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

Jun 7, 2017

$1122 \text{ g CaO}$

#### 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: $C a + {O}_{2} \to C a O$

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:
$\text{ } C a + {O}_{2} \to 2 C a O$

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

$\text{ } 2 C a + {O}_{2} \to 2 C a O$

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 $= 40.078 + 15.999 = \left(56.077 \text{ g CaO")/(1 "mol CaO}\right)$

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

$= 1121.54 \text{ g CaO}$

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