Calculating Percent Nickel in DMG-Ni Complexes: Where Did I Go Wrong?

[maknott]

What I need to figure out:
We did a gravimetric analysis lab and I have masses for the DMG-Ni complexes that we recovered but I need to find the percent nickel in each sample.
Relevant Equations: I believe you take the mass of the DMG-Ni complex sample and multiply that by the mass ratio of Ni2+ over the FW of DMG. Then divide the result by the mass of the sample and multiply by 100%.

The Attempt at a Solution

I did what I layed out above but I get the same percentage Ni2+ for each sample which doesn't make sense so I must have gone wrong. Any help would be great![/B]

 

[Borek]

Please elaborate on the whole experimental procedure you followed.

multiply that by the mass ratio of Ni2+ over the FW of DMG.

Close, but incorrect. It is not about just DMG, but about molar mass of the whole complex (precipitate).

 

[maknott]

Right, I see so I use the molar mass of the Ni-DMG comlplex (288.9146g).

We basically used DMG and Ni2+ to form a complex and precipitate that out. From this we can determine the percent error by using the Ni2+ that we started with to find the accepted true value for the amount of nickel that we started with.

 

[Borek]

You have still not explained why getting the same percentage Ni²⁺ for each sample doesn't make sense.