We can calculate the molecular mass of Vitamin C as follows:
29 color(red)(cancel(color(black)("atoms C"))) × "12.01 u"/(1 color(red)(cancel(color(black)("atom C")))) = "348.29 u"
50 color(red)(cancel(color(black)("atoms H"))) × "1.008 u"/(1 color(red)(cancel(color(black)("atom H")))) = "50.40 u"
2 color(red)(cancel(color(black)("atoms O"))) × "16.00 u"/(1 color(red)(cancel(color(black)("atom O")))) =color(white)(l) "32.00 u"
"TOTAL"color(white)(mmmmmmmm) = "430.69 u"
The mass percentages of each element are:
"% C" = (348.29 color(red)(cancel(color(black)("u"))))/(430.69 color(red)(cancel(color(black)("u")))) × 100 % = 80.87 %
"% H" = (50.40 color(red)(cancel(color(black)("u"))))/(430.69 color(red)(cancel(color(black)("u")))) × 100 % = 11.70 %
"% O" = (32.00 color(red)(cancel(color(black)("u"))))/(430.69 color(red)(cancel(color(black)("u")))) × 100 % =color(white)(ll) 7.43 %