Video Transcript
Hydrogen iodide is produced by the reaction of hydrogen and iodine, according to the
following equation: 𝑥H2 plus 𝑦I2 react to produce 𝑧HI. The coefficients 𝑥, 𝑦, and 𝑧 are all whole numbers. What are the smallest possible values of 𝑥, 𝑦, and 𝑧?
Let’s begin by identifying the elements involved in the reaction. Every element has a chemical symbol. And every chemical symbol is either a capital letter or a capital letter followed by
a lowercase letter. What we need to do is look at the chemical equation and break it down into the
individual letter groups. Starting at the beginning of the equation, we can see a capital H. This is a chemical symbol. This chemical symbol appears in two molecules in the equation. We also see a capital I, which appears in two molecules in the equation. Notice that we are ignoring the subscript values for now.
We can make a list of these elements using a periodic table to match the chemical
symbol to the element name. Capital H represents hydrogen, and capital I represents iodine.
Next, we will count the number of atoms of each element on both sides of the
reaction. We can make a chart to help us organize this information. The chart consists of our elements listed down the left-hand side and the chemical
equation written across the top. We can divide the chart in half at the arrow, separating the reactants and
products. Let’s count the hydrogen atoms. On the reactants side, we see two atoms of hydrogen. We can make note of this in our chart. And on the products side, we can see one atom of hydrogen.
We can repeat this process for iodine. We can see two atoms of iodine on the reactants side and one atom of iodine on the
products side. Now we can add coefficients to the chemical equation in order to balance the
reaction. A reaction is balanced when the number of atoms of each element is the same on both
sides of the reaction. We have two atoms of hydrogen on the reactants side and one atom of hydrogen on the
products side. These values are not equal, meaning that the hydrogen atoms are unbalanced.
Likewise, there are two atoms of iodine on the reactants side and one atom of iodine
on the products side. The iodine is also unbalanced. We can place a coefficient of two in front of the hydrogen iodide. Two hydrogen iodide molecules will contain two atoms of hydrogen and two atoms of
iodine. With two atoms of hydrogen on both sides of the reaction, the hydrogen atoms are
balanced. There are also two atoms of iodine on both sides of the reaction, meaning that the
iodine atoms are also balanced. The reaction is balanced with a coefficient of one in front of the hydrogen, one in
front of the iodine, and two in front of the hydrogen iodide.
After balancing the chemical equation, we have determined that 𝑥 equals one, 𝑦
equals one, and 𝑧 equals two.
