(a) ____Fe(s) + ____O2 (g) h____ Fe2O3(s)
(b) ____H2 (g) + ____N2 (g) h____NH3 (g)
(c) ____Cl2(g) + ____KBr(aq)h____Br2(l ) +
____KCl (aq)
(d) ____CH4(g) + ____O2(g)h____CO2(g) +
____H2O(l )
To balance chemical equations like the ones given, you need to ensure that the number of atoms of each element is equal on both sides of the equation. Here's how you can balance each equation:
(a) Fe(s) + O2(g) → Fe2O3(s)
In this equation, there is one iron atom on the left side and two on the right side. To balance the iron atoms, put a coefficient of 2 in front of Fe on the left side:
2Fe(s) + O2(g) → Fe2O3(s)
Now, let's look at the oxygen atoms. There are two oxygen atoms on the left side and three on the right side. To balance the oxygen atoms, put a coefficient of 3/2 or 1.5 in front of O2 on the left side:
2Fe(s) + 1.5O2(g) → Fe2O3(s)
To get rid of the fractional coefficient, you can multiply the entire equation by 2:
4Fe(s) + 3O2(g) → 2Fe2O3(s)
(b) H2(g) + N2(g) → NH3(g)
There are two hydrogen atoms on the left side and three on the right side. To balance the hydrogen atoms, put a coefficient of 3/2 or 1.5 in front of H2 on the left side:
1.5H2(g) + N2(g) → NH3(g)
Since you can't have a fractional coefficient, you can multiply the entire equation by 2 to get rid of the fraction:
3H2(g) + 2N2(g) → 2NH3(g)
(c) Cl2(g) + KBr(aq) → Br2(l) + KCl(aq)
There is one chlorine atom on the left side and two on the right side. To balance the chlorine atoms, put a coefficient of 2 in front of KCl on the right side:
Cl2(g) + KBr(aq) → Br2(l) + 2KCl(aq)
Now let's balance the bromine atoms. There is one bromine atom on the left side and two on the right side. To balance the bromine atoms, put a coefficient of 2 in front of KBr on the left side:
Cl2(g) + 2KBr(aq) → Br2(l) + 2KCl(aq)
(d) CH4(g) + O2(g) → CO2(g) + H2O(l)
There are four hydrogen atoms on the left side and two on the right side. To balance the hydrogen atoms, put a coefficient of 2 in front of H2O on the right side:
CH4(g) + O2(g) → CO2(g) + 2H2O(l)
Now let's balance the carbon atoms. There is one carbon atom on the left side and one on the right side, so the equation is already balanced for carbon.
Lastly, let's balance the oxygen atoms. There are two oxygen atoms on the left side and four on the right side. To balance the oxygen atoms, put a coefficient of 2 in front of O2 on the left side:
CH4(g) + 2O2(g) → CO2(g) + 2H2O(l)
Now the equation is balanced, with one carbon atom, four hydrogen atoms, and four oxygen atoms on both sides.