1 Form Three student prepared an experiment to prepare a gas in the laboratory by decomposing a compound using electricity . A steady current was allowed to flow through the solution for 3 hours. At s.t.p 4.12dm^3 of the gas which relighted the glowing splint was produced. (a) What terminology is used to refer to such experimental set up? (b) Work out the current flowing in the circuit. 7. Classify the following salts on the basis of solubility in water.Sodium carbonate, Lead nitrate, Silver chloride, Copper (II) sulphate, Barium sulphate Zinc chloride and Lead sulphate. Table 2 shows the volume of soap solution needed to form lather with three samples of water of equal volumes. Use the data from the table to answer the questions that follow: Table 2 Water Sample Volume of Soap Solution (cm^3) E 6.5 F 0.2 G 3.7 (a) Identify two things other than the volume of water that must be kept constant for such data to be meaningful. (i) Identify which water sample has the highest hardness Give a reason. (ii) Give three causes of hardness of water. - I Consider the following substances: milk, copper,soap, steel, chlorine and sugar. (a) Identify the elements , compounds and mixtures from the list. (b) Give four differences between the elements identified in 9(a).

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1 Form Three student prepared an experiment to prepare a gas in the laboratory by decomposing a compound using electricity . A steady current was allowed to flow through the solution for 3 hours. At s.t.p 4.12dm^3 of the gas which relighted the glowing splint was produced. (a) What terminology is used to refer to such experimental set up? (b) Work out the current flowing in the circuit. 7. Classify the following salts on the basis of solubility in water.Sodium carbonate, Lead nitrate, Silver chloride, Copper (II) sulphate, Barium sulphate Zinc chloride and Lead sulphate. Table 2 shows the volume of soap solution needed to form lather with three samples of water of equal volumes. Use the data from the table to answer the questions that follow: Table 2 Water Sample Volume of Soap Solution (cm^3) E 6.5 F 0.2 G 3.7 (a) Identify two things other than the volume of water that must be kept constant for such data to be meaningful. (i) Identify which water sample has the highest hardness Give a reason. (ii) Give three causes of hardness of water. - I Consider the following substances: milk, copper,soap, steel, chlorine and sugar. (a) Identify the elements , compounds and mixtures from the list. (b) Give four differences between the elements identified in 9(a).

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6. (a) The experimental setup described in the question, where a gas is produced by decomposing a compound using electricity, is commonly referred to as an electrolysis experiment.(b) To work out the current flowing in the circuit, you can use the formula:

Given that the charge is related to the amount of substance produced in an electrolysis reaction, you can calculate the current by dividing the total charge passed through the solution by the time taken.7. - Soluble salts: Sodium carbonate, Lead nitrate, Copper (II) sulphate, Zinc chloride- Insoluble salts: Silver chloride, Barium sulphate, Lead sulphate8. (a) Two things other than the volume of water that must be kept constant for such data to be meaningful are: - Concentration of soap solution - Temperature of water(b) (i) Water sample F has the highest hardness because it required the least volume of soap solution to form lather, indicating the presence of more dissolved minerals causing hardness.(ii) Three causes of hardness of water are: - Presence of calcium and magnesium ions - Dissolved bicarbonates - Dissolved sulfates9. (a) - Elements: Copper, Chlorine- Compounds: Milk (contains various compounds), Soap (typically contains sodium or potassium salts of fatty acids)- Mixtures: Steel (alloy of iron and carbon), Sugar (pure substance but can be mixed with other substances)(b) Four differences between the elements identified in 9(a) could include:- Physical properties (e.g., color, density)- Chemical reactivity- Atomic structure (number of protons, neutrons, electrons)- Occurrence in nature

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