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These are chemistry questions and answers categorized according to topics, papers i.e. Paper 1 and 2, Levels i.e. form 1 to form 4, kcse year the examination was done and section A or B
Select topic/category to open topical questions from that particular option provided. Chemistry Topics
(NH4)2HPO4 is a fertilizer used by farmers to boost their crop production.
(a) Calculate the mass of phosphorus in a 20 kg packet 14.0; H = 1.0; P = 31.0; 0 16.0) (b) State one advantage of this fertilizer, (NH4)2HPO4 over urea CO(NH2)2
ANSWERS
Study the flow chart in Figure 1 and answer the questions that follow.
Gas N forms a while suspension with aqueous calcium hydroxide.
(a) Name the anion present in the potassium salt. (b) Write an ionic equation for the formation of solid M. (c) Give one use of gas N.
ANSWERS
The set-up in Figure 4 can be used to prepare nitrogen (II) oxide. Use it to answer the questions that follow.
(a) Name substance A
(b) When the gas jar containing nitrogen (II) oxide is exposed to air, a brown color is observed. Explain. (c) Write an equation for the reaction which occurred in the flask.
ANSWERS
In an experiment, concentrated nitric(V) acid was reacted with iron(II) sulphate. State and explain the observations made.
ANSWERS
The mixture changed from green to yellow / formation of a brown gas;
Iron(II) ions is oxidized by nitric(V) acid to Iron(III) ions / nitric(V) acid is reduced to nitrogen(1I) oxide which is oxidized by oxygen to nitrogen(IV ) oxide.
Copper(II) ions react with excess aqueous ammonia to form a complex ion.
(a) (i) Write an equation for the reaction that forms the complex ion. (ii) Name the complex ion. (b) Explain why CH4 is not acidic while HCl is acidic yet both compounds contain hydrogen.
ANSWERS
(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 E, F 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.
ANSWERS
Figure 3 is a flow chart that shows the process that occurs in the manufacture of nitric (V) acid.
(a) Name substance P, Q, R and S.
To obtain substance R, ammonia is heated at 9000C in the presence of air and a catalyst.
The product is then cooled in air.
(e) When ammonia ¡s reacted with nitric(V) acid, it produces a nitrogenous fertiliser.
Expected Response
When fuels burn in the internal combustion engine at high temperature, one of the products formed is nitrogen (II) oxide.
(a) Write the equation for the formation of nitrogen (II) oxide. (b) Give a reason why nitrogen (II) oxide is not formed at room temperature. (c) Describe how formation of nitrogen (II) oxide in the internal combustion engine leads to gaseous pollution.
ANSWERS
(a)N2(g) + 02(g) 2NO(g)
(b)Nitrogen atoms in the molecule are joined by strong triple covalent bond that requires a lot of energy to break than provided at room temperature (c) Nitrogen (II) oxide reacts with oxygen in air to form nitrogen (IV) oxide that dissolves in water vapour causing acid rain.
Ammonium ion has the following structure
Label on the structure:
(a) covalent bond; (b) coordinate (dative) bond.
ANSWERS
When burning magnesium ribbon is introduced into a gas jar full of nitrogen, it continues to burn producing a greenish yellow powder.
Expected Response
Dry ammonia and dry oxygen were reacted as shown in the diagram below
a)What is the purpose of the glass wool?
b) What products would be formed if red hot platinum was introduced into a mixture of ammonia and oxygen?
ANSWERS
(a)The purpose of the glass wool. It spreads the oxygen evenly/increase surface area or enriches the air with oxygen.
(b)Forms NO, Nitrogen (II) Oxide and steam
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.
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.
ANSWERS
Dry ammonia gas was passed over heated lead (II) oxide and the product passed over anhydrous Copper (II) sulphate as shown in the diagram below.
State:
(a)Two observations made in the combustion tube. (b) The property of ammonia gas shown in this experiment
ANSWERS
(a)The anhydrous copper (II) Sulphate turns from white to blue.
A grey solid is formed/droplets of a colourless liquid condense at cool part (b)Reducing property. |
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December 2024
AuthorMaurice Atika is a teacher and a netprenuer. |
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