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Impure copper containing Fe, Au, Ag as i...

Impure copper containing Fe, Au, Ag as impurities is electrolytically refined. A current of 140 A for 482.5 s decreased the mass of the anode by 22.26 g and increased the mass of cathode by 22.011 g. Percentage of iron in impure copper is (Given molar mass Fe= 55.5 g `"mol"^(-1)`, molar mass Cu = 63.54 g `"mol"^(-1)`)

A

`0.95`

B

`0.85`

C

`0.97`

D

`0.90`

Text Solution

Verified by Experts

The correct Answer is:
D
The amount of impurity = 22.26 - 22.0111
`=0.259g `
Amount of Cu should have been deposited by a current of
140 a & 482.5 s current `= 140 xx 482.5=67,550 C to ? Cku`
`96,500 C to 31.77 g ` of Cu
`:. 67,500 C to 22.239 g ` pure Cu
But only 22.011 of cathode mass has increased
`:. 22.239 - 22.011 = 0.228g`
Instead of 0.228 g of Cu the amount of Fe oxidised
`0.228 - 31.77`
`? - 27.75`
`= (0.228 xx 27.75)/(31.77) =0.199 g `
`:. % of Fe + (0.199)/(22.26) xx 100`
`=0.89 ~= 0.90`
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Knowledge Check

  • Impure copper containing Fe, Au, Ag as impurities is electrolytically refined. A current of 140 A for 482.5 s decreased the mass of the anode by 22.26 g and increased the mass of cathode by 22.011 g.Percentage of iron in impure copper is (Given molar mass Fe=55.5 mol^(-1), molar mass Cu =63.54 g mol^(-1))

    A
    `0.85`
    B
    `0.90`
    C
    0.95
    D
    0.97

  • Impure copper containing Fe, Au, Ag as impurities is electrolytically refined . A current of 140 A for 482.5 s decreased the mass of cathode by 22.011 g . Percentage of iron in impure copper is . (Given : molar mass Fe = 55.5 " g mol"^(-1) ,molar mass Cu = 63.54 " g mol"^(-1) )

    A
    iron has less afinity for oxygen at high temperature
    B
    sulphur has less affinity for oxygen at high temperature
    C
    copper has more affinity for oxygen than sulphur at high temperature
    D
    copper has less affinity for oxygen than sulphur at high temperature

  • Number of atoms in 588.6 g Fe (atomic mass of Fe = 55.86 g "mol"^(-1) ) is

    A
    twice that in 60 g carbon
    B
    `6.023 xx 10^22`
    C
    half that of 8g He
    D
    `558.6 xx 6.023 xx 10^23`

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