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​These are chemistry questions and answers categorized according to topics, papers i.e. Paper 1 and 2, Levels i.e. form 1 to form 4, kcse year the examination was done and section A or B
Select topic/category to open topical questions from that particular option provided. ​Chemistry Topics
The following set – up was made in an experiment by a group of form four students. The readings of the balance before and after experiment were indicated in the diagram below. Given that the initial temperature of water was 26.7 degrees centigrade respectively. The specific heat capacity of water is 4200Jkg-1k-1
Determine:a) Temperature change that occurred (1mk)
b) Amount of ethanol used (1mk)
10.5 – 1.0 = 9.5g
c) Moles of ethanol used (2mks)
d) Amount of heat gained by water (2mks)
e) Molar enthalpy of combustion of ethanol (2mks)
f) Use the following thermochemical processes to answer the questions that follow;
i) Draw an energy level diagram representing the formation and combustion processes of propane, carbon and hydrogen (2mks)
ii) Hence or otherwise, determine the heat of formation of propane (2mks)
The empirical formula of a hydrocarbon is (CH2). It has a density of 0.001167g/cm3 at room temperature and pressure. (Molar gas volume at r.t.p is 24dm3)a) Determine the molecular formula of the hydrocarbon (3mks)
b) Draw the structural formula of the hydrocarbon (1mk)
c) Ethene gas burns in Oxygen to form Carbon (IV) oxide and water.i) Write an equation for the reaction between ethane gas oxygen gas (1mk)
ii) 15cm3 of ethene gas were mixed with 50cm3 of oxygen gas and the mixture was ignited into complete combustion. Calculate the volume of excess unreacted gas (3mks)
d) What happens when ethene gas is bubbled through bromine water? (2mks)
e) Give any two uses of ethene gas (2mks)
Uses of Ethene gas
Use the information below to answer the questions that follow Ethanol is formed as shown below11/10/2021 Use the information below to answer the questions that follow Ethanol is formed as shown below
Draw the energy cycle diagram and for the formation and combustion of ethanol and calculate the heat of formation of ethanol (3mks)
a) Give a reason why ethanoic acid has a higher boiling point than ethanol which has the same number of Carbon atoms (1mk)
Ethanoic acid form hydrogen bond which are stronger than those in ethanol
b) Draw the structural formula of ethanoic acid (1mk)
The diagram in figure I shows some natural and industrial processes. Study it and answer the questions that follows
(a) Identify the processes labelled:
A................... B................... C................... D................... (b) State the reagents and conditions required for processes B and D. (i) Process B: Reagent................ Conditions ............ (ii) Process D: Reagent................ Conditions ............ (iii) Describe how process D is carried out. (iv) State two additives used to improve the quality of soap. (c) State the reagents required in steps F and G. (iii) Draw the structure of terylene. (d) (i) Name the polymer formed in step C. (ii) State one disadvantage of the polymer formed in (d) (i).
ANSWERS
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).
ANSWERS
The conductivity of some substances was investigated. The observations made were recorded in
Table 1. Use it to answer the questions that follow. 
(a) (i) Identify a substance that is a metal. Give a reason.
(ii) Substance F does not conduct electricity in solid state but conducts in molten or aqueous state. Explain. (b) Copper(II) sulphate solution was electrolysed using the set up in Figure 1. 
(i) State the observations made during electrolysis.
(ii) Write the equation for the reaction that occurs at the anode. (iii) State the expected change in pH of the electrolyte after electrolysis. (c) The experiment was repeated using copper electrodes instead of carbon electrodes. Describe the observations made at each electrode. (d) Electroplating is an important industrial process. What is meant by electroplating. (iii) During electroplating of an iron spoon, a current of 0.6 amperes was passed through aqueous silver nitrate solution for 1 1/2 hours. Calculate the mass of silver that was deposited on the spoon. (Ag = 108.0 ; I F = 96,500 C /mol)
ANSWERS
(a)(i) G — Contains delocalized electrons present in solid and molten state.
(ii) In solid state, the ions are rigidly held in position and cannot move, hence will not conduct. In molten/aqueous state, the ions are mobile and will be able to conduct electric current. (b)(i)The blue electrolyte fades and finally changes from blue to colourless, Effervescence / bubbles of a colourless gas. A brown deposit forms on the cathode. 
(c) With copper electrodes:
Anode will go into solution as copper ions hence it decreases in mass/size. Brown deposit forms at the cathode hence the cathode increases in mass. (d) (i) This is the coating of an article / object with another metal by electrolytic method /electrolysis. 
(a) Name the homologous series represented by each of the following general formulae.
(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 the use of the sodium salt. (c) Ethyne is the first member of the alkyne family. (i) Name two reagents that can be used in the laboratory to prepare the gas. (ii) Write an equation for the reaction. (d) Perspex is an addition synthetic polymer formed from the monomer, 
(i) What is meant by addition polymerisation?
(ii) Draw three repeat units of perspex. Give one use of perspex (iv) State two environmental hazards associated with synthetic polymers.
ANSWERS
They are non-biodegradable hence pollutes the environment. Accelerates fires when burned / highly flammable.
a)Draw the structural formula for all the isomers of C2H3CL3
b) Describe two chemical tests that can be used to distinguish between ethane and ethane.
c)The following scheme represents various reactions starting with propan-1-ol. Use it to answer the questions that follow. 
i) Name one substance that can be used in step I.
ii) Give the general formula of X. 
iii)Write the equation for the reaction in step IV.
iv) Calculate the mass of propan-1-ol which when burnt completely in air at room temperature and pressure would produce 18dm3 of gas. (C = 12.0; O = 16.0; H = 1.0; Molar gas volume = 24dm3)
ANSWERS
1.
(a) Alkanes are said to be saturated hydrocarbons.
(b) When the alkane, hexane, is heated to high temperature, one of the products is ethene.
Expected Response
Related Chemistry Questions and Answers on Organic Chemistry II Form 3 Level
(a)Draw the structure of compound N formed in the following reaction.
(b) Give one use of compound N.
ANSWERS
(b) Making synthetic fibres such as for: - Ropes
Blouses Stockings Undergarments Trousers
An alknal has the following composition by mass: hydrogen 13.5%, oxygen 21.6% and carbon 64.9%
(a)Determine the empirical formula of the alcohol(C=12.0; H=1.0’ 0=16.0). (b)Given that empirical formula and the molecular formula of the alkanol are the same,draw the structure of the alkonol
ANSWERS
(b) When magnesium burns in air, it forms a white solid and a grey-green solid.
When a few drops of water are added to the mixture, a gas that turns red litmus paper blue is evolved. Identify the (i) white solid. (ii) gas evolved and state its use. (I) Name of gas (II) Use of the gas. ; (c) Two different samples of water (I and II) were tested with soap solution. Sample II was further subjected to two other processes before adding soap. 20 cm3 of each sample of water was shaken with soap solution in a boiling tube until a permanent lather was obtained. The results are shown in the table below 
(i) Identify the water sample that had temporary hardness. Explain your answer.
(ii) Explain why the results for sample II are different after distilling but remain unchanged after filtering. (iii) State two disadvantages of using both water samples for domestic purposes.
ANSWERS
(i) - Water sample with temporary hardness is I
- It uses less soap after boiling 
(a) Draw the structure of the folio wing 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 manganate (VII) Were added to oil obtained from nut seeds? Explain. (d) State one method that can be used to convert liquid oil from nut seeds into solid. (e) Describe how soap is manufactured from liquid oil from nut seeds (f) 0.44 g of an ester A reacts with 62.5 cm3 of 0.08 M potassium hydroxide giving an alcohol Band substance C. Given that one mole of the ester reacts with one mole of the alkali, calculate the relative molecular mass of the ester.
ANSWERS
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AuthorMaurice Atika is a teacher and a netprenuer. |
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