What am I doing wrong?
If a current of 54 A flows into a cell for 45 minutes 30 s, determine the mass of chronium deposited.
My answer:
54 x 2730 s = 147420
147430/96485
= 1.52 mols
m = n x M
=1.52 x 52
= 79.5
I get 1.528 which would round to 1.53 but it won't make that much difference. I think your problem is the molar mass of Cr. 1 F (96,485 coulombs) will deposit 1 equivalent of Cr and 1 eq is molar mas of 52 divided by change in number of electrons. The problem isn't really specific about the nature of the Cr in solution (or perhaps you just didn't include it in your post); however, most electroplated Cr, I think, comes from Cr^+3 in solution. So the change in electrons will be 3 and 06,485 coulombs will deposit 52/3 = ?? grams Cr.
Will this help?
A car bumper is plated with chronium using chronium(III)ions in solution. If a current of 54 A flows into a cell for 45 minutes 30 s, determine the mass of chronium deposited.
Yes. It is Cr^+3 in solution and the half cell is Cr^+3 + 3e ==> Cr.
So the equivalent weight is what I posted in my first response of 52/3 or a little over 17 g for 96,485 coulombs. I get something like 26 grams but that's an estimate.
To determine what you might be doing wrong, let's go through the problem step by step:
1. First, you correctly multiplied the current (54 A) by the time in seconds (45 minutes 30 seconds = 2730 seconds) to get 147420.
2. However, it seems like you made a mistake in the second step. Instead of dividing 147430 by 96485, you should actually be dividing 147420 by 96485. This will give you the number of moles of chromium.
So, the correct calculation would be:
147420 / 96485 = 1.525 moles of chromium deposited.
3. Finally, to find the mass of chromium, you need to multiply the number of moles (1.525) by the molar mass of chromium (52 g/mol).
So, the correct calculation would be:
1.525 moles x 52 g/mol = 79.3 grams (rounded to one decimal place).
Therefore, the correct answer for the mass of chromium deposited would be approximately 79.3 grams.
In summary, it looks like you made a slight calculation error in the division step. Double-check your calculations and use the correct values to get the accurate answer.