One potential source of error is allowing the Cu to coat the Mg turnings ,trapping Mg inside a protective layer of Cu, preventing the Mg from being completely oxidized by the HCI added in step 10. How will this error affect the following calculations ? Briefly explain and for show sample calculations that demonstrate how the experimental error would affect the final results . a] 96 copper ? {6 pts} b] formula mass ? {6 pts}

a) The %Cu will increase. The trapped Mg increases the mass of Cu that is recorded hence giving to increased calculated percentage of the copper in the unknown sample mass.

b) A lower formula mass will be obtained (The calculation in the explanation section is offered as an explanation).

Step-by-step explanation

NOTE: The data above is experimentally obtained since I have similar manual and have done similar experiment. 

a) %Cu = (The mass of Cu formed/Mass of the Cu compound weighed) * 100%

The mass of Cu formed(unknown) = 0.499 g

Mass of Cu compound weighed = 2.063 g

%Cu => (0.499g/2.063g))*100% = 24.19%

%Cu = 24.19%

In case where Mg is trapped in protective layer of copper, the mass of copper recorded becomes greater than 0.499. Assuming that the mass increases to0.550 g, %Cu obtained is calculated as shown below.

%Cu =>  (0.550 g/2.063g)) * 100% = 26.66%

%Cu = 26.66%

Hence, where Mg is trapped in the protective layer of Cu, then the calculated percent copper increases. 

b) Formula mass = (1 Cu atom * 63.55 amu)/%Cu

%Cu => 24.19% = 24.19/100 => 0.2419

Formula mass = (1 Cu atom * 63.55 amu)/0.2419 => 262.71 amu. 

In the case where Mg is trapped in the protective layer of Cu, the calculated percent copper increases to 26.66%

%Cu =>26.66% => 26.66/100 =0.2666

Formula mass = (1 Cu atom * 63.55 amu)/0.2666 => 238.37 amu.