Question

If 20.00 moles of calcium reacted, how many grams of calcium oxide are produced?

Answer 1

`1122" g CaO"`

Explanation:

First you need to create the skeletal equation for the reaction. Since calcium oxide (CaO) is produced, oxygen (`O_2)` is required.

Skeletal equation: `Ca + O_2 -> CaO`

Balance the equation based on the law of conservation of mass. Since there are two oxygen atoms on the left, a `2` coefficient is required:
`" "Ca + O_2 -> 2CaO`

Now you need to have `2` calcium molecules on the left to balance:

`" "2Ca + O_2 -> 2CaO`

This equation is balanced. The equation says that for every two moles of calcium, there are two moles of calcium oxide produced.

The molar mass of CaO `= 40.078 + 15.999 = (56.077" g CaO")/(1 "mol CaO")`

`20.00 " mol Ca" xx (2" mol CaO")/(2" mol Ca") xx (56.077" g CaO")/(1 " mol CaO")`

`= 1121.54 " g CaO"`

If you take into consideration significant figures (SF), the smallest number of SF is 4. This would mean your answer should be `1122 " g CaO"`