Video Transcript
In the Haber process, ammonia, NH3, is produced from nitrogen and hydrogen according to the shown equation, 𝑥 N2 plus 𝑦 H2 react to produce 𝑧 NH3. Determine the smallest possible whole number values of 𝑥, 𝑦, and 𝑧.
𝑥, 𝑦, and 𝑧 are stoichiometric coefficients, numerical values written before a species in a chemical equation in order to balance the overall reaction. A chemical equation is said to be balanced when the number of atoms of each element is the same on both sides of the reaction. So to determine 𝑥, 𝑦, and 𝑧, we need to balance this chemical equation. Balancing a chemical equation is often a guess-and-check process. But to make this process easier, we can follow a few simple steps. We’ll start by making a list of the number of atoms of each element on both sides of the reaction.
On the reactant side of this equation, there are two atoms of nitrogen and two atoms of hydrogen. On the product side, there’s one atom of nitrogen and three atoms of hydrogen. The number of nitrogen atoms on each side of the reaction equation is unequal, as is the number of hydrogen atoms. So this equation is unbalanced. Next, we can add coefficients in front of any species in the chemical equation to balance the atoms. This step can be repeated multiple times.
To balance the nitrogen atoms, we can place a coefficient of two in front of ammonia on the product side. If one molecule of ammonia contains one nitrogen atom and three hydrogen atoms, then two molecules of ammonia will contain two nitrogen atoms and six hydrogen atoms. The number of nitrogen atoms on both sides of the equation are now equal and balanced. To balance the hydrogen atoms, we can place a coefficient of three in front of the hydrogen molecule on the reactant side of the equation. If one molecule of hydrogen contains two hydrogen atoms, then three molecules of hydrogen will contain a total of six hydrogen atoms. The number of hydrogen atoms is the same on both sides of the reaction equation and is balanced.
As the number of atoms of each element is the same on both sides of the reaction equation, the overall reaction is balanced. Notice that we didn’t need to place a coefficient in front of the nitrogen molecule in order to balance the equation. This means that only one molecule of nitrogen is necessary. Matching up the variables 𝑥, 𝑦, and 𝑧 with the coefficients, we have determined that the smallest possible whole number values of 𝑥, 𝑦, and 𝑧 are 𝑥 equals one, 𝑦 equals three, and 𝑧 equals two.
