What is the percent composition of calcium (Ca) in CaO?

A 56g/40g x 100%

B 16g/56g x 100%

C 40g/56g x 100%

D 40g/100% x 56g

its either a or c but im not certain just try putting both of those in google to narrow the results.

C 40 g/56 g * 100 %

Explanation:

Calculate the mass of each component and the total mass.

Element Atomic mass/u No. of atoms Subtotal mass/u

Ca 40.08 1 40.08

O 16.00 1 16.00

Total = 56.08

The formula for mass percent is

% by mass = Mass of component/Total mass * 100 %

In this problem

% Ca = mass of Ca/mass of CaO * 100 %

% H = 40.08 g/56.08 g * 100 %