate a mixture of ethanol and pentane
1. What is absolute ethanol?
2. State two conditions required for process G to take place efficiently
1. The table below shows the volume of oxygen obtained per unit time when hydrogen peroxide was decomposed in the presence of manganese (IV) Oxide. Use it to answer the questions that follow:-
  
  Time in seconds Volume of Oxygen evolved
  (cm³)
  
  0
  30
  60
  90
  120
  150
  180
  210
  240
  270
  300 0
  10
  19
  27
  34
  38
  43
  45
  45
  45
  45
  1. Plot a graph of volume of oxygen gas against time
  2. Determine the rate of reaction at time 156 seconds
  3. From the graph, find the time taken for 18cm³ of oxygen to be produced
  4. Write a chemical equation to show how hydrogen peroxide decomposes in the presence of manganese (IV) Oxide
2. The diagram below shows how a Le’clanche (Dry cell) appears:-
  1. What is the function of MnO₂ in the cell above?
  2. Write the equation of a reaction that occurs at the cathode
  3. Calculate the mass of Zinc that is consumed when a current of 0.1 amperes flows through the above cell for 30minutes (1F =96500c Zn =65)
1. Give the IUPAC names of the following compounds:
  1. CH₃COOCH₂CH₃
2. The structure below shows some reactions starting with ethanol. Study it and answer the questions that follow:
  1. Write the formula of the organic compounds P and S
  2. Name the type of reaction, the reagent(s) and condition for the reactions in the following steps :-
    1. Step I
    2. Step II
    3. Step III
  3. Name reagent R ……………………………………………………………
  4. Draw the structural formula of T and give its name
  5. 1. Name compound U………………………………………………………..
    2. If the relative molecular mass of U is 42000, determine the value of n (C=12, H=1)
3. State why C₂H₄ burns with a more smoky flame than C₂H₆
1. State two factors that affect the properties of a polymer
2. Name the compound with the formula below :
  CH₃CH₂CH₂ONa
3. Study the scheme below and use it to answer the questions that follow:-
  1. Name the following compounds:-
    1. Product T …………………………
    2. K ………
  2. State one common physical property of substance G
  3. State the type of reaction that occurred in step J
  4. Give one use of substance K
  5. Write an equation for the combustion of compound P
  6. Explain how compounds CH₃CH₂COOH and CH₃CH₂CH₂OH can be distinguished chemically
  7. If a polymer K has relative molecular mass of 12,600, calculate the value of n (H=1 C =12)
Study the scheme given below and answer the questions that follow:-
1. 1. Name compound P ……………………………………………………………………
  2. Write an equation for the reaction between CH₃CH₂COOH and Na₂CO₃
2. State one use of polymer Q
3. Name one oxidising agent that can be used in step II …………………………………..
4. A sample of polymer Q is found to have a molecular mass of 4200. Determine the number of monomers in the polymer (H = 1, C = 12)
5. Name the type of reaction in step I …………………………………………………………..
6. State one industrial application of step III
7. State how burning can be used to distinguish between propane and propyne. Explain your answer
8. 1000cm3 of ethene (C₂H₄) burnt in oxygen to produce Carbon (II) Oxide and water vapour.
  Calculate the minimum volume of air needed for the complete combustion of ethene
  (Air contains 20% by volume of oxygen)
Study the schematic diagram below and answer the questions that follow:-
1. Identify the following:
  Substance Q ..............................................................................................................
  Substance R...............................................................................................................
  Gas P..........................................................................................................................
2. Name:
  Step 1.................................................................................................
  Step 4.................................................................................................
3. Draw the structural formula of the major product of step 5
4. State the condition and reagent in step 3
Study the flow chart below and answer the questions that follow
1. Name the following organic compounds:
  M……………………………………………………………..……..
  L…………………………………………………………………..
2. Name the process in step:
  Step 2 ………………………………………………………….….
  Step 4 ………………………………………………………….…
3. Identify the reagent P and Q
4. Write an equation for the reaction between CH₃CH₂CH₂OH and sodium
Give the names of the following compounds:
1. CH₃CH₂CH₂CH₂OH ……………………………………………………………………
2. CH₃CH₂COOH …………………………………………………………………
3. CH₃C – O – CH₂CH₃ ……………………………………………………………………
Study the scheme given below and answer the questions that follow;
1. Name the reagents used in:
  Step I: ………………………………………………………………………
  Step II ……………………………………………………………………
  Step III ………………………………………………………………………
2. Write an equation to show products formed for the complete combustion of CH = CH
3. Explain one disadvantage of continued use of items made form the compound formed in step III
A hydrated salt has the following composition by mass. Iron 20.2%, oxygen 23.0%, sulphur 11.5%, water 45.3%
1. Determine the formula of the hydrated salt (Fe=56, S=32, O=16, H=11)
2. 6.95g of the hydrated salt in c(i) above were dissolved in distilled water and the total volume made to 250cm³ of solution. Calculate the concentration of the resulting salt solution in moles per litre. (Given that the molecula mass of the salt is 278)
Give the IUPAC name for each of the following organic compounds;
3. CH₃COOCH₂CH₂CH₃
The structure below represents a cleansing agent.
1. State the type of cleansing agent represented above
2. State one advantage and one disadvantage of using the above cleansing agent.
The structure below shows part of polymer .Use it to answer the questions that follow.
1. Derive the structure of the monomer
2. Name the type of polymerization represented above
The flow chart below represents a series of reactions starting with ethanoic acid:-
1. Identify substances A and B
2. Name the process I
1. Write an equation showing how ammonium nitrate may be prepared starting with ammonia gas
2. Calculate the maximum mass of ammonium nitrate that can be prepared using 5.3kg of ammonia (H=1, N=14, O=16)
1. What is meant by the term, esterification?
2. Draw the structural formulae of two compounds that may be reacted to form ethylpropanoate
1. Draw the structure of pentanoic acid
2. Draw the structure and give the name of the organic compound formed when ethanol reacts with pentanoic acid in presence of concentrated sulphuric acid
The scheme below shows some reactions starting with ethanol. Study it and answer the questions that follow:-
1. Name and draw the structure of substance Q
2. Give the names of the reactions that take place in steps 2 and 4
3. What reagent is necessary for reaction that takes place in step 3
Substances A and B are represented by the formulae ROH and RCOOH respectively.
They belong to two different homologous series of organic compounds. If both A and B react with potassium metal:
1. Name the common product produced by both
2. State the observation made when each of the samples A and B are reacted with sodium hydrogen carbonate
  1. A
  2. B
Below are structures of particles. Use it to answer questions that follow. In each case only electrons in the outermost energy level are shown

Identify the particle which is an anion
Plastics and rubber are extensively used to cover electrical wires.
1. What term is used to describe plastic and rubbers used in this way?
2. Explain why plastics and rubbers are used this way
The scheme below represents the manufacture of a cleaning agent X
1. Draw the structure of X and state the type of cleaning agent to which X belong
2. State one disadvantage of using X as a cleaning agent
Y grams of a radioactive isotope take 120 days to decay to 3.5grams. The half-life period of the isotope is 20 days
1. Find the initial mass of the isotope
2. Give one application of radioactivity in agriculture
The structure below represents a polymer. Study and answer the questions that follow:-
1. Name the polymer above..................................................................................
2. Determine the value of n if giant molecule had relative molecular mass of 4956
RCOO-Na+ and RCH₂OSO₃^-Na⁺ are two types of cleansing agents;
1. Name the class of cleansing agents to which each belongs
2. Which one of these agents in (i) above would be more suitable when washing with water from the Indian ocean. Explain
3. Both sulphur (IV) oxide and chlorine are used bleaching agents. Explain the difference in their bleaching properties
The formula given below represents a portion of a polymer
1. Give the name of the polymer
2. Draw the structure of the monomer used to manufacture the polymer

Answers

1. Ethylbutanoate
2. CH₃CH₂CH₂
3. Esters
2. Polypheny/ ethane
Plastics may contain chlorine or fluorine compounds apart from hydrogen and carbon when burnt, fluorine and chlorine compounds are released into the air destroying Ozone layer
(NH₄)₂CO_3(s)→ 2NH_3(g) + CO_2(g) + H₂O_(l)
The first amount of soap precipitates Ca²⁺_(aq) and Mg²⁺_(aq) ions and soften water.
Then additional soap dissolves oil from the fabric.
2. .00005mol. P = 0.515 g of monomer.
  = 1.0 mole of poly mer = 1 × 0.515 = 10300 g
  0.0005
  RFM ( C₄H₉NO₂)n = 48 + 9 + 32 = 103
  = (C₄H₉NO₂) = 10300
  103n = 10300
  ∴ n = 100 molecules
Agent A – magnesium salt formed is soluble hence doesn’t form scum
1. Styrene/Phenylethene
2. Addition polymerization
3. – can be made into different shapes easily
  - are cheaper
  - are not corroded by acids, alkalis or air
  - are stronger and long lasting
  - are water-proof
  (any 1 correct)
– Add water to the mixture and shake where ethanol dissolves in water while pentane is immiscible.
- Transfer the mixture in a separating funnel and allow it to settle when pentane floats on top of water-ethanol mixture.
- Turn on the tap to collect water-ethanol mixture while pentane remains in the separating funnel.
- Separate ethanol from water by fractional distillation based on the differences in boiling points.
1. Is 100% ethanol/is pure ethanol without water in it
2. 30^oC and yeast
1. 2. R = Δv
    Δ t
    = 43 – 40.5
    180 -150
    = 25
    30
    = 0.0833cm³/s
  3. 57seconds
  4. 2H₂O_2(l) → 2H₂O_(l) + O_2(g)
2. 1. To oxidize H2 produced to water
  2. Z
  3. Q = 1t
    = 0.1 x 30 x 60
    = 180C
    96500c = 1F
    180c = ?
    180 x 1
    96500
    = 0.001865F
    Zn_(s) → Zn²⁺_(aq) + 2e^-2F = 65g
    0.001865F = 0.001865 x 65
    2
    = 0.0606g of Zn was consumed
1. 1. Ethylethanoate.
  2. 2 – bromobut – 1 – ene
2. 1. P – CH₃COOCH₂ CH3
    S – CH₃CHONa
  2. 1. Step I -Type – dehydration.
      Reagent – Concentrated sulphur acid.
    2. Step II- Type – Oxidation
      Reagent – acidified potassium magnate VII/ Potassium dichromate (VI)
    3. Step III- Type – Hydrogenation
      Reagent – Hydrogen
  3. R – Soda lime
  5. 1. U – Polythene/Polyethene
    2. 28n = 42000
      n = 42000 = 1500
      28
3. – It is unsaturated.
1. - The length of the chain
  - Intermolecular forces
  - Cross linking of the molecules (Any two correct = 2 marks)
2. Sodium propoxide
3. 1. 1. – T is ethane
    2. – K is polypropene
  2. has a sweet smell
  3. Neutralization
  4. - Used to make ropes √ 1 mark
    - Used to make crates of bottles
    - Used as surface for all weather football and hockey pitches (Any correct use)
  5. CH₃CH₂CH₃ + SO₂ → 3CO₂ + 4H₂O
    (N.B ignore state symbols)
  6. React a small sample of each of the two substances with sodium carbonate separately. Bubbles// efferrescence are observed with CH₃CH₂COOH and no reaction with CH₃CH₂CH₂OH
  7. RMM of monomer = 42 √ ½
    42n = 12600
    N = 12600 = 300√ ½
    42
1. 1. Propene √1
  2. 2CH₃CH₂COOH + Na₂CO₃√½ → 2CH₃CH₂COONa + CO₂ + H₂O
2. Making packing materials √1
3. KMnO₄√½ /K₂CrO₇
4. 42n√ = 4200
  n = ⁴²⁰⁰∕₄₂= 100 √
5. Esterification √1
6. Conversion of oils to fats. √1
7. Propane burns with a clear falme√1 while propyne burns with a sooty flame √1because propyne has a higher √1 C : H ration than propane.
8. C₂H_4(g) + 3O_2(g) → 2CO_2(g) + 2H₂O_(l) √1
  1 Vol. 3 vol
  1 Vol. = 1000 cm³ √½
  Vol of O₂ required = 3 x 1000 cm³ = 3000 cm³ √½
  Vol of air required = 100 x 3000 cm³ 20
  = 15,000 cm3√½
1. 1. Q - CH3CH2COOH (accept name (propanoic acid)
    R – CH3CH2COOH (Propanoic acid)
    P- Hydrogen
  2. Step I Esterification
    Step 4 – Oxidation
  4. Condition – 180 – 250^oC
    reagent – Conc. H₂SO₄
1. M: Ethan – 1, 2- diol
  L: Ethanoic acid
2. Step 2: Polymerisation
  Step 4: Hydrogenation
3. Concentrated sulphuric acid
  Ethanoic acid
1. Butan – 1 – ol// 1- Butanol// n-Butanol
2. Propanoic acid
3. Ethylethanoate
1. Step I: Hydrogen
  Step II: Hydrogen chloride gas// HCl
  Step III: Sodium hydroxide/ NaOH/ Sodalime
2. 2C₂H_2(g) + 5O_2(g) → 4CO_2(g) + 2H₂O_(g)
3. Environmental pollutant
  It is not biodegradable/ Not decomposed by bacterial
1. Fe S O H₂O
  ^20.2/₅₆ ^11.5/₃₂ ^23.0/₁₆ ^45.3/₁₈
  ^0.36/_0.36 0.36/0.36 1.44/0.36 2.52/0.36
  1 1 4 7
  Empirical formula: FeSO₄.7H₂O
2. 6.95g = 6.95/278 = 0.025
  ∴ 0.05 moles in 250cm3 = 0.025 x 1000/250 = 0.1
  Concentration = 6.95/278 x 1000/250 = 0.1
1. Butan – 2 – ol √ ½
2. 4 – methylhex – 2- ene √
3. Propyl ethnoate √
1. Soap less detergent √
2. Non- biodegradable resulting in pollution √
2. Addition
1. A – Sodium ethanoate
  B – Acidified KMnO₄ or K₂Cr₂O₇
2. Oxidation
1. NH_3(g) + HNO_3(aq) → NH₄NO_3(s)
2. 17 kg ammonia = 80kg NH₄NO₃ (½)
  ∴5.3kg =?
  80 x 5.3 = 24.94Kg (1½)
  17
1. A reaction between an ethanol and alkanoic acid to form ester;
2. 2. Ethylpentanoate . √1
1. ethylethanoate√ ½
  CH₃ - H₂C- O-C-CH₃ √ ½
2. step 2: oxidation √ ½
  step 4: esterification √ ½
3. sodium hydroxide ,or NaoH√1
1. Hydrogen. √1
2. 1. A No effervescence takes place. √½
  2. B There is effervescence √½ and the gas produced turns lime water into white precipitate.√½
1. Y √1
2. Z and W √1 have same atomic number but different mass number. √1
1. Insulators
2. Are non-conductor since they lack delocalised electrons
1. Soapless detergent
2. Non-biodegradable
1. No. of half –lifes (n) = 120 = 6
  20
  Y x (½)⁶ = 3.5
  Y = 3.5 x 26
  Y = 224g
  (all steps for equation )
  OR:
2. – To study the rate of absorption of fertilizer by plants using radioactive phosphorous
  - Tracing chemical and physiological processes such as photosynthesis
  - Sterilizing equipment (1ny one )
1. Polypropene
2. (H₂C= CH – CH₃)n = 4956
  (12 x 3) + (6x1) = 36 + 6 = 42 (molecular mass of 1 unit)
  no. of units = 42n = 495
  42n = 4956
  42n = 4956
  42 42
  n = 118
1. RCOONa⁺ Soapy detergent
  R CH₂OSO_3^-Na+ soap less detergent
2. RCH₂OSO₃^-Na⁺ does not form scum. Its calcium and magnesium salts are soluble
3. Chlorine bleaches by oxidation
  SO₂ bleaches by reduction
1. Polyphenylethene