UNIT # 7 Introduction Objectives Problems 1 | 2 | 3 | 4 | 5

CALCULATIONS BASED ON FORMULAE

7.5 - Calculations involving Avogadro's number

As chemists, we need to be able to answers questions of this type:

" How many oxygen atoms are there in 5.0 grams of Na2CO3?"

" 5 moles of electrons is equivalent to how many electrons?"

" How much volume does 2.5 moles of CO2 gas occupy at STP?"

Avogadro's number allows us to carrying out calculations between:

1. grams
2. moles
3. number of particles (eg - these can be # of electrons, # of atoms, # of ions, # of molecules ... etc ...)

How do we do this?

• In the next section, section 7.5.1 we will learn how to convert between mass (in grams) and moles.
• In the next section, section 7.5.2 we will learn how to convert between moles and number of particles.
• In the next section, section 7.5.3 we will learn how to convert between mass (in grams) and number of particles.

Place your mouse over the image below to see the content of the sections diagrammatically. Click on the portion of the image to jump to the section.