Question

0.27 - actual value of AlCl2
1.1173 - theoritical value of Alcl2

% Error = [(0.27-1.1173)/1.1173] * 100
= -76 %

What are some reasons for the -76% error. I thought of 2 but i`m not sure if they're right.

- we spilled some of the AlCl2 while the reaction was taking place
- the reaction was not complete

Answer 1

I'm sure you intended to type AlCl3.
Spilling is one.
Most CuCl2 I have seen is wet. If you didn't dry it the mass you weighed may not have been the true mass of the CuCl2.
Also, it is difficult to get dry AlCl3 since AlCl3 is very hygroscopic. If you didn't dry the product the mass you finished with could have been the wrong mass. In this case, however, wet AlCl3 would have caused you to appear to have more than you actually had. That would have led to a + error.

Answer 2

Thanks Dr. Bob :)