Question

A 100 gram sample of a mixture was known to contain calcium carbonate and something else, if the sample was reported to contain 45% calcium which of the following could be the other substance in the mixture?

A) NaCl

B) CaO

C) CaI₂

D) Na₂CO₃

I know the answer is B but I don't know how they got that answer. I need someone to show me how they work it out.

Answer 1

The remaining percentage is 100%-45%=55% which is almost equal to percentage mass of CaO$=56/100\times 100=56\%$

So the other substance is CaO