KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
State and explain the observation that would be made when a few drops of concentrated sulphuric acid are added to a small sample of hydrated copper (II) sulphate
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The flow chart below shows the industrial preparation of ammonia and the process used in the manufacture of some ammonium compounds. Study and answer the questions that follow
(a) Give the name of the
(c) Explain why it necessary to compress nitrogen and hydrogen in this process (d) Write an equation for the reaction which takes place in step 6 (e) Name the catalyst and the reagents used in step 3 Catalyst Reagent (f) Name compound Z1 (g) Give one commercial use of compound Z2
(a) An ore is suspected to contain mainly iron. Describe a method that can be used to confirm the presence of iron in the ore
(b) Excess carbon monoxide gas was passed over a heated sample of an oxide of iron as shown in the diagram below. Study the diagram and the data below it to answer the questions that follow.
Mass of empty dish = 10.98g
Mass of empty dish 4 oxide of iron = 13.30g Mass of empty dish 4 residue = 12.66g
(c) Corrosive is a destructive process in which iron which is converted into hydrated iron (III) oxide State:
(d) Explain why it is not advisable to wash vehicles using seawater
ANSWERS
(a) Temperature and pressure are directly proportional (l) IR words towards that of real
(b) With increase in temperature, the gas particles gain more Kinetic energy They move faster and collide with the walls of the container more frequently hence increasing pressure.
The figure below represents the set up that was used to crack an alkane.
a) What was the purpose of the sand?
b) After some time, a colourless gas G collected in the test-tube. Describe a chemical test and the observations that would be made in ordered to identify the class of compounds to which gas G belongs.
ANSWERS
(a) Catalyst or words to that effect
(b) Add bromine water or acidified potassium magnate (VII) if they decolorize then gas is either an alkene or an alkynes What is the oxidation number of chlorine in CO4
Expected Response
A hydrocarbon slowly decolorizes bromine gas in the presence of sunlight but does not decolourise acidified potassium permanganate
Name and draw the structural formula of the fourth member of the series to which the hydrocarbon belongs.
Expected Response
a) Draw and name the structure of the compound formed when one mole of ethyne reacts with one mole of hydrogen bromide.
b) Draw the structures of the alkynes whose molecular formula is C4H6
A sealed glass tube containing air at s.t.p was immersed in water at 1000c. Assuming that there was no increase in the volume of the glass tube due to the expansion of the glass, calculate the pressure of the inside tube.
(standard pressure = 760mmHg,)
Expected Response
The formula given below represents a portion of a polymer Give:
Expected Response
The diagram below represents a charcoal burner. Study it and answer the questions that follow
Write equations for the reactions taking place at I and I and II
Expected Response
Urea, (NH2)2CO is prepared by the reaction between ammonia and carbon dioxide. 2NH3(g) + CO2(g) → (NH2)2CO(aq) + H2O(l). In one process, 680 kg of ammonia were reacted with excess carbon dioxide. Calculate the mass of urea that was formed. (H = 1.0, c+ 12.0, N =14.0, O = 16.0 and relative molecular mass of ammonia = 17) Calculate the mass of Urea that was formed
Expected Response
(a) Describe the process by which Nitrogen is obtained from air on a large scale.
(b) Study the flow chart below and answer the questions that follow.
(i) Identify gas J.
(ii) Using oxidation numbers, show that ammonia is the reducing agent in step (VI) (iii) Write the equation for the reaction that occurs in step (V). (iv) Give one use of ammonium nitrate. c) The table below shows the observations made when aqueous ammonia was added to cations of elements F2F and G until in excess.
(i) Select the cation that is likely to be Zn2+
(ii) Given that the formula of the cation of element E is E 2+, write the ionic equation for the reaction between E2+ (aq) and aqueous ammonia.
Crude oil contains sulphur. What would be the effect to the environment of using fuel containing sulphur?
ANSWERS
In an experiment to determine the percentage of magnesium hydroxide in an anti-acid, a solution containing 0.50 g of the anti-acid was neutralized by 23.0 cm3 of 0.010m hydrochloric acid (Relative formula mass of magnesium hydroxide =58)
a) Mass of magnesium hydroxide in the anti-acid; b) Percentage of magnesium hydroxide in the anti-acid
a) State the Graham's law diffusion.
b) The molar masses of gases W and X are 16.0 and 44.0 respectively. If the rate of diffusion of W through a porous material is 12cm3s-1 calculate the rate of diffusion of X through the same material. ​Related Chemistry Questions and Answers on Gas Laws Form 3 Level
In an experiment, a test-tube full of chlorine water was inverted in chlorine water as shown in the diagram below and the set up left in sunlight for one day.
After one day, a gas was found to have collected in the test-tube
a) Identify the gas. b) What will happen to the PH of the solution in the beaker after one day? Give an explanation.
On complete combustion of a sample of hydrocarbon, 3.52 gm of carbon dioxide and 1.44 gm of water were formed. Determine the molecular formula of the hydrocarbon.
(Relative molecular masses of hydrocarbon = 56, carbon dioxide 44, water = 18 and relative atomic masses H = 1.0 and c = 12.0)
When magnesium was burnt in air, a solid mixture was formed. On addition of water to the mixture a gas which turned moist red litmus paper blue was evolved. Explain these observations.
Zinc reacts with both concentrated and dilute sulphuric (VI) acid. Write equations for two reactions.
a) State the observation made at the end of the experiment when a mixture of iron powder and sulphur is heated in a test tube.
b) Write an equation for the reaction the product in (a) above and dilute hydrochloric acid. c) When a mixture of iron powder and sulphur is heated, it glows more brightly than that of iron fillings and sulphur. Explain this observation
Phosphoric acid is manufactured from calcium phosphate according to the following equation.
Ca3(PO4)2(s) + 3H2SO4(l) → 2H3PO4(aq) + 3 CaSO4(s) Calculate the mass in (Kg) of phosphoric acid that would be obtained if 155 Kg of calcium phosphate reacted completely with the acid (Ca=40, P=31, S=32, O=16, H=1) |
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