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# (videnskab) Nogen der kan hjælpe?

12. februar 2021 af hawr0086

I. Write, if possible, the overall equation of the corresponding reaction when: a) we dip a strip of chrome in a thallium nitrate solution. b) we dip a thallium wire in a cadmium (II) nitrate solution. c) we dip a strip of chrome in a cadmium (I) nitrate solution.

Given: E "ntm = -0.34 V E'c3 + = - 0.74 V E'ca2 + ica = -0.40 V

II. a) Consider the cell: O Mg Mgt The emf of the cell, under standard coriditions, is E = 2.71 V. What is the standard potential of the couple Mg "/ Mg, if that of the couple Cu" / Cu is: E 'cu2 + ic = 0,34 V. b) Calculate the emf of the cell constructed from the couples Mg "/ Mg and Fe" / Fe knowing that the standard potential E'Fe2 + F = -0.44 V. | Cu * Cu e

We construct a cell using the following method: • a strip of chrome was dipped in 100 mL of a chromium (III) nitrate solution of concentration 0.1 mol.L ". A strip of silver was dipped in 100 mL of a silver nitrate solution of concentration 0.3 mol.L ". Connecting wires and a salt bridge were connecting the 2 compartments of the cell. a) Given E "c3 + ic = -0.74 V and E'agtiag = 0.80 V, indicate the direction of the electrons flow. Write the balanced cquation of the overall cell reaction. b) Calculate the change in the mass of Ag strip when the reaction ceases.

(Ag-108). c) Calculate the concentration of chromium (III) ions when the reaction ceases.% 3D IV. We connect the Au "/ Au half-cell, made of a gold strip dipped in a 1.0 x10 mol.L "solution of gold (III) chloride, to a hydrogen half-cell. The platinum electrode is the negative terminal of this cell which emf is: E = 1.44 V. 1) Sketch this cell and label it, then write the conventional cell notation. 2) Write the half-reactions occurring at the electrodes. Deduce the overall cell reaction. 3) What is the value of the potential of Au "/ Au couple? 4) The standard potential of Au "/ Au is 1.50 V. Justify the obtained result.

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