By the use of "grouping" (we call it the mole concept in chemistry) of base units or particles of substances that are too small and numerous to mass out or count individually, we can actually do these tasks. So far, one has been limited to the following calculations:

- Mass to mole or mole to mass
- Volume of any gas at STP to mole or visa versa
- Number of particles (a general name) to moles or visa versa

A graphic organizer called the [Mole Wheel Handout] or [Level 2 Mole Wheel] has been used to help in determining the appropriate equation/conversion factor for the problems. Using the Mole Wheel, one sees that all the One Step Calculations are calculations that either goes from the outside of the wheel (on one spoke of the wheel) to the mole (the hub of the wheel) or visa versa.

The next logical question is, Why is one limited to go from the spoke (mass, or number of particles, or volume) to the hub (the mole)? Why can't one go from one spoke to another spoke?

For example, why can't one ask the question, What is the mass of 42.5L of CO_{2} gas at STP?

Of course, the answer is one can answer this question. Here, it is called a **Two Step Mole Calcuations.**

The procedures for Two Step Mole Calculation (using the Mole Wheel as guide) are the same as any math problem in class and just an extension of One Step Mole Calculation.

The step are the following:

1. From problem/question, find known information (locate on Mole Wheel)

2. From problem/question, find what one is looking for (locate on Mole Wheel)

- 2a. Set up calculation either by equation or Dimensional Analysis to go from know info to mole

- 2b. Then do the same from mole to information one is looking for.

Here is:

- An example of a Two Step Mole Calculation (using above procedures), [Example of Actual Calculations for Two Step Mole Problem]
- [You Tube Video on Notes on Two Step Mole Calculations] If you are using Edpuzzle, name is Chem328VideoNotesonTwoStepMoleCalculation.
- HW: Initial Two Step Problems

- [You Tube Video of Two Step Mole Calculation, Actual Doing Work Real Time]. If you are using Edpuzzle, name is 2020Chem328TwoStepMoleCalculationDoingWorkPPTVideo.
- [Powerpoint Presentation for Two Step Mole Calculation Actual Doing Work Real Time]. If you want to take notes as you watch above video, print out this document.