In this post you will find a step-by-step solution about how to calculate the number of molecules in a product given the mass of a reactant....
In this post you will find a step-by-step solution about how to calculate the number of molecules in a product given the mass of a reactant.
Step 1. Read the problem.
Step 2. Identify the data provided. Rewrite the chemical equation with the corresponding data for each reactant and product.
The mass and molar mass for H2 is given. For N2, the problem states that it is in excess. The latter indicates that H2 is the limiting reactant. The problem asks to determine the number of NH3 molecules produced.
Step 3. Pay attention to the chemical equation. If the chemical equation is balanced you can proceed, but if not it must be balanced before continuing. The reason for having a balanced chemical equation is that the coefficients are used in calculations. If the chemical equation is not balanced or incorrectly balanced the calculations will be erroneous.
Notice that the chemical equation for this problem is already balanced. The information we get from that is that per 3 mol of H2, 2 mol of NH3 is produced. We can rewrite the latter as 3 mol H2 = 2 mol NH3.
Step 4. Determine the number of H2 moles.
Step 5. Convert the moles of H2 determined in step 4 into moles of NH3. You can do this by using the ratio of H2 and NH3 as a conversion factor.
Step 6. Use the relationship of moles and the Avogadro’s number as a conversion factor to calculate the number of NH3 molecules.
