Video Transcript
What is the correct balanced
chemical equation of the reaction of Na metal and water?
In order for us to solve this
problem, let us first identify the reactants in the chemical reaction, which are
sodium metal, Na, and water, H2O. In order to determine the products,
we need to visualize water as H-OH. In this single replacement
reaction, the elements and ions that can form positive charges, such as cations —
which are sodium, Na, and hydrogen, H — will swap places with each other. Therefore, one of the products is a
chemical where the sodium ion with a charge of one plus and the hydroxide ion with a
charge of one minus will form a chemical bond.
When the charges are crossed and
the plus and minus signs are dropped, this chemical formula is NaOH, sodium
hydroxide. The other product is hydrogen gas,
which is H2 since it is diatomic, meaning two atoms of the same element are
chemically bonded together.
Now that we have a chemical
equation, we can work on balancing it. In order to balance a chemical
equation, we need to remember that the law of conservation of mass must be applied,
which states that atoms cannot be created nor destroyed. That means that the number and type
of atoms on the reactant side must equal the number and type of atoms on the product
side.
In order to balance this chemical
equation, coefficients are used, which are numbers placed in front of a chemical
symbol or formulas to show the number of molecules present. We should think of these
coefficients as multipliers.
Within this chemical equation, let
us first notice that the hydrogens are not balanced. We begin with two hydrogen atoms on
the reactant side on the left and three hydrogen atoms on the product side to the
right.
In order to balance the hydrogen
atoms, let us place a coefficient of two in front of NaOH, sodium hydroxide. By placing a coefficient of two in
front of NaOH, this means we have two sets of NaOH formula units. Therefore, we have two hydrogen
atoms in sodium hydroxide and two hydrogen atoms from the hydrogen gas for a total
of four hydrogen atoms on the product side.
When looking at the reactant side,
if we place a coefficient of two in front of the H2O, water molecule, we will now
have two sets of H2O molecules. Therefore, there are four hydrogen
atoms on the reactant side. And the hydrogen atoms are now
balanced on both the reactant and product side of the chemical equation.
Now let us move on to balancing the
oxygen atoms. On the reactant side, in two H2O,
there are two oxygen atoms, and on the product side, in two NaOH, there are two
oxygen atoms. The oxygen atoms have already been
balanced when balancing the hydrogen atoms.
The last element we need to balance
is sodium, Na. On the product side in two NaOH,
there are two sodium atoms, and on the reactant side, there is one in Na. If we place a coefficient of two in
front of Na on the reactant side, both the reactant and product side have two sodium
atoms. Now, all the number and types of
atoms on both the reactant and product sides are balanced.
Therefore, the correct answer for
the balanced chemical equation of the reaction of Na metal and water is two Na solid
plus two H2O liquid yields two NaOH aqueous plus H2 gas.