KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
When aluminium oxide was electrolysed, 1800kg of aluminium metal were obtained.
a) Write equation for the formation of aluminium metal b) Calculate the quantity of electricity in faradays used (Al=27)
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An isotope of element E has 34 neutrons and its mass number is 64. E forms a cation with 28 electrons. Write the formula of the cation with 28 electrons. Write the formula of the cation indicating the mass and atomic numbers.
In terms of structure and bonding, explain why the melting point of oxygen is much lower than that of sodium.
ANSWER
ANSWERS
(a) Water
(b) The second / other product of burning candle is carbon (IV) oxide (l). It can be prevented from getting into the environment by passing it though a hydroxide solution/ alkaline solution e.g. K.O.H NaOH or aqueous ammonia . To form K2CO3
ANSWERS
(i) 2.8.8 (ii) 2.8.2
Hardness of water may be removed by either boiling or addition of chemicals
a) write an equation to show how boiling removes hardness of water. b) name two chemicals that are used to remove hardness of water.
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,)
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The scheme below shows some reaction sequence starting with solid N.
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The formula given below represents a portion of a polymer Give:
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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
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Describe how a solid sample of lead (II) Chloride can be prepared using the following reagents, dilute nitric acid, dilute hydrochloric acid and lead carbonate.
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ANSWERS
(a) Energy required to remove 1 mole of electrons from 1 mole of gaseous atoms
(b) B 418??? It loses electrons most readily Reject lowest i.e. Mg (HCO3) 2 aq →MgCS O3 + H2O + CO2 (g) 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
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The grid below shows part of a periodic table. The letters do not represent the actual symbols of the elements
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Draw the structural formula of:
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ANSWERS
(a) Neutralization
(b)(i)Calcium hydrogen carbonate (ii)Drying agent Extraction of sodium metal
Crude oil contains sulphur. What would be the effect to the environment of using fuel containing sulphur?
ANSWERS
A certain mass of a metal E1 reacted with excess dilute hydrochloric acid at 25°C. The volume of hydrogen gas liberated was measured after every 30 seconds. The results were presented as shown in the graph below.
a) Name one piece of apparatus that may have been used to measure the volume of gas liberated. b) (i) On the same axis, sketch the curve that would be obtained if the experiment was repeated at 35°C. (ii) Explain the shape of your curve in b(i) above.
ANSWERS
(a)(i)Cryolite
(ii)Electrolysis (b)Good conductor Does not rust Malleable Light High M.P Does not corrode easily
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
When solid B1 was heated, a gas which formed a white precipitate when passed through lime water was produced. The residue was dissolved in dilute nitric (V) acid to form a colourless solution B2. when dilute hydrochloric acid was added to solution B2 a white precipitate which dissolved on warning was formed.
a) Write the formula of the; I Cation in solid B1 II anion in solid B1 b) Write an ionic equation for the reaction between the resdue and dilute nitric (V) acid.
Distinguished between a strong and a weak acid. Give examples.
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