b Below are the standard electrode potentials for electrodes B and D B 2t aq 2e

B below are the standard electrode potentials for

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(b) Below are the standard electrode potentials for electrodes B and D B 2t (aq) + 2e - B (s) – 2.92V D 2t (aq) + 2e - D (s) + 0.34V (i) Identify the electrode which is ; (a) The least reducing agent (b) The strongest oxidizing agent (ii) Calculate the e.m.f of the cell formed when the two electrodes are connected (iii) Write a cell representative for the cell above 27.A typical electrolysis cell uses a current of 40,000 amperes. Calculate the mass (in Kg of aluminium produced in one hour). (Al = 27) (Faraday = 96500Coloumbs ) 28 . A strip of copper metal was immersed into a nitrate solution of metal Q overnight. Use the information below to answer questions that follow E (Volts) Q (aq) + e - Q (s) Cu 2+ (aq) + 2e - Cu (s) +0.80 + 0.34 (a) State the observations made at the end of the experiment (b) Give a reason for the observations made in (a) above(c) Calculate the e.m.f of the cell above 29. (a) Excess marble chips (Calcium carbonate) was put in a beaker containing 150cm 3 of dilute hydrochloric acid. The beaker was put on a weighing balance and the total loss in mass recorded after every two minutes as shown in the table below: (i) Why was there a loss in mass? (ii) The average rate of reaction was faster between 0 and 2 minutes than between 6 and 8 minutes. Explain why (iii) State one way in which the rate of reaction can be increased (iv) When aqueous sodium sulphate was added to contents of the beaker, a white precipitate was formed; (I) Identify the white precipitate ……………………………………………………… (II) Name one use of the substance named in ( iv) (I) above b) A student performed the following experiment with an intention to extract calcium metal (i) The student was surprised that no calcium was produced in the experiment. Explain why no calcium was produced (ii) Write the equation for the reaction that occurred at the anode if the solution was concentrated (iii) The electrolysis involved passing an electric current of 4A for one hour. Calculate the mass of the product at the anode. (1Faraday = 96500C, Cl =35.5, H = 1.0, O =16, Ca = 40) 30. Cheptoo set-up some apparatus as shown in the diagram below:- Time (min) 0 2 4 6 8 10 Total loss in mass (g) 0 1.8 2.45 2.95 3.2 3.3
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At the start of the experiment, the bulb did not light:- (a) State and explain the observation made when the tap was opened to allow the hydrogen chloride gas through the water for about 20 minutes (b) Write the chemical equation for the reaction that took place at the cathode 31. Metals K and N were connected to form a cell as shown in the diagram below. Their reduction potentials are as shown below: K + (aq) / K (s) - 0.17V N + (aq) / N (s) = + 1.1 6V I. Write the equation for the half-cell reaction that occurs at Metal K electrode Metal N electrode II Identify P and state its role in the above setup (i). Identity of P (ii) . Role of P in the setup. III. On the diagram, show the flow of I. Electrons II. Current.
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