homework help 8618

42.88 % ##”C”## by mass and 57.12 % ##”O”## by mass

Percentage composition is the percentage by mass of each element in a compound.

##”% by mass” = “mass of element”/”total mass of all elements” × 100%##

To find the % composition of ##”CO”##, you calculate the % by mass of each element in a given mass of ##”CO”##. It is simplest to use 1 mol of ##”CO”##.

1 mol ##”CO”## contains 1 mol of ##”C”## and 1 mol of ##”O”##.

28.01 g ##”CO”## contain 12.01 g ##”C”## and 16.00 g ##”O”##.

##”% C by mass” = “mass of C”/”mass of CO” × 100 % = (12.01 color(red)(cancel(color(black)(“g”))))/(28.01 color(red)(cancel(color(black)(“g”)))) × 100 % = 42.88 %##

##”% O by mass” = “mass of O”/”mass of CO” × 100 % = (16.00 color(red)(cancel(color(black)(“g”))))/(28.01 color(red)(cancel(color(black)(“g”)))) × 100 % = 57.12 %##