POST-LAB QUESTIONS How would the calculated molar mass of your unknown be affect

Question

POST-LAB QUESTIONS How would the calculated molar mass of your unknown be affected if the following errors were made? Be very clear in your reasoning. a) Some magnesium was filtered out with the precipitated copper. 1. b) A little more acid was added than needed to dissolve the excess magnesium The magnesium was fully dissolved but a bluish color persisted in the solution as was filtered. c) d) Too much magnesium was added but it was all dissolved prior to filtering. PERIMENT 4 I PERCENT COPPER IN A COMPOUND: POST-LAB

Explanation / Answer

a)

If the some of the magnesium is filtered out with the precipitated copper then the amount of the copper recovered would be higher therefore it will give the higher moles of the unknown therefore the mass of the compound would be lower. Because molar mass = mass / moles

so if the moles are more then molar mass is less.

b)

If more acid was added than it is needed to dissolve the magnesium then excess acid will remain in the solution. Therefore the moles of acid used would be higher which will lead to the lower molar mass of the unknown..

c)

If the magnesium is fully dissolved but still the bluish color persist in the solution means all the Cu^2+ ions are not reduced to solid copper hence threes some amount of the copper is still remain in the solution hence moles of the unknown reacted are less means molar mass would be higher. Because less moles means higher molar mass.

d)

If the magnesium was added in excess amount but it get dissolved before the filtration that means all the copper is not precipitated there the moles of the unknown would be lower and hence it will lead to higher molar mass.

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