What sequence of coefficients will balance the following equation? #Ca(s) + O_2(g) -> 2CaO(s)#

1 Answer
Jun 13, 2017

Answer:

You place a 2 in front of the #Ca# on the left side of the arrow to make the reaction balanced.

Explanation:

A reaction needs to be balanced in order to fulfil the Law of conservation of mass. Therefore at both sides of the reaction arrow (#->#) we must have the same amount of each atom. The act of doing so is called balancing.

Your reaction is
#Ca+O_2->2 CaO#

The first step to do, is to look how many atoms are on both sides of the arrow.

left side
#1xxCa#
#2xxO# (in #O_2#, there are #2xx O# atoms)

right side
#2xxCa#
#2xxO#

To balance the reaction, we must have on the left side 2 #Ca#-atoms. Therefore we place a 2 in front of the #Ca# on the left side. We obtain:
#2Ca+O_2->2 CaO#

You can see, that we now have 2 atoms of each element at the left and right side of the arrow. Therefore the reaction is balanced!

#color(red)("Please keep in mind:")#
By balancing reactions, you should only set the numbers in front of the molecules (like 2 Ca),
and thus not change the molecules (like #Ca_2# which is a different molecule)
#color(white)(aaaaaaaaaaaaaaaa)/color(white)(a)#