« Return to AACT homepage

AACT Member-Only Content

You have to be an AACT member to access this content, but good news: anyone can join!

Need Help?

Calculating Moles Mark as Favorite (67 Favorites)

LAB in Mole Concept, Dimensional Analysis, Measurements, Molar Mass. Last updated October 28, 2019.

Summary

In this lab, students will have the opportunity to practice conducting the chemist’s way of counting atoms and molecules by using the mole. They will determine the mass of various common elements and compounds and convert this data into values of moles, atoms and molecules. This will allow students to realize the connection between commonly used laboratory chemicals and the quantitative data and calculations that are such a fundamental part of chemistry.

Grade Level

High School

Objectives

By the end of this lab, students should be able to

  • Understand the concept of the mole.
  • Convert mass data for an element or a compound into values of moles, atoms or molecules.

Chemistry Topics

This lab supports students’ understanding of

  • Moles
  • Measurement
  • Dimensional Analysis

Time

Teacher Preparation: 20 minutes

Lesson: 45 minutes

Materials

  • Al (nails)
  • Cu (plumbing elbows)
  • NaCl
  • NaHCO3
  • C12H22O11
  • H2O
  • Any other common elements or compounds
  • Calculator
  • Electronic Scale
  • Periodic table

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Students should wash their hands thoroughly before leaving the lab.
  • When students complete the lab, instruct them how to clean up their materials and dispose of any chemicals.

Teacher Notes

  • The substitute materials can be used instead of those listed for the elements and compounds in this lab (example: Aluminum foil, copper wire, etc.)
  • Students can work individually or with a partner.
  • I encourage students to use dimensional analysis when completing their calculations. Student Activity version B has incorporated NGSS-based science and engineering practices.

For the Student

Background

The chemist’s way of counting atoms and molecules is by using the mole. One mole of any substance is equal to the average atomic mass for an element or average formula mass for a compound. This mass is called the molar mass. One mole of any substance contains Avogadro’s number of particles, 6.022 x 1023 particles. In this lab you will calculate the number of atoms and molecules in a sample containing either an element or a compound. If the sample is an element, you will have one answer, if it is a compound you will have 2 answers.

Materials

  • Al (nails)
  • Cu (plumbing elbows)
  • NaCl
  • NaHCO3
  • C12H22O11
  • H2O
  • Calculator
  • Electronic Scale
  • Periodic table

Safety

  • Always wear safety goggles when handling chemicals in the lab.
  • Wash your hands thoroughly before leaving the lab.
  • Follow the teacher’s instructions for cleanup of materials and disposal of chemicals.

Procedure

  1. Pick up a tray of chemicals from the lab table in the front of the room.
  2. Find the mass of the empty cup and record it at the bottom of the data table below.* Assume all of the cups have the same mass, so you can use this mass to find the mass of the chemical in each cup.
  3. Record the chemical formula written on the cup for each chemical that is on your tray in the data table below.
  4. Find the mass of cup and its contents; record the mass in the data table.
  5. Subtract the mass of the cup to find the mass of only the chemical; record the mass in the data table.
  6. From the formula find the molar mass of the chemical in the cup. Record the molar mass for each formula in the data table.
  7. In the Calculations section use the mass of the chemical and its molar mass to find the number of moles of chemical in the cup. Show all of your work.
  8. In the Calculations section use Avogadro’s number to find the number of atoms in the cup if the chemical is an element or the number of molecules in the cup if the chemical is a compound.
  9. In the Calculations section, if the chemical is a compound, then find the number of atoms in the cup.
  10. When finished put the cups back into the tray and place the tray on the front lab table.

Data

Chemcial Formula Mass of chemical + cup (grams) Mass of Chemical
 		Molar Mass

* Mass of Empty Cup _____________

Calculations

  1. Below use the mass of the chemical and its molar mass to find the number of moles of chemical in the cup. This calculation will be completed for all chemical samples in the data table. Show all of your work.
  2. Below use Avogadro’s number to find the number of atoms in the cup if the chemical is an element or the number of molecules in the cup if the chemical is a compound. This calculation will be completed for all chemical samples in the data table. Show all of your work.
  3. Below, if the chemical is a compound, then find the number of atoms in the cup. This calculation will be completed ONLY for the chemicals converted to molecules in question 2 above. Show all of your work.

Resource updated on 7-22-16 by AACT.