KNEC Chemistry Paper 1 Question Paper / 2016 KCSE MOKASA Joint Examination

Explain the following:
(i) It is always advisable to scoop chemical substances using a clean spatula.
( ½ mark)
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(ii) Flammable substances should always be kept away from flames in the laboratory.
( ½ mark)
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Name one reagent that can be used to distinguish between Al³⁺ and Zn²⁺ ions in solution
and state what would be observed if each of the ions is treated with the reagent you have
named.
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Manganese sulphide reacts with acids according to the following equation.

State, giving a reason what would happen to the equilibrium if;
(i) Water is added to the equilibrium mixture. (1 ½ marks)
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(ii) Hydrogen chloride is bubbled into the equilibrium mixture. (1 ½ marks)
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Use the thermochemical equations below to answer the questions that follow.

(i) Draw an energy cycle diagram to show the enthalpy of formation of ethane.
(1 ½ marks)

(ii) Calculate the enthalpy of formation of ethane. (1 ½ marks)

State the conditions under which copper reacts with sulphuric acid and give an equation
for the reaction.
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When 8.8g of hydrocarbon Z was burnt in excess air, 14.4g of water and 11.95 dm³ of
carbon (IV) oxide were obtained at s.t.p. Determine the empirical formula of Z.

Perspex is a synthetic polymer of formula

(a) Write the structural formula of the monomer of Perspex. (1 mark)
(b) State the type of polymerization involved in the formation of perspex.
(1 mark)
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When zinc granules are dropped into two separate solutions of dilute sulphuric (VI) and
concentrated sulphuric (VI) acid, effervescence of a colourless gas occurs in each case.
Give equations to represent the reactions that take place.
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Study the chart below and answer the questions that follow.

(a) Identity solid X. (1 mark)
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(b) Write an ionic equation for the reaction between P and copper (II) sulphide
solution. (1 mark)
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(c) State the observation made when gas P is bubbled through iron (III) chloride
solution. (1 mark)
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Use the nuclear equations below to answer the questions that follow.

(i)
(ii)

(a) Give the actual names of particles X and Y. (1 mark)
X ………………………………………………………………………………………………
Y ………………………………………………………………………………………………
(b) Give the name of a radiation whose emission does not change the mass number
or the atomic number of a radioisotope. (1 mark)
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The structures below represent two cleaning agents M and P.

Which cleaning agent would be most suitable for use with water containing calcium
sulphate. Give a reason.
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You are given the following half equations:

(i) Obtain an equation of the cell reaction. (1 mark)
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(ii) Calculate the  value for the cell. (1 mark)
(iii) Give the oxidizing species. (1 mark)
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Using dots (●) and crosses (×) to represent outermost electrons; draw diagrams to show
bonding in:

(a) Aluminium chloride. (1 ½ marks)
(b) Sulphuric (IV) oxide. (1 ½ marks)

Use the information in the table below to answer the questions that follow.

(a) Write the electron arrangement of: (1 mark)
(i) ion of S ……………………………………………….
(ii) atom of T ……………………………………………….

(b) Explain why the melting point of T is higher than that of U. (2 marks)
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Complete the table below.

The diagram below represents a set up used for the large scale manufacture of hydrochloric acid.

(a) Name substance X. (1 mark)
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(b) What is the purpose of the glass beads? (1 mark)
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(c) Give one use of hydrochloric acid. (1 mark)
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Calculate the volume of nitrogen (I) oxide produced when 38.2g of ammonium nitrate is
completely decomposed by heating (at s.t.p). (N = 14, H = 1, O = 16)

Give equations to show the reactions that take place when;
(a) iron reacts with steam. (1 mark)
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(b) Give one industrial use of the gas produced in the reactions in (i) and (ii) above.
(1 mark)
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(a) When magnesium metal is burnt in air, it reacts with both oxygen and nitrogen
gases giving a white ash. Write two equations for the reactions that take place.
(2 marks)
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(b) Give the total number of atoms present in the gas produced when water is added
to magnesium nitrate. (1 mark)
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The graph below shows the behavior of a fixed mass of a gas at constant temperature.

(a) What is the relationship between the volume and the pressure of the gas?
(1 mark)
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(b) 60 cm³ of oxygen gas diffused through a porous partition in 50 seconds. How
long would it take 60cm³ of sulphur (IV) oxide gas to diffuse through the same
partition under the same conditions? (S = 32.), O = 16.0)
(3 marks)

State and explain the observation made when a moist red litmus paper is put in a gas jar
of dry chlorine gas.
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(a) When extinguishing a fire caused by burning kerosene, charbon (IV) oxide is
preferred to water. Explain. (2 marks)
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(b) Write the formula of the oxide of carbon which is ‘silent killer’. (1 mark)
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Explain why chlorine is a gas while iodine is a solid at room temperature.
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Apart from their location, state any two differences between a proton and an electron.
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What term is given to: The amount of energy given out when a neutral atom in gaseous
state gains an electron?
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A certain fertilizer is suspected to be containing nitrate ions. Describe how the presence
of nitrate ions can be determined in such fertilizer.
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Write balanced chemical equations to show the action of heat on the following nitrates.
(a) Lead (II) nitrate (1 mark)
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(b) Silver nitrate (1 mark)
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Starting with zinc carbonate solid describe how zinc hydroxide can be prepared in the
laboratory.
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Below is a scheme of some reactions starting with but-z-yne. Study it and answer the
questions that follow.

(a) Name Y, X and T (1 ½ marks)
Y ……………………………………………………………………………….
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T ……………………………………………………………………………….
(b) Give the name of the following organic compounds. ( ½ mark)

The following results were obtained during an experiment to determine the solubility of
potassium nitrate in water at 300C. Mass of dish = 15.86g, mass of dish + saturated
solution at 30^oC = 26.86g, mass of dish + solid KNO₃ after evaporation to dryness = 16.7g. Calculate the mass of saturated solution containing 60.0g of water at 30^oC.