CHEMISTRY 1 FORM FOUR PRE-KIPSSA EXAMINATION

SECTION B (54 MARKS)
Answer all questions in this section.
3. (a) Michael Faraday conducted many experiments on electrolysis and formulated laws of electrolysis . State the laws that Faraday formulated.
(b) A current of 4 Amperes is passed through dilute suphuric acid for 5 hours. Calculate the volume of hydrogen and oxygen at STP produced at the cathode and anode.
4. (a) Explain why:
(i) Burning a fuel containing sulphur as an impurity causes acid rain
(ii) The presence of too much sulphur dioxide in the atmosphere has a damaging effect on many buildings made of marble, a form of calcium carbonate.
(b) When sulphur dioxide gas is bubbled through the solution of acidified potassium permanganate, a chemical reaction occurs. The reaction progress can be evidenced by the colour change observed during the reaction. Use the provided information about the reaction to answer the following questions:
(i) Write a balanced molecular equation for the reaction.
(ii) Identify the type of chemical reaction involved.
(iii) Write an ionic equation for the reaction written in (i) above.
(iv) Describe the colour change during the reaction.
5. (a) Define the following terms:
(i) Mole
(ii) Avogadro’s constant
(iii) Molar mass
(b) Calculate the number of moles present in:
(i) 44 g of carbon dioxide (CO₂)
(ii) 36 g of water (H₂O)
(c) 5.6 dm³ of oxygen gas was measured at STP. Calculate:
(i) The number of moles of oxygen gas present.
(ii) The number of oxygen molecules in the sample.
(d) Magnesium reacts with hydrochloric acid according to the equation below: Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)
Calculate the volume of hydrogen gas produced at STP when 12 g of magnesium reacts completely with excess hydrochloric acid

6. (a) Naturally occurring silicon has three isotopes 28Si, 29Si, and 30Si. The most abundant isotope is 28Si which accounts for 92.23% of naturally occurring silicon. Given the observed atomic mass of silicon is 28.09, calculate the percentage of 29Si, and 30Si in nature.
(b) 12.915 g of a biochemical substance containing only carbon, hydrogen, and oxygen was burned in an atmosphere of excess oxygen. Subsequent analysis of the gaseous result yielded 18.942 g carbon dioxide and 7.749 g of water. Determine the empirical formula of the substance.
7. A group of Form Four students at Mtakuja Secondary School performed an experiment to study the rate of reaction between dilute hydrochloric acid (HCl) and marble chips (CaCO3). They measured the volume of gas produced over time.
(a) Write a balanced chemical equation for the reaction between calcium carbonate and hydrochloric acid, including state symbols.
(b) The students noticed that the reaction happened much faster when they used powdered marble instead of large chips.
(i) Explain why the reaction rate increased when using powder.
(ii) Based on the Collision theory, explain how increasing the temperature of the acid would affect the rate of this reaction.
(c) Apart from surface area and temperature, state three other factors that can alter the rate of a chemical reaction.
8. An unknown green sample was mixed with dilute HNO3 and gave a blue solution and a gas that precipitated limewater. The resulting solution was evaporated to dryness. Upon further heating, a black residue and brown gas were formed; a gas was also observed to relight a glowing splint.
(a) Identify the green sample, the blue solution, the black residue, and the two gases.
(b) Give the balanced chemical equation for the reactions.
(i) Green sample and nitric acid
(ii) The formation of black residue


SECTION C (30 MARKS)
Answer only two questions in this section.
9. The agricultural officer at Kibaha Town Council conducted a seminar to demonstrate the methods of applying fertilizers to crops for better yields. As a Form Four student, provide

clear explanations of the six methods of fertilizer application that the seminar will demonstrate.
10. Qualitative analysis is concerned with the investigations and identification of chemical species that make up a substance. It involves a set of analytical procedures that provide non-numerical data about analytes. By using six points, explain the applications of qualitative analysis in real life.

11. (a) (i) Define the term isomerism.
(ii) Draw and name all the possible isomers of the third member of alkene family. .
(b) Name the following organic compounds:
(i) CCl4

(ii)

(iii)

CH3CH2CHCH2CHCH = CHCH3
Br Cl
CH3CH2CHCH2OH CH3

(iv) CH3CH2CH2COOH
(c) Complete and balance the following reaction
(i) CH3CH = CH2(g) + Br2(g) →
(ii) CH3CH2COOH(aq) + CH3CH2OH(aq) →
(iii) CH3CH2CH2OH(aq) + Na(s) →
(iv) CH2 = CH2(g) + H2(g) →