KCSE CHEMISTRY QUESTIONS AND ANSWERS PER TOPIC
0.63g of lead powder were dissolved in excess nitric acid to form lead nitrate solution. All the lead nitrate solution was reacted with sodium sulphate solution.
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a) Distinguish between isotopes and allotropes.
b) The chart below is part of the periodic table. Study it and answer the questions that follow.(The letters are not the actual symbols of the elements).
i) Select the element in period three which has the shortest atomic radius. Give a reason for you answer.
ii) Element F has the electronic structure, 2.8.18.4 on the chart above, indicate the position of element F. iii) State one use of the elements of which E is a member. iv) Write an equation to show the action of heat on the nitrate of element C. c) When 3 litres of chlorine gas were completely reacted with element D, 11.875g of the product were formed. Determine the relative atomic mass of element D. (Atomic mass of chlorine = 35.5; molar gas volume = 24litres) The empirical formula of a hydrocarbon is C2H3.The hydrocarbon has a relative molecular mass of 54..(H = 1.0, C = 12.0). a) C2H3 b) Draw the structural formula of the hydrocarbon c) To which homologous series does the hydrocarbon drawn in (b) above belong?
When 94.5g of hydrated barium hydroxide, ba(OH)2. nH2O were heated to constant mass, 51.3g of anhydrous barium hydroxide were obtained. Determine the empirical formula of the hydrated barium hydroxide.
(a) In an experiment, dry hydrogen chloride gas was passed through heated zinc turnings as shown in the diagram below. The gas produced was then passed through heated lead (II) oxide.
Calculate the mass of nitrogen dioxide gas that would occupy the same volume as 10g of hydrogen gas at same temperature and pressure.(H = 1.0, N = 14.0, o = 16.0)
When a hydrocarbon was completely burnt in oxygen, 4.2g of carbon dioxide and 1.71 g of water were formed. Determine the empirical formula of the hydrocarbon
(H= 1.0 ; C=12.0 ; 0 = 16.0)
A certain carbonate, GCO3, reacts with dilute hydrochloric acid according to the equation given below:
GCO3(s) + 2HCL(aq)= GCl2 (aq) + (CO2(g) + H2O(l) If 1 g of the carbonate reacts completely with 20 cm3 of 1 M hydrochloric acid ,calculate the relative atomic mass of G (C = 12.0 = 16.0)
When X cm3 of a solution of 0.5m magnesium carbonate was 8.4g.
a) Write the ionic equation for the reaction that took place b) Calculate the value of X. (C = 12.0, Mg 24.0; 016.0 In an experiment, 2.4g of sulphur was obtained by reacting hydrogen sulphide and chorine as shown by the equation below: H2S(g) + Cl2(g) → S(s) + 2HCl(g) (a) Which of the reactants acts as a reducing agent in the above reaction? Explain. (1 mk) (b) Given that the yield of sulphur in the above reaction is 75%, calculate the number Of moles of H2S(g) used in the reaction (S=32.0)
The set – up below was used to prepare hydrogen gas
a) Complete the diagram to show how a dry sample of hydrogen gas can be collected
b) Write an equation for the reaction, which takes place when hydrogen gas burns in air. c) i)1.2 litres of hydrogen gas produced at room temperature and pressure when 3.27g of zinc was used. Determine the relative atomic mass of zinc.(Molar gas volume is 24 litres) d) State two industrial uses of hydrogen gas.
When excess dilute hydrochloric acid was added to sodium , 960cm3 of sulphur (IV) oxide gas was produced. Calculate the mass of sodium sulphite that was used. (molar mass of sodium = 126 g and molar gas volume= 24000cm3
In an experiment 30cm3 of 0.1 M sulphuric acid were reacted with 30cm3 of 0.1 M sodium hydroxide
(a) Write in equation of the reaction that took place (b) State the observations that were made when both and red litmus papers were dropped into the mixture (c) Give a reason for your answer in (a) above Zinc metal and hydrochloric acid reacts according to the following equation Zn(s) + 2HCI (aq)→ ZnCI2 (aq) + H2 (g) 1.96 g of zinc were reacted with 100cm3of 0.2M hydrochloric acid (a) Determine the reagent that was in excess (b) Calculate the total volume of hydrogen gas was liberated S.T.P (Zn= 65.4 Molar gas volume = 22.4 litres at S.T.P) A compound has an empirical formula, C3H6O and a relative formula mass of 16. Determine its molecular formula (H + 1.0, C = 12.0, O = 165.0) (2mk) |
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