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

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SUMMARY

The discussion centers on calculating the percent nickel in DMG-Ni complexes using gravimetric analysis. The correct method involves using the molar mass of the entire Ni-DMG complex (288.9146 g) rather than just the mass ratio of Ni2+ to the formula weight of DMG. Participants emphasize the importance of considering the total mass of the precipitate to accurately determine the nickel percentage. The issue of obtaining the same percentage for different samples indicates a potential error in the experimental procedure or calculations.

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maknott
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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]
 
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Please elaborate on the whole experimental procedure you followed.

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

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