How do you calculate percent composition of a mixture?

To get the percent by mass of a mixture, you divide the mass of each component by the total mass and multiply by 100.

##"Percent by mass" = "mass of component"/"total mass" × 100 %##

EXAMPLE:

A mixture contains 1.203 g ##"CaCO"_3## and 1.797 g ##"NaCl"##. What is the percent by mass of each component?

Solution

##"Total mass" = "(1.203 + 1.797) g" = "3.000 g"##

##"% by mass CaCO"_3 = "1.203 g"/"3.000 g" × 100 % = 40.10 %##

##"% by mass NaCl" = "1.797 g"/"3.000 g" × 100 % = 59.90 %##