The following diagram represents the modern periodic table with representative elements lettered A, B and C. Use the electronic configuration of each element to identify their blocks.

1. State one characteristic of elements in the block of element B. (1 mk)

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Use the Hess’s law to calculate the standard enthalpy of the reaction A + B -----------→C given the following standard enthalpy values: ΔHθf (A) = +411 kJ mol-1 ΔHθf (B) = -252 kJ mol-1 ΔHθf (C) = +525 kJ mol-1

1. Calculate the standard enthalpy of the reaction A + B ----------→ C. (3 mk)

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(a) Student A carried ten moles of water in a liquid form while student B carried the same number of moles of water in vapour form. Who carried heavier weight than the other? Briefly, explain. (b) How many moles of nitrogen gas are there in 3.5 x 10^20 molecules of the gas?

1. Student A carried ten moles of water in a liquid form while student B carried the same number of moles of water in vapour form. Who carried heavier weight than the other? Briefly, explain. (2 mk)
2. How many moles of nitrogen gas are there in 3.5 x 10^20 molecules of the gas? (2 mk)

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Triamminetriaquachromium(III) chloride is among of the complex compounds. Briefly explain two conditions which favour formation of such compound.

1. Explain another condition that favors the formation of Triamminetriaquachromium(III) chloride. (2 mk)

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Briefly, justify the following observations: (a) 4-nitrophenol (p-nitrophenol) is more acidic than 4-nitromethylphenol (p-methylphenol). (b) Reactions of phenylamine favours more electrophilic substitution at para and ortho positions than at meta position.

1. 4-nitrophenol (p-nitrophenol) is more acidic than 4-nitromethylphenol (p-methylphenol). Briefly, justify. (2 mk)
2. Reactions of phenylamine favours more electrophilic substitution at para and ortho positions than at meta position. Briefly, justify. (2 mk)

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Suppose you carried out an experiment to determine pH of soil in a school farm and you found the pH of 9.5; How would you correct it to a pH below 7.0? Give four ways.

1. Suggest a fourth way to correct the soil pH from 9.5 to below 7.0. (1 mk)

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The teaching and learning of Chemistry subject is guided by several principles. What considerations do these principles emphasize with regards to the student learning? Give four points.

1. State a fourth consideration emphasized by chemistry teaching principles for student learning. (1 mk)

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You are invited at Mwangaza secondary school to prepare a practical work about titration between HCl and NaHCO3. Suggest the standard volumetric apparatus and indicator that could be used during titration.

1. Suggest a suitable indicator for the titration of HCl and NaHCO3. (1 mk)

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You have been invited to a certain school where staffs have contradiction between a syllabus and the curriculum. How would you help them to differentiate the two concepts? Give four points.

1. Explain a fourth way to differentiate between a syllabus and a curriculum. (1 mk)

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When Fe3+ and Sn2+ are simultaneously introduced into aqueous solution, the reaction begins immediately. The ionic equation representing the reaction is: 2Fe+3 (aq) + Sn2+ (aq)------→ 2Fe2+ (aq) + Sn4+ (aq)

1. Write the half-equation for the reduction process. (1 mk)

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