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Form 4 Chemistry Organic Chemistry II Questions and Answers
Describe two chemical tests that can be used to distinguish ethanol from ethanoic acid.
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1.
(a)Name one natural fibre. (b)Give one advantage of synthetic fibres over natural fibres.
2.
A compound #C_4H_10O# is oxidized by excess acidified potassium manganate (VII) to form another compound #C_4H_8O_2#.The same compound #C_4H_10O# reacts with potassium to produce hydrogen gas. (a)Draw the structural formula and name the compound #C_4H_10O# (b)Write an equation for the reaction between potassium and compound #C_4H_10O#.
3.
Explain how a sample of #CH_3CH_2CH_2OH#, could be distinguished from a sample of #CH_3COOH# by means of a chemical reaction.
4.
A compound whose structure is shown below is found in a detergent. With reference to the structure, explain how the detergent removes grease during washing.
5.
A polymer has the following structure: A sample of this polymer if found to have a molecular mass of 5194. Determine the number of monomers on the polymer (H=1.0, C=12.0, N=14.0)
6.
A mixture of pentane and pentanoic acid was shaken with 0.1 M sodium hydroxide solution and let to separate as shown in the diagram below: Name the main component in layer W. Give a reason for the answer. Answer: This is because pentanoic acid reacts with sodium hydroxide leaving pentane which is neutral.
7.
Study the table below and answer the questions that follow: (i)Which of the compounds is a solid at #10.0^0#C? Explain. (ii) Choose two compounds which are members of the same homologous series and explain the difference in their melting points.
8.
The structures shown below represent two cleansing agents, A and B Which cleansing agent would be more suitable for washing in water containing magnesium sulphate? Give a reason.
9.
Give the names of the following compounds: (i)#CH_3CH_2CH_2CH_2OH# (ii)#CH_3CH_2COOH# (b)Study the information in the table below and answer the questions (i)Write the general formula of the hydrocarbon in the table (ii) Predict the relative atomic mass of the hydrocarbon with 5 carbon atoms. (iii)Determine the molecular formula of the hydrocarbon in (ii) above and draw its structural formula
10.
(a)Draw the structural formula of: (i) Ethanol (ii) Propanoic (b) Give the name of the organic compound formed when ethanol and propanoic acid react in the presence of concentrated sulphuric (VI) acid
11.
(a)The following equations represents two different types of reactions (i)#nC_4H8_((g)##rightarrow # (#C_4H_8)n# (s) (ii)# C_2H_6 (g)# +#Cl_2# (g)#overset(U.V)(rightarrow)# #C_2H_5Cl# (l)+ HCl (g) State the type of reaction represented by: (i) and (ii). (b)The fermentation of glucose produces ethanol as shown in the equation below:
12.
State the observation that would be made when a piece of sodium metal is placed in samples of: (i)pentane (ii) pentanol
13.
(a)When an organic compound Y is reacted with aqueous sodium carbonate, it produces carbon (IV) oxide. Y reacts with propanol to form a sweet smelling compound Z whose formula is. (i) Name and draw the structural formula of compound Y. (ii) What is the name of the group of compounds to which Z belongs? (b) In an experiment, excess ethanol was warmed with potassium dichromate for about twenty
14.
Pentane and ethanol are miscible. Describe how water could be used to separate a mixture of pentane and ethanol
15.
(a)In which homologous series do the following compounds belong (i)#CH_3#CCH (ii) #CH_3CH_2#COOH (b)Raw rubber is heated with sulphur in the manufacture of natural rubber (i)What is the name given to the process? (ii) Why is the process necessary? (c ) Study the scheme given below and answer the questions that follow. (i) Write an equation for the reaction between propan-1-Ol and potassium metal.
16.
The structure below represents a portion of a polymer. Give: (a)the name of the polymer. (b) One industrial use of the polymer
17.
(a)Write the structural formula of: (i) Methanol. (ii)Methanoic acid. (b)Write the equation for the reaction between methanoic acid and aqueous sodium hydroxide. (c )(i) Name the product formed when methanol reacts with methanoic acid. (ii)State one condition necessary for the reaction in (c ) (i) above to take place. (d)(i) Describe one chemical test that can be used to distinguish between hexane
18.
(a)Give the names of the following compounds (i)# CH_3CH=CHCH_2CH_3# (b) Ethane and Ethene react with bromine according to the equation given below. (i)#C_2H_6(g)# +#Br_2 (g)##to##C_2H_5Br_2 (g)#+ HBr (g) (ii) #C_2H_4 (g)# +#Br_2 (g)# #to##C_2H_4Br_2 (l)# Name the type of bromination reaction that takes place in: (i) and (ii). (c)Study the diagram below and answer the questions that follow.
19.
(a) What is meant by heat vaporization. (b) The boiling points of ethanol, propanol and butanol are #78^oC#, #97.2^oC# and #117^oC#. Explain this trend.
20.
An organic compound with the formula #C_4H_10O# reacts with potassium metal to give hydrogen gas and white solid. (a) Write structural formula of the compound. (b) To which homologous series does the compound belong? (c) Write the equation for the reaction between the compound and potassium metal.
21.
(a) State how burning can be used to distinguish between ethane and ethyne. Explain your answer. (b) Draw the structural formula of the third member of the homologous series of ethyne. (c) The flow chart below shows a series of reactions starting with ethanol. Study it and answer the questions that follow (i) Name I.process A II.Substances B and C (ii) Write the equation for the combustion of
22.
Study the information in the table below and answer the questions that follow. Give a reason why the difference in the molar heats of combustion between successive alcohols are close.
23.
(a) The list below shows the formulae of some organic compounds. Use it to answer the questions that follow. (i) Select two compounds which: I.are not hydrocarbons II.belong to the same homologous series. (ii) Identify the compound that is likely to undergo polymerization. Give a reason for your answer. (b) The structures below represent two cleansing agents: #R-COO^(-)Na^(+)# #R-OSO_3^(-)Na^(+)#
24.
Explain why the boiling point of ethanol is higher than that of hexane. (Relative molecular mass of ethanol is 46 while that of hexane is 86)
25.
(a) What name is given to a compound that contains carbon and hydrogen only? (b) Hexane is a compound containing carbon and hydrogen. (i) What method is used to obtain hexane from crude oil? (ii) State one use of hexane. (c) Study the flow chart below and answer the questions that follow. (i) Identify reagent L . (iii) Draw the structural formula of gas J (iv) What name is given to the process
26.
(a) Name the process that takes place when: (i) Crystals of zinc nitrate change into solution when exposed to air. (ii) An alcohol reacts with an organic acid in the presence of a catalyst to form a sweet smelling compound. b) Propane can be changed into methane and ethane as shown in the equation below; #CH_3CH_2CH_3(g) overset(high.temp)(to) CH_4(g)+C_2H_4(g)# Name the process undergone by
27.
An alkanol has the following composition by mass:hydrogen 13.5%, oxygen 21.6% and carbon 64.9% (a) Determine the empirical formula of the alkanol (C=12.0;H=1.0;O=16.0). (b) Given that empirical formula and the molecular formula of the alkanol are the same, draw the structure of the alkanol.
28.
The table below shows the relative molecular masses and the boiling points of pentane and propan-1-ol. Explain why the boiling point of propan-1-ol is higher than that of pentane.
29.
The structure of a detergent is (a) Write the molecular formula of the detergent. (b) What type of detergent is represented by the formula? (c) When this type of detergent is used to wash linen in hard water, spots(marks) are left on the linen. Write the formula of the substance responsible for the spots.
30.
The structure below represents a sweet smelling compound. Give names of the two organic compounds that can be used to prepare this compound in the laboratory.
31.
(a) Alkanes, alkenes and alkynes can be obtained from crude oil. Draw the structure of the second member of the alkyne homologous series. (b) Study the flow chart below and answer the questions that follow (i) State the conditions for the reaction in step I to occur. (iii) Give: I.One disadvantage of the continued use of substance such as J. II.The name of the process that takes place in step III
32.
(a) Draw the structure of compound N formed in the following reaction (b) Give one use of compound N.
33.
(a) Draw the structures of the following compounds: (i) 2-methylbut-2-ene; (ii) Heptanoic acid (b) Describe a physical test that can be used to distinguish between methanol and hexanol (c) Use the flow chart below to answer the questions that follow (i) Name: I.the type of reaction that occurs in step II; II.substance B (ii) Give the formula of substance C. (iii) Give the reagent and conditions
34.
Some animal and vegetable oils are used to make margarine and soap. Give the reagents and the conditions necessary for converting the oils into: (a) Margarine; (b) Soap.
35.
The use of CFCs has been linked to depletion of the ozone layer. (a) What does CFC stand for? (b) State another environmental problem caused by CFCs.
36.
(a) Give the names of the following compounds: (b) Describe a chemical test that can be carried out in order to distinguish between. (c) Study the flow chart below and answer the questions that follow. (i) Name the compounds: (I) L (II) N (ii) Draw the structural formula of compound M showing two repeat units. (iii) Give the reagent and the condition used in step I. (iv) State the type of reaction
37.
(a) What name is given to the process by which alcohol is formed from a carbohydrate? (b) Explain why solubility of ethane in water is lower than that of ethanol.
38.
Two organic compounds Pand Q decolourise acidified potassium manganite (VII) solution; but only P reacts with sodium metal to give a colourless gas. Which homologous series does compound P belong? Give a reason.
39.
(a) Study the flow chart below and answer the questions that follow. (i) I.what is observation will be made in step I? II.Describe a chemical test that can be carried out to show the identity of compound C. (ii) Give the name of the following: I.E II.substance D (iii) Give the formula of substance B iv) Name the type of reaction that occurs in: I.step (II)
40.
Give two uses of the polymer polystyrene.
41.
Describe two chemical tests that can be used to distinguish ethanol from ethanoic acid.
42.
(a) Give the systematic names for the following compounds: (b) Study the flow chart below and use it to answer the questions that follow: (i) Identify the organic compound K. (ii) Write the formula of M. (iii) Give one reagent that can be used in: (I) Step I (II) Step II. (iv) Write the equation of the reaction in step III
43.
The table below shows the relative molecular masses and boiling points of pentane and ethanoic acid. Explain the large difference in boiling between ethanoic acid and pentane.
44.
Study the flow chart below and answer the questions that follows. (a) Name the process in step I (b) Identify the reagent in step II (c) Give one use of ethane
45.
Cotton is natural polymer. State one advantage and one disadvantage of this polymer.
46.
(a) Draw the structures of the following: (i) Butan-1-ol (ii) Hexanoic acid. (b) Study the flow chart below and answer the questions that follow. (i) State the conditions necessary for fermentation of glucose to take place (ii) State one reagent that can be used to carry out process S (iii) Identify gases P and T (iv) How is sodium hydroxide kept dry during reaction? (v) Give one commercial use of
47.
(a) Give the name of the first member of the alkene homologous series. (b) Describe a chemical test that can be used to distinguish butanol from butanoic acid.
48.
Study the flow chart below and use it answer the questions that follow. (a) Name process T. (b) Give the formula of W. (c) State two uses of X.
49.
(a) Draw the structure of the following compounds. (i) Butanoic acid; (ii) Pent-2-ene (b) Explain why propan-1-ol is soluble in water while prop-1-ene is not. (Relative molecular mass of propan-1-ol is 60 while that of prop-1- ene is 42). (c) What would be observed if a few drops of acidified potassium manganite (VII) were added to oil obtained from nuts seeds? Explain. (d) State one method that
50.
An alkanol has the following composition by mass:hydrogen 13.5%, oxygen 21.6% and carbon 64.9% (a) Determine the empirical formula of the alkanol (C=12.0;H=1.0;O =16.0). (b) Given that empirical formula and the molecular formula of the alkanol are the same, draw the structure of the alkanol.
51.
(a) Draw the structure of compound N formed in the following reaction. (b) Give one use of compound N.
52.
Study the flow chart in figure 5 and answer the questions that follow. (a) Identify substances k and L. (b) Name one reagent that can be used to carry out process J.
53.
When an aqueous solution of compound X was mixed with few drops of bromine water, the colour of the mixture remained yellow. When another portion of solution X was reacted with acidified potassium dichromate (VI), the colour of the mixture changed from orange to green. (a) What conclusion can be made from use of: (i) Bromine water? (ii) Acidified potassium dichromate (VI)? (b) Solution X was react
54.
(a) Name the homologous series represented by each of the following general formulae. (i) #C_nH_(2n-2_# (ii) #C_nH_2n# (b) Compound G is a trimester. (i) Give the physical state of compound G at room temperature. (ii) G is completely hydrolysed by heating with aqueous sodium hydroxide. I.Give the structural formula of the alcohol formed. II.Write a formula for the sodium salt formed. III.State
55.
The following are formulae of organic compounds. Use the formulae to answer the questions that follow: (a) Select: (i) Two compounds which when reacted together produce a sweet smelling compound. (ii) An unsaturated hydrocarbon. (b) Name the compound selected in (a) (ii).
56.
The diagram in figure 1 shows some natural and industrial processes. Study it and answer the questions that follow. (a) Identify te processes labeled A,B,C,D. (b) State the reagents and conditions required for processes B and D. (i) Process B: (ii) Process D: (iii) State two additives used to improve the quality of soap. (c) State the reagents required in steps F and G. (i) F (ii) G
57.
(a) Alkanes are said to be saturated hydrocarbons. (i) What is meant by saturated hydrocarbons. (ii) Draw the structure of the third member of the alkane homologous series and name it. (b) When the alkane, hexane,is heated to high temperature, one of the products is ethane. (i) Write the equation for the reaction. (ii) Name the process described in (b). (c) Study the flow chart in figure 1 and
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