KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
a) Write a nuclear equation for the decay process of carbon -14.
b) From the graph, determine the; i) Half-life of carbon -14; ii) Percentage of carbon -14 in a sample whose age is 1950 years.
0 Comments
The curve below represents the changes in the concentration of substance E and F with time
In the reaction; E (g) ⇄ F(g)
(i) Which curve represents the changes in concentration of substance F? Give a reason
(ii) Give a reason for shapes of curves after time ‘t’ minutes
Use the information below to answer the question that follows
Use the cell representation below to answer the questions that follow
Complete the table below by writing the product formed at the electrodes during the electrolysis of the electrolytes given in the table.
What is the name given to each of the following:
Iron is obtained from haematite using a blast furnace shown if figure 5 below.
a) Four raw materials are required for the production of iron. Three of these are iron oxide, hot air and limestone
Give the name of the fourth raw material b) Write an equation for the reaction in which carbon (IV) oxide is converted into carbon (II) oxide. c) Explain why the temperature in the region marked Y is higher than that of the incoming hot air. d) State one physical property of molten slag other than density that allows it to be separated from molten iron as shown in figure 5. e) One of the components of the waste gases is Nitrogen (IV) oxide describe the adverse effects it has on the environment. f) Iron from the blast furnace contains about 5% carbon i) Describe how the carbon content is reduced. ii) Why is it necessary to reduce the carbon content?
ANSWERS
(a) Coke/ coal/ Charcoal/ Carbon
(b) C(s) + CO2 (g) → 2 CO(g) (c) The reaction between coke/ coal and the hot air is highly exothermic (d) Slog is immiscible with molten iron (e) Nitrogen (iv) oxide gas forms acid rain. Which corrodes metallic materials and destroys vegetation the environment. (f) (i) By passing/ blowing oxygen into molten iron which converts carbon into carbon (iv) Oxide (ii) To increase the tensile strength/ making the iron less brittle/ making it more malleable / making it more ductile.
a) Study the table below and complete it. (W-1 and X4+ are not the actual symbols of the ions).
b) State the observation that would be made in the following tests to distinguish between:
i) Sodium and copper burning pieces of each in air. ii) Sodium and Magnesium by placing small pieces of each in cold water which contains two drops of phenolphalein. c) The atomic numbers of Na and Mg are 11 and 12 respectively. Which of the elements has a higher ionization energy? Explain. d) Naturally occurring uranium consists of three isotopes which are radioactive.
i) Which of these isotopes has the longest half-life? Give a reason
ii) Calculate the relative atomic mass of uranium
(iv)State one use of radioactive isotopes in the paper industry
ANSWERS
(b) (i) Sodium burns with a yellow flame & yellow white/ solid powder is formed while copper burn with a blue green flame & black powder/ silic is formed.
(ii) Sodium darts on the surface of water / rapid fast effervescence (fast production of bubbles; solution becomes pink immediately. Magnesium sinks in water/ slow (production of bubbles) effervescence/ solution becomes pink gradually. (c) Magnesium it has a higher nuclear charge which pulls outer electrons more strongly
State the observation that would be made when a piece of sodium metal is placed in samples of:
Pentane: __________ Pentanol: __________
The table below shows the solubility of a salt at various temperatures
What would happen if a sample of a saturated solution of the salt at 400C is heated to 800C. Explain
(a)Figure 3 show the changes that take place between states of matter. Some of them have been identified and others labelled.
i) Give the names of the processes
I H II G ii) Name one substance that can undergo process F when left in an open container in the laboratory. iii) The process J is called deposition. Using water as an example, write an equation that represents the process of deposition. b) Figure 4 shows the beating curve for water.
i) Give the names of the intermolecular forces of attraction in the segments;
I MN II RS ii) The heats of fusion and vaporization of water are 334.4 Jg-1 and 1159.4 Jg-1 respectively. I Explain why there is a big difference between the two. II How is the difference reflected in the curve? c) Coal, oil and natural gas are major sources of energy. They are known as fossil fuels. Hydrogen is also a source of energy. i) State and explain two reasons why hydrogen is a very attractive fuel compared to fossils. ii) State one disadvantage of using hydrogen fuel instead of fossil fuels.
ANSWERS
(a)
(i) I. Condensation II. Melting (ii) Iodine, Benzoic acid, Camphos, Dry Ice. Solid CO2 Naphthalene (iii) H2O(g) →H2O(g) (b) (i) Van des waals and hydrogen bonding II Van des waals forces (ii)I. The separation distance is smaller during fusion than during vaporization hence requires much lower energy than in vaporization and vice versa. II. Heating time NP is far much less than heating time in QR/ Heating time (c) (i) Hydrogen burns to produce steam which is a non pollutant/ does not cause pollution to the environment Hydrogen has a high energy content hence very small amount produce a lot of heat energy Hydrogen is renewable hence cannot be exhausted/ used completed. (ii) It can easily explore when burning/ highly flammable unlike fossils fuels expensive.
The set-up below (figure 2) was used to electrolyse a bromide of metal D DBr2
i) Write equation for the reactions at the
I cathode II anode ii) The electrodes used in the experiment were made of carbon and metal D. which of the two electrodes was used as the anode? Give a reason. iii) Give a reason why this experiment is carried out in a fume cupboard. iv) When a current of 0.4A was passed for 90 minutes, 2.31 g of metal D were deposited. I Describe how the amount of metal D deposited was determines. II Calculate the relative atomic mass of metal D. (I Faraday = 96500 coulombs)
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 the conditions necessary for the reaction in step (IV)
ANSWERS
(b)
Starting with red roses, describe how;
(i) a solution containing the red pigment may be prepared (ii) the solution can be shown tobe an indicator.
ANSWERS
(i)Crush the roses with a suitable solvent Filter to obtain pigment
(ii)Add pigment to an acid . It turns read
Study the flow chart below and answer the questions that follow
(a) Name:
Aluminium metal is a good conductor and is used for overhead cables. State any other two properties that make aluminium suitable for this use.
(a) The following equations represents two different types of reactions
(i) nC4H8(g) → (C4H8)n(s) (ii) C2H6(g) + CI2(g) → C2H5CI(I) + HCI(g) State the type of reaction represented by: (i) (ii) (b) The fermentation of glucose produces ethanol as shown in the equation below C2H12O6(aq) → 2CH3CH2OH(aq) + 2CO2(g)
(c) The molecular formula of a hydrocarbon is C6H14. The hydrocarbon can be converted into two other hydrocarbons as shown by the equation below (i) Name and draw the possible structural formula of X Name Structural formula (ii) State and explain the observation that would be made if a few drops of bromide water were added to a sample of X. (iii) Write an equation for the complete combustion of C3H8 In order to determine the molar of neutralization of sodium hydroxide, 100cm3 of 1M sodium hydroxide and 100cm3 of 1 M hydrochloric acid both at the same initial temperature were mixed and stirred continuously with a thermometer. The thermometer of the resulting solution was recorded after every 30 seconds until the highest temperature of the solution was attained. Thereafter the temperature of the solution was recorded for a further two minutes
(a)
I. What is the significance of point Y2? II. Explain why there is a temperature change between points; Y1 and Y2 Y3 and Y4 (iv) In the initial temperature for both solutions was 24.50C and the highest temperature attained by the mixture was 30.90C Calculate the: I. heat change for the reaction (specific heat capacity of the solution = 4.2Jg -1K-1 and the density of the solution = 1.0g/cm3 II. Molar heat of neutralization of sodium hydroxide (v) Explain how the value of the molar heat of neutralization obtained in this experiment would compare with the one that would be obtained if the experiment was repeated using 100cm3 of 1 Methanoic acid instead of hydrochloric acid. (b) On the grid provided below, draw an energy level diagram for the reaction between hydrochloric acid and sodium hydroxide
ANSWER
(a) Energy of the activated energy Therefore more molecules will take part in effective collision. Or Energy of the activated/intermediate complex of the unanalyzed reaction
(b) Catalyst lowers the activation energy therefore more molecules will take effective collision
ANSWERS
For each of the following reactions, state the observation and write the formula of the
Compound responsible for the observation: a) Bromine water is added to aqueous potassium iodide; b) Excess aqueous ammonia is added to copper (II) hydroxide (precipitate).
ANSWERS
(a) Pale green solution turns yellow
(b) Sodium hydroxide Potassium hydroxide (c) Water |
Chemistry Topics
All
Archives
December 2024
|
We Would Love to Have You Visit Soon! |
Hours24 HR Service
|
Telephone0728 450425
|
|
8-4-4 materialsLevels
Subjects
|
cbc materialsE.C.D.E
Lower Primary
Upper Primary
Lower Secondary
Upper Secondary
|
teacher support
Other Blogs
|