Video Transcript
Which of the following equations
correctly shows the thermal decomposition of sodium nitrate? (A) Four NaNO3 solid reacts to
produce two Na2O solid plus four NO gas plus three O2 gas. (B) Three NaNO3 solid reacts to
produce three Na3N solid plus two NO2 gas plus 2.5 O2 gas. (C) Two NaNO3 solid reacts to
produce two Na solid plus two NO2 gas plus O2 gas. (D) Two NaNO3 solid reacts to
produce two NaNO2 solid plus O2 gas.
In order to identify the correct
equation for the thermal decomposition of sodium nitrate, let us clear some
space. To represent this chemical reaction
as a chemical equation, the correct chemical formula of the reactants is written on
the left-hand side followed by an arrowhead pointing towards the right. And the correct chemical formula of
the products is written on the right-hand side of the arrow.
In this problem, the reactant is
sodium nitrate. In order to identify the products,
we need to discuss that sodium nitrate will break down into solid sodium nitrite and
oxygen gas. Now that we know the reactant and
products for this decomposition reaction, we can begin to write the balanced
chemical equation. Let us begin with writing the
chemical formula for sodium nitrate.
The sodium ion has a charge of one
plus, and the nitrate ion is a polyatomic ion that is NO3 with a charge of one
minus. To create a neutral compound, for
every one sodium ion, there will be one nitrate ion. So, the formula would be NaNO3. This is a solid compound, so we
will add the state symbol of s. Now, we will add the arrow in our
chemical equation to separate the reactant from the products.
Now let us write the formula for
sodium nitrite. The sodium ion has a charge of one
plus, and the nitrite ion is NO2 with a charge of one minus. To create a neutral compound for
sodium nitrite, for every one sodium ion, there is one nitrite ion. So, the formula would be NaNO2. We will now add the state symbol of
s since it is a solid.
The other product, oxygen, would
have the formula of O2, since it is diatomic, with the state symbol of g, since it
is a gas.
Since we have created a chemical
equation, let us balance it. When looking at the chemical
equation, we should note that oxygen is not balanced. There are three oxygen atoms on the
reactant side. And on the product side, there are
two oxygen atoms in sodium nitrite and two oxygen atoms in O2, for a total of four
oxygen atoms present. To balance the oxygen atoms, if a
coefficient of two is placed in front of both sodium nitrate and sodium nitrite, six
oxygen atoms will now be present on both the reactant and product side of the
chemical equation. Adding these coefficients also
allowed for sodium and nitrogen atoms to be balanced.
Since we now have a balanced
chemical equation, let us look back at our answer choices from the beginning of the
problem. When looking at the answer choices,
we should notice that answer choice (D) matches the reaction we created in the
video. Therefore, the equation that
correctly shows the thermal decomposition of sodium nitrate is answer choice
(D). Two NaNO3 solid reacts to produce
two NaNO2 solid plus O2 gas.
