AG°m=AHm-TASm =-2000Jmo-(25+273)K(+4JKmo) =-3,192Jmol =-3.19 kJ mol (b)Is this reaction spontaneous?If so,why do diamonds not appear to spontaneously change to graphite? The reaction is spontaneous,but it is so slow that it can not be observed. Part C.Answer any three of the six questions.If you answer more than three,the best three will be used to calculate your mark(20 marks each). 1. For a Galvanic cell using the half-reactions: VO2(+2Hg+e>VO*ag+H2Od) E°=1.00V Zn2am+2e→Zng E°=-0.76V (a)Determine the overall balanced cell reaction. 2 VO2'(+4H'(ag)+22 VO(ag)+2 H2O0 Zng→Zn2am+2e 2 VO2(ag)+4 H'(ag)+Zn(s)>2 VO(ag)+2 H2Od)+Zn(ag (We know the reaction is in this direction because it must be a Galvanic cell,i.e.it must have E) (b)Calculate the standard cell potential (V). E°el=1.00+0.76=1.76V 3 ΔGo rxn = ΔHo rxn - TΔSo rxn = -2000 J mol-1 – (25+273)K(+4 J K-1 mol-1) = -3,192 J mol-1 = -3.19 kJ mol-1 (b) Is this reaction spontaneous? If so, why do diamonds not appear to spontaneously change to graphite? The reaction is spontaneous, but it is so slow that it can not be observed. Part C. Answer any three of the six questions. If you answer more than three, the best three will be used to calculate your mark (20 marks each). 1. For a Galvanic cell using the half-reactions: VO2 + (aq) + 2 H+ (aq) + e− → VO+2 (aq) + H2O(l) Eo = 1.00 V Zn+2 (aq) + 2 e− → Zn(s) Eo = −0.76 V (a) Determine the overall balanced cell reaction. 2 VO2 + (aq) + 4 H+ (aq) + 2 e− → 2 VO+2 (aq) + 2 H2O(l) Zn(s) → Zn+2 (aq) + 2 e− ________________________________________________ 2 VO2 + (aq) + 4 H+ (aq) + Zn(s) → 2 VO+2 (aq) + 2 H2O(l) + Zn+2 (aq) (We know the reaction is in this direction because it must be a Galvanic cell, i.e. it must have Eo cell>0) (b) Calculate the standard cell potential (V). Eo cell = 1.00 + 0.76 = 1.76 V