How many germs of `K_(2)C_(7)O_(7)` are required to oxidise 20.0g of `Fe^(+)` ion in `FeSO_(4) "to" Fe^(3+)` ions if the reaction is carried out in the acidic medium? Molar mass of `K_(2)Cr_(2)O_(7)` and `FeSO_(4)` are 294 and 152 respectively.

Options

A. 6.45g
B. 7.45g
C. 8.45g
D. 9.45g

Answer

A

Explanation

Number of moles of `FeSO_(4)=((20g))/(152g mol^(-1))`
=0.132mol
Ionic equation for the oxidation reaction carried in the acidic medium may be written as:
`Cr_(2)O_(7)^(2-)+6Fe^(2+)+14H^(+) to 2Cr^(3+)+6fe^(3+)+7H_(2)O`
6 mol. of `Fe^(2+) -= ` 1 mol of `K_(2)Cr_(2)O_(7)`
0.132 mol of `Fe^(2+)-=((1 mol))/((6 mol))xx(0.132 mol^(-1)`
= 0.022 mol . of `K_(2)Cr_(2)O_(7)`
Mass of `K_(2)Cr_(2)O_(7) = (0.022 mol) xx(294 g mol ^(-1))`
= 6.468 g.