Question

Question #117dd

Answer 1

2.9M

Explanation:

• The current passed, `I=10 A`
• The time of passing the current, `t=16 min 5 s=(16xx60+5) s = 965 s`
• So the quantity of electricity passed is

`Q=Ixxt= "10 C·s"^"-1"xx"965 s"="9650 C"="9650 C"/("96500 C·F"^"-1")="0.10 Faraday"`

We know from Faraday's law that the passage of 1 Faraday of electricity accumulates 1 gm-equivalent ions (here `"Cu"^(2+)`)

So, in our case 0.10 gm-equivalent `"Cu"^(2+)` will be deposited.

Since `"Cu"^(2+)`is divalent, the amount of `"Cu"^(2+)` deposited will be

`"0.10 mol"/2="0.050 mol"`
{since `"molar mass" = 2xx "equivalent mass"` or `"1 gm-equivalent" =1/2 "mol"`)

Now, the initial concentration of the solution is 3 M.

Its 0.5 L will contain `0.5xx "3 mol"="1.5 mol Cu"^(2+)`

After deposition of 0.050 mol due to passage of electricity, there will be `"(1.5-0.05) mol"="1.45 mol Cu"^(2+)` in 0.5 L solution.

Hence the final concentration after electrolysis is

`"1.45mol"/"0.5 L"="2.9 M"`