chemistry help please.....

Question

50 mol of 1 M  oxalic acid is shaken  with 0.5 g of wood charcoal .  The final concentration of the solution after adsorption is 0.5 M . What is the amount of the  oxalic acid adsorbed per gram of carbon ?

 

 

1.   3.45  g
2.   6.30  g
3.   3.15  g
4.   none  of the above choices 

Answer 1

I'm going to guess that you meant 50 ml, not 50 mol, since you generally don't measure an amount of solution in moles. 

 

50 ml is .05 liter.  And since the solution is 1 M, that means that there are .05 moles of oxalic acid in it.

 

Oxalic acid is (COOH)₂.  So the molecular mass is:

 

C:  12.011 x 2 = 24.022

O:  15.999 x 4 = 63.996

H:  1.008 x 2 = 2.016

 

TOTAL:  90.034

 

.05 moles of oxalix acid, therefore, is .05 x 90.034 = 4.502 grams.

 

After the mixture is shaken, the concentration of oxalic acid drops by half, so the amount of oxalic acid adsorbed is half the original amount, or 4.502 * 1/2 = 2.251 grams.

 

To find the amount adsorbed per gram of charcoal, divide the amount adsorbed by the amount of charcoal = 2.251 / 0.5 = 4.502.

 

However, that's not what the question is asking.  It asks for the amount of oxalic acid adsorbed per gram of CARBON.  Not all of charcoal is carbon, and the amount of carbon in charcoal depends on what kind of wood the charcoal was made from and how it was made.  So...

 

If the assumption is that the charcoal is pure carbon, then the answer we came up with is none of the given choices, so it would be #4.

 

If that is assumption is not made, then there isn't enough information to solve the problem.