KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
When a hydrated sample of calcium sulphate CaSO4 .XH2O was heated until all the water was lost, the following data recorded;
Mass of crucible = 30.296 g Mass of crucible +hydrated salt = 33.111 g Mass of crucible + anhydrous salt = 32.781 g Determine the empirical formula of the hydrated salt (Relative formula mass of CaSO4 =136, H2O =18).
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(a) The diagram below represents a set up that was used to obtain dry nitrogen from air. Study it and answer the questions that follow
Related Chemistry Questions and Answers on ​nitrogen and its compounds form 3 level
A small crystal of potassium manganate (VII) was placed in a beaker water. The beaker was left standing for two days without shaking. State and explain the observations that were made.
ANSWERS
The diagram below shows the set up used in an experiment to prepare chlorine gas and react it with aluminium foil. Study it and answer the question that follow
(a) In the experiment, concentrated hydrochloric acid and potassium manganate (VII) were used to prepare chlorine gas. State two precautions that should be taken in carrying out this experiment.
(b) Write the formula of another compound that could be used instead of potassium manganate (VII) (c) Explain why it is necessary to allow the acid to drip slowly onto potassium manganate (VII) before the aluminium foil is heated. (d) State the property of the product formed in the combustion tube that makes it possible for it to be collected in the receiver (e) When 1.08g of aluminum foil were heated in a stream of chlorine gas, the mass of the product formed was 3.47 g Calculate the: (i) Maximum mass of the product formed if chlorine was in excess; (Al= 27; Cl = 35.5) (ii) Percentage yield of the product formed (f) Phosphorous trichloride is a liquid at room temperature. What modification should be made to set up if it is to be used to prepare phosphorous trichloride?
(a) Give the names of the following compounds
(b) Study the information in the table below and answer the questions that follow
(i) Name the reagents used in:
Step I ……………………. Step II …………………….. Step III …………………….. (ii) Write an equation for the complete combustion of CH = CH (iii) Explain one disadvantage of the continued use of items made from the compound formed in step III
ANSWER
State and explain the observations made when excess ammonia gas reacts with chlorine gas
ANSWERS
ANSWERS
6.84g of aluminium sulphate were dissolve in 150cm3 of water. Calculate the molar concentration of the sulphate ions in the solution. (Relative formula mass of aluminium sulphate is 342)
The relative formula mass of a hydrocarbon is 58. Draw and name two possible structures of the hydrocarbon (C=12.0; H=1.0)
a) State the Charles law
b) The volume of a sample of nitrogen gas at a temperature of 291 K and 1.0x105 Pascal‟s was 3.5 x 10-2m3. Calculate the temperature at which the volume of the gas would be 2.8 x 10-2m3 at 1.0 x 105 Pascal.
In an experiment, a few drops of concentrated nitric acid were added to aqueous iron(II) sulphate in a test – tube. Excess sodium hydroxide solution was then added to the mixture.
a) State the observations that were made when: i) Concentrated nitric acid was added to aqueous iron (II) sulphate ii) Excess sodium hydroxide was added to the mixture. b) Write and ionic equation for the reaction which occurred in (a) (ii) above
15.0cm3 of ethanoic acid (CH3COOH) was dissolved in water to make 500cm3 of solution. Calculate the concentration of the solution in moles per litre. (C=12.0;H=1.0;O=16.0; density of ethanoic acid is 1.05 g/cm3)
90cm3 of 0.01M calcium hydroxide were added to a sample of water containing 0.001 moles of calcium hydrogen carbonate. a) Write an equation for the reaction which took place b) Calculate the number of moles of calcium ions in 90cm3 of 0.01M calcium hydroxide. c) What would be observed if soap solution was added drop wise to a sample of the water after the addition of calcium hydroxide? Give a reason. A gas occupies a volume of 400cm3 at 500k and 1 atmosphere pressure. What will be the temperature of the gas when the volume and pressure of the gas is 100cm3 and 0.5 atmospheres respectively.
In an experiment, chlorine gas was passed into moist hydrogen sulphide contained in a boiling tube as shown in the diagram
a) What observation was made in the boiling tube?
b) Write an equation for the above reaction. c) What precaution should be taken in carrying out this experiment? Give a reason.
0.63g of lead powder were dissolved in excess nitric acid to form lead nitrate solution. All the lead nitrate solution was reacted with sodium sulphate solution.
a) The diagram below shows some processes that take place during the industrial manufacture of sulphuric acid.
(i) Write the equation for the reaction in which sulphur dioxide gas is produced.
(ii) Why is it necessary to keep the gases pure and dry ? (iii) Describe the process that takes place in chamber G. (iv) Name the gases that escape into the environment. (v) State and explain the harmful effect on the environment of one of the gases named in (iv) above (vi) Give one reason why it is necessary to use a pressure of 2-3 atmospheres and not more. b) (i) Complete the table below to show the observations made when concentrated sulphuric acid is added to the substances shown.
(ii) Give reasons for the observations made using:
I iron fillings II Crystals of white sugar. (c) Name one fertilizer made from sulphuric acid. (d) Suggest a reason why BaSO4(a pigment made from sulphuric acid) would be suitable in making paint for cars.
a) Distinguish between isotopes and allotropes.
b) The chart below is part of the periodic table. Study it and answer the questions that follow.(The letters are not the actual symbols of the elements).
i) Select the element in period three which has the shortest atomic radius. Give a reason for you answer.
ii) Element F has the electronic structure, 2.8.18.4 on the chart above, indicate the position of element F. iii) State one use of the elements of which E is a member. iv) Write an equation to show the action of heat on the nitrate of element C. c) When 3 litres of chlorine gas were completely reacted with element D, 11.875g of the product were formed. Determine the relative atomic mass of element D. (Atomic mass of chlorine = 35.5; molar gas volume = 24litres) The empirical formula of a hydrocarbon is C2H3.The hydrocarbon has a relative molecular mass of 54..(H = 1.0, C = 12.0). a) C2H3 b) Draw the structural formula of the hydrocarbon c) To which homologous series does the hydrocarbon drawn in (b) above belong?
ANSWERS
a)Conc. H2SO4
b)Heat the solution to concentrate it. Allow for crystal for form. Filter. c)Anhydrous copper(II) Sulphate
The first step in the industrial manufacture of nitric acid is the catalytic oxidation of ammonia gas.
(a) What is the name of the catalyst used? (b) Write the equation for the catalytic oxidation of ammonia gas. (c) Nitric acid is used to make ammonium nitrate, state two uses of ammonium nitrate.
When hydrogen sulphide gas was bubbled into an aqueous solution of iron (III) chloride, a yellow precipitate was deposited.
a) The standard reduction potential for Fe2+ (aq) is -0.44 volts. Select the element which would best protect iron from rusting. b) Write an equation for the reaction that took place. c) What type of reaction was undergone by hydrogen by hydrogen sulphide in this reaction?
The diagram below represents the set-up that was used to prepare and collect hydrogen chloride gas in the laboratory.
a) State the purpose of concentrated sulphuric acid in the wash bottle.
b) Write an equation for the reaction between dry hydrogen chloride gas and heated iron c) Hydrogen chloride gas is dissolved in water to make hydrochloric acid. State one use of hydrochloric acid.
Name the process which takes place when:
a) Solid carbon (IV) oxide (dry ice) changes directly into gas b) A red litmus paper turns white when dropped into chlorine water. c) Propane gas molecules are converted into a giant molecule
ANSWERS
a)sublimation
b)Bleaching. c)Polymerization |
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