KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
Sulphur(IV) oxide is prepared in the laboratory using the set-up in Figure 3. Study it and answer the questions that follow.
(a) Identify substance F. (1 mark)
(b) Write an equation for the reaction that takes place in the flask. (1 mark) (c) State the purpose of liquid G. (I mark)
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Table 1 shows the properties of two chlorides, D and E.
(a) State the type of bond present in:
A solution contains 40.3 g of substance XOH per litre. 25M cm3 of this solution required 30.0cm3 of 0.3 M sulphuric(Vl) acid for complete neutralisation. (a) Calculate the number of moles of XOH that reacted. (½ mark) (b) Determine the relative atomic mass of X. (1½ marks)
A farmer intended to plant cabbages in his farm. He first tested the pH of the soil and found it to be 3.0. If cabbages do well in alkaline soils, explain the advice that would be given to the farmer in order to realise a high yield. (2 marks)
Hydrogen gas can be prepared by passing steam over heated magnesium ribbon as shown in Figure 2.
(a) Write an equation for the reaction that produces hydrogen gas. (1 mark)
(b) Explain why the delivery tube must be removed from beneath the water before heating is stopped. (1 mark) (c) Explain why sodium metal is not suitable for this experiment. (1 mark)
A monomer has the following structure.
(a) Draw the structure of its polymer that contains three monomers. (1 mark)
(b) A sample of the polymer formed from the monomer has a molecular mass of 4992. Determine the number of monomers that formed the polymer (C= 12; H= 1.0). (2 marks)
(a) The set up below was used to prepare dry hydrogen chloride gas, and investigate its effect on heated iron filings.
(i). Name substance L
(ii) Name liquid M (iii) What will be observed in tube B? (iv) Write an equation for the reaction that occurs in tube B. (v) Why is the gas from tube B burnt? (b) (i) Explain the following observations: I) A white precipitate is formed when hydrogen chloride gas is passed through aqueous silver nitrate. II) Hydrogen chloride gas fumes in ammonia gas. (ii) State two uses of hydrogen chloride gas (c) The diagram below is a representation of an industrial process for the manufacture of a bleaching powder.
(i) Name substance Q.
(ii)When the bleaching powder is added to water during washing, a lot of soap is used. Explain
ANSWERS
(a) (i) Sodium chloride / potassium chloride /rock salt.
(ii) Concentrated sulphuric (VI) acid (iii) Grey solid turns green
(i) I The gas reacts with silver nitrate to form insoluble silver chloride
II Both gases form ammonium chloride which is white. (ii) To make hydrochloric acid. Manufacture of ammonium chloride. Manufacture of PVC. Making chloroethene /vinyl chloride
A gas jar full of chlorine water was inverted over water and allowed to stand for sometime
a)State and explain two observations made in the gas jar after some time.
b) Write the equation for the reaction between chlorine and hot concentrated potassium hydroxide
a)What is meant by the term radical?
b) The table below contains atoms that form common radicals. Complete the table to show radicals formed from various atoms.
A student used the set up below to prepare a sample of nitrogen gas.
a) State the function of potassium hydroxide in the set up
b) Give a suitable metal M for use in the combustion tube c) Give a reason why the nitrogen gas obtained is not pure.
ANSWERS
(a) It absorbs carbon (IV) oxide present in the air.
(b) Copper /Cu(S) (c) It has rare noble gases which have not been removed / Argon.
a) Name a suitable solvent for extracting an indicator form flowers:
b) Give a reason why the solvent named in (a) above is used
ANSWERS
(a) Acetone / ethanol / propanone / propanol.
(b) The solvent dissolves the organic compound indicator present in the flowers / it is an organic solvent.
Cotton is a natural polymer. State one advantage and one disadvantage of this polymer.
ANSWER
An organic compound had the following composition 37.21% carbon, 7.75% hydrogen and the rest chlorine. Determine the molecular formula of the compound, given that
the molecular mass of the compound is 65. (C=12.0; H=1.0; CL=35.5)
(a) A student electrolyzed dilute sodium chloride solution using inert carbon electrodes. Name the products at:
i)Anode : ii)Cathode: (b) If the experiment was repeated using concentrated sodium chloride instead of dilute sodium chloride solution, write the half equation at the anode.
Study the flow chart below and answer the question the follow.
a) Name the process in step I.
b) Identify the reagent in step II. c) Give one use of ethane
ANSWERS
(a) Step 1 is neutralisation.
(b) Step II is soda lime/ mixture of NaOH and CaO. (e) Fuel/making ethene/making hydrogen gas.
The set up below was used to separate a mixture of methanol and propanol. Study it and answer the question that follow.
a) State the function of X
b) Which liquid will collect first in the beaker? give a reason.
ANSWERS
Given that the atomic number of Y is 13 and that of Z is 9:
a)Write the electronic arrangement of Y and Z; b) Draw the dot (.) and cross(x) diagram for the compound formed by Y and Z
In the contact process, during the production of sulphur (VI) oxide, a catalyst is used.
Give two reasons why vanadium (V) oxide is preferred to platinum.
ANSWERS
Draw a set up that can be used to separate a mixture of sand and iodine
Use the part of the periodic table given below to answer the questions that follow (Letters are not the actual symbols of the elements)
a) Identify the element that forms giant covalent structures
b) Identify one element that does not form compounds c) Write the formula for the nitride of M
In an experiment on rates of reaction, potassium carbonate was reacted with dilute sulphuric (Vi) acid
(a)What would be the effect of an increase in the concentration of the acid on the rate of the reaction? (b) Explain why the rate of reaction is found to increase with temperature.
ANSWERS
(a) Rate increases.
(b) Temperature increases the kinetic energy of the particles increasing the number of collisions.
A measuring cylinder fitted with moist steel wool was inverted in a trough of water as shown in the diagram below
(a)State and explain the observations made on the;
i) Moist steel wool after four days. ii) Water level in the measuring cylinder after four days. (b) What would be the effect of using steel wool moistened with salty water?
ANSWERS
(a) (i) It turned brown /blue/violet/green.
(ii) The water level rose up the gas jar/occupy space left by reacted 02 (b) The brown colour would be more since the salt accelerates rusting/rust faster.
Study the set up below and answer the questions that follow
(a)Write an equation for the reaction between ammonia and copper (II) oxide.
(b) During the experiment, the colour of the contents in the water trough changed. State the colour change observed and give an explanation.
When 20cm3 of 1 M sodium hydroxide was mixed with 20cm3 of 1 M hydrochloric acid, the temperature rose by 6.70C Assuming the density of the solution is 1 g/cm3 and the specific heat capacity of the solution is 4.2Jg-1k-1.
(a) Calculate the molar heat of neutralization; (b) When the experiment was repeated with 1 M ethanoic acid, the temperature changes was found to be lower than that with 1 M hydrochloric acid. Explain.
100cm3 of 0.005 M sulphuric (VI) acid were placed in a flask and a small quantity of anhydrous sodium carbonate added. The mixture was boiled to expel all the carbon (IV) oxide. 25cm3 of the resulting solution required 18cm3 of 0.1 M sodium hydroxide solution to neutralize it.
Calculate the mass of sodium carbonate added. (Na = 23.0; O=16.0; C=12.0) |
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