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Gold dissolves in cyanide solution the p...

Gold dissolves in cyanide solution the presence of air to form `[Au(CN)_(3)]` which is stable in a cons solution.
`Au_((s))+CN_((s))^(-)+O_(2)+H_(2)O_(2) hArr [Au(CN)_(2)]_((aq))^(-)+OH_((aq))^(-)`
Aquaregia a 3 : 1 mixture of conc. HC and `HNO_(3)` was developed by the alchemists as a means to dissolve gold. The process is actually a Redox reaction.
`Au_((s))+NO_(3(aq))+Cl^(-) hArr AuCl_(4(aq))^(-)+NO_(2(g))`
Gold is too noble to react with `HNO_(3)` However gold does react with a waregia becuase the complex `AuCl_(4)^(-)` forms
`Au_((aq))^(+3)+3e^(-) to Au_((s)) E^(theta)=15V to I`
`AuCl_(4(aq))^(-)+3e^(-) to Au_((s))+4Cl_((q))^(-)E^(0)=1V to 2`
How many grams, approximately of NACN are needed to extract 20g of gold from are?

A

20 g

B

`6.5 g`

C

`10 g`

D

`8 g`

Text Solution

Verified by Experts

The correct Answer is:
C
`Au_(2)S+4NaCN hArr underset((x))(2Na[Au(CN)_(2)])+Na_(2)S`
`2Na[Au(CN)_(2)]^(-)+Zn to Na_(2)[Zn(CN)_(4)]+2Au`
`196......2xx197`
`x......20`
`169xx20=x xx 2xx197`
`:.x=(196xx20)/(2xx197)=10 gm`
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Gold dissolves in cyanide solution the presence of air to form [Au(CN)_(3)] which is stable in a cons solution. Au_((s))+CN_((s))^(-)+O_(2)+H_(2)O_(2) hArr [Au(CN)_(2)]_((aq))^(-)+OH_((aq))^(-) Aquaregia a 3 : 1 mixture of conc. HC and HNO_(3) was developed by the alchemists as a means to dissolve gold. The process is actually a Redox reaction. Au_((s))+NO_(3(aq))+Cl^(-) hArr AuCl_(4(aq))^(-)+NO_(2(g)) Gold is too noble to react with HNO_(3) However gold does react with a waregia becuase the complex AuCl_(4)^(-) forms Au_((aq))^(+3)+3e^(-) to Au_((s)) E^(theta)=15V to I AuCl_(4(aq))^(-)+3e^(-) to Au_((s))+4Cl_((q))^(-)E^(0)=1V to 2 Calculate the formation constant approximately, of Auct at 25^(@)C

Gold dissolves in cyanide solution the presence of air to form [Au(CN)_(3)] which is stable in a cons solution. Au_((s))+CN_((s))^(-)+O_(2)+H_(2)O_(2) hArr [Au(CN)_(2)]_((aq))^(-)+OH_((aq))^(-) Aquaregia a 3 : 1 mixture of conc. HC and HNO_(3) was developed by the alchemists as a means to dissolve gold. The process is actually a Redox reaction. Au_((s))+NO_(3(aq))+Cl^(-) hArr AuCl_(4(aq))^(-)+NO_(2(g)) Gold is too noble to react with HNO_(3) However gold does react with a waregia becuase the complex AuCl_(4)^(-) forms Au_((aq))^(+3)+3e^(-) to Au_((s)) E^(theta)=15V to I AuCl_(4(aq))^(-)+3e^(-) to Au_((s))+4Cl_((q))^(-)E^(0)=1V to 2 The function of HC is to provide C what is the purpose of the Cr in the above reaction select your choice from the following.

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