By Mara Pesacreta, Updated Aug 30, 2022

Step 1: Write the Balanced Chemical Equation

Begin by writing the balanced reaction for your experiment. This equation is often provided in the lab manual; if not, write and balance it yourself. For example, the synthesis of sodium chloride is written as:

2 Na + Cl2 → 2 NaCl

Step 2: Measure the Mass of the Product

After the reaction, determine the product’s mass using a calibrated gram balance. In this example, the final mass of sodium chloride is 202.0 g.

Step 3: Calculate the Molar Mass of the Product

Look up the atomic weights of the constituent elements and sum them to obtain the molar mass. For sodium chloride:

• Na: 22.99 g/mol
• Cl: 35.45 g/mol (one atom per formula unit)

Adding these gives a molar mass of 58.44 g/mol for NaCl.

Step 4: Set Up Dimensional Analysis Ratios

Create two conversion factors:

• 202.0 g NaCl × (1 mol / 58.44 g NaCl)
• 1 (to cancel units)

Step 5: Compute the Moles of Product

Multiply the ratios: 202.0 g × (1 mol / 58.44 g) ≈ 3.46 mol of NaCl.

Things Needed

• Periodic table
• Calculator
• Pen
• Paper