Question

The balanced chemical equation for potassium reacting with water is:

• A. $\text{K}\text{(s)}+2{\text{H}}_2\text{O(l)}\to \text{KOH(aq)}+{\text{H}}_2\text{(g)}$
• B. $2\text{K}\text{(s)}+2{\text{H}}_2\text{O}\text{(l)}\to 2\text{KOH(aq)}+{\text{H}}_2\text{(g)}$
• C. $2\text{K}\text{(s)}+{\text{H}}_2\text{O(l)}\to 2\text{KOH(aq)}+{\text{H}}_2\text{(g)}$
• D. $\text{K}\text{(s)}+{\text{H}}_2\text{O}\text{(l)}\to \text{KOH(aq)}+{\text{H}}_2\text{(g)}$

Answer 1

The correct option is B $2\text{K}\text{(s)}+2{\text{H}}_2\text{O}\text{(l)}\to 2\text{KOH(aq)}+{\text{H}}_2\text{(g)}$

Potassium reacts with water to form potassium hydroxide along with hydrogen. The chemical equation for this reaction is given below:

$\text{K}\text{(s)}+{\text{H}}_2\text{O}\text{(l)}\to \text{KOH(aq)}+{\text{H}}_2\text{(g)}$

Given that: Reactant Product

Symbol of elements	No. of atoms	Symbol of elements	No. of atoms
K	1	K	1
H	2	H	3
O	1	O	1

Now, in order to balance the equation, the number of atoms of each element in the reactant and product sides should be equal. So to balance hydrogen atoms, both ${\text{H}}_2\text{O}$ and $\text{KOH}$ are multiplied by 2.
Therefore,
$\text{2K}\text{(s)}+{\text{2H}}_2\text{O}\text{(l)}\to \text{2KOH (aq)}+{\text{H}}_2\text{(g)}$