Question #3336d

1 Answer
Sep 4, 2017

Answer:

#"CaO"# contains 71.47 % #"Ca"# by mass.

Explanation:

The percent by mass is an intensive property — it does not depend on the amount of substance you have.

The formula for mass percent is

#color(blue)(barul|stackrel(" ")("Mass %" = "mass of component"/"total mass" × 100 %)|)#

Let's assume that we have 1 particle of #"CaO"#.

Then we have 1 atom of #"Ca"# and 1 atom of #"O"#.

We can use the Periodic Table to compute the masses:

#bbul("Atoms"color(white)(m)"Mass/u")#
#color(white)(ll)"1 Ca"color(white)(mmm)40.08#
#ul(color(white)(ll)"1 O"color(white)(lmmm)16.00#
#color(white)(mll)"Total = 56.08"#

#"Mass % Ca" = (40.08 color(red)(cancel(color(black)("g"))))/(56.08 color(red)(cancel(color(black)("g")))) × 100 % = 71.47 %"#