Silver metal in ore is dissolved by potassium cyanide solution in the presence of air by the reaction
`4 Ag + 8KCN +O_(2)+2H_(2)O rarr 4K[Ag(CN)_(2)]+4KOH`

Options

A. The amount of KCN required to dissolve 100g of pure Ag is 120g
B. The amount of oxygen used in this process is `0.742g`
C. The mount of oxygen used in this process is `7.40g`
D. The volume of oxygen used at STP is `5.20` lit.

Answer

A, C, D

Explanation

`4Ag +8KCN +O_(2)+2H_(2)Orarr 4K [Ag(CN)_(2)] +4KOH`
`rArr 4 xx 108g` of Ag reacts with `8 xx 65g` of KCN
100g of Ag reacts with `(8 xx 65)/(4 xx 108) xx 100 = 120`
Hence to dissolve 100g of Ag, the amount of `KCN` required `=120g`
Hence, statement (A) is correct
`rArr 4 xx 108g` of Ag require `32g` of `O_(2)`
`rArr 100g` of Ag require `=(32 xx 100)/(4 xx 108) = 7.14g`
Hence, choice (C) is correct
Hence, volume of `O_(2)` required
`= (7.4)/(32) xx 22.4 = 5.20 =` litre
Hence (A),(C),(D) are correct while (B) is incorrect.