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 %#