(4) (22 pts) Gold metal dissolves in aqua regia, which is a mixture of concentrated hydrochloric and concentrated nitric acids, but gold does not dissolve in either acid separately. (You may write net ionic equations in this problem.) (a) (6 pts) Write a balanced chemical equation for the reaction of gold and nitric acid to produce Au(aq) and nitric oxide. Calculate the standard emf (in V) for this reaction. Is this reaction spontaneous under standard conditions at 25°C? (b) (6 pts) Write a balanced chemical equation for reaction of gold and hydrochloric acid to produce AuCl(aq) and hydrogen gas. Calculate the standard emf (in V) for this reaction. Is this reaction spontaneous under standard conditions at 25°C? (c) (6 pts) Write a balanced chemical equation for reaction of gold and aqua regia, i.e., a mixture of nitric acid and hydrochloric acid, to produce AuCl(aq) and nitric oxide. Calculate the standard emf in V) for the reaction in (e). Is this reaction spontaneous under standard conditions at 25°C? (d) (4 pts) Concentrated nitric and hydrochloric acid have [H]> 1.0M (or [H:0*]> 1.0M). As [H') increases, the emf values for the reactions in (a), (b), and (c) all become more positive (or less negative) in value. From this information and your answers to (a), (b), and (c), briefly explain why aqua regia dissolves gold, but that the two separate acids do not. Useful Information Half-reaction E (V) 0.00 +0.79 +0.96 2 H*(aq) + 2 H2(g) NO3(aq) + 2 H(aq) + NO2(g) + H2O(1) NO;" (aq) + 4 H(aq) +36 - NO(g) + 2 H2O(1) AuCl4- (aq) + 3 - Au(s) +4 Cl(aq) HNO3(aq) + H+ (aq) + 2 NO(g) + H2O(1) NO2(aq) + H+ (aq) + HNO3(aq) Au(aq) + 36 - Au(s) +1.00 +1.00 +1.12 +1.50

Au t HNe Aut3 +NO vedochon hale veachcn +5 Consider Cbalance o Hog+3Ht Ho +3Ht t 2e Not 240 eed 2096 veauron E halk Ox1datlan Aut3 Au t3e ved -1-00V vedualen vea chhon oxldation mulhply e's ১1 2 balance veacton 3A0t 2A3 + 2AU t 3HN + 9 2AU 3Ne t 12 +a40 +640 3No +2AUT3 Oxd Pote na aialatnon ha veao ved 96V- 1-50V not Spontane aus under Shandavd condnda Ex15 neagave, So ANC Au+YHC) +2H CD eaa Auc half veao1an Caa Oxldaran G i-1Oov oxd ve dochan halc veatn O0ov खट O0av-100V -1-00V Sponkane ous So Auc +No Ctn Auc No Co) Au+2HtNo Oxndakn Aumber method mulply Cand calkh 3 2 AU tH t 3 +8 2AUC 3N t 6 H,0 ca6t0 So bul ancel eawahn +12 t 3Nc 8c 2 AU 2ANC 3NOt 6H0 2N304+640 Mdahin half veachan AUCI 3e &AU CS -1-00 reduchon haif-veaCon NO 44t41e GYed eo-960 6-96u 1-00 noh SponkaneouS Condns undev Standavd vn & For rxn at Cave sol nauias CooCau nok nclut CAUClyCH Cलपटब्लप a Far vea.cknc CaucCo C అ(( tthen Ancreases evm RT na hecarmes pasikve Move So 7 emf Vesues ccone mave pasikave -2303 Rr CH ncreaei CHT) So ave tess negahe For negatlve 7S less Oaua vegan see mixhve and Hcl Cor and becomes posve CH, C CA moves Enror skandov Rయ he two renaing For veachanr Hese move efarmes ncreases CA ndke and Vn much han veaclen gad Issolves go posihe oh a vega 0qya vegla PosIAve SO csin Mgher becones as .

(4) (22 pts) Gold metal dissolves in aqua regia, whic…

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Au t HNe Aut3 +NO vedochon hale veachcn +5 Consider Cbalance o Hog+3Ht Ho +3Ht t 2e Not 240 eed 2096 veauron E halk Ox1datlan

Oxd Pote na aialatnon ha veao ved 96V- 1-50V not Spontane aus under Shandavd condnda Ex15 neagave, So ANC Au+YHC) +2H CD eaa

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(4) (22 pts) Gold metal dissolves in aqua regia, which is a mixture of concentrated hydrochloric...

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