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Byju's Answer

Standard XII

Chemistry

Sodium Thiosulphate

Silver metal ...

Question

Silver metal in ore is dissolved by potassium cyanide solution in the presence of air by the reaction:
$4 A g + 8 K C N + O_{2} + 2 H_{2} O \to 4 K [A g (C N)_{2}] + 4 K O H$
Which of the following is true regarding above reaction?

The amount of KCN required to dissolve 100 g of pure Ag is 120 g

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The amount of oxygen used in this process is 7.40 g (for 100 gm pure Ag)

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The volume of oxygen used at S.T.P is 5.20 litres for the same process

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All of the above

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Solution

The correct option is D All of the above
Number of moles of $A g$ in $100$ g sample $= \frac{100}{108} = 0.925$ .
$4$ moles of $A g$ reacts with $8$ moles of $K C N$ , hence $0.925$ moles of $A g$ will react with $\frac{8 \times .925}{4} \times 65 = 120.25$ g of $K C N$ .

$4$ moles of $A g$ reacts with $1$ mole of oxygen, thus $0.925$ moles will react with $\frac{1 \times .925}{4} \times 32 = 7.40$ g
Volme of oxygen used in the same process $= \frac{1 \times 0.925}{4} \times 22.4 = 5.18 L \approx 5.20 L$

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Silver metal in ore is dissolved by potassium cyanide solution in the presence of air by the reaction:4Ag+8KCN+O2+2H2O→4K[Ag(CN)2]+4KOHWhich of the following is true regarding above reaction?

Silver metal in ore is dissolved by potassium cyanide solution in the presence of air by the reaction:
$4 A g + 8 K C N + O_{2} + 2 H_{2} O \to 4 K [A g (C N)_{2}] + 4 K O H$
Which of the following is true regarding above reaction?