The percentage of copper (II) salt can be determined by using a thiosulphate titration. 0.305g of a copper (II) salt was dissolved in water and added to an excess of potassium iodide solution, liberating iodine according to the following equation
`2Cu^(2+)(aq) + 4I^(-)(aq) rarr 2CuI(s)+ I_(2) ( aq)`
The iodine liberated required 24.5`cm^(3)` of a 0.100 mol` dm^(-3)` solution of sodium thiosulphate.
`2S_(2)O_(3)^(2-) (aq) + I_(2) (aq) rarr 2I^(-) ( aq) + S_(4) O_(6)^(2-) (aq)`
The percentage of copper, by mass, in the copper ( II) salt is

Options

A. 64.2
B. `51.0`
C. 48.4
D. 25.5

Answer

B