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.
  
  

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Section 8.2
Calculation of Moles of Units. Avogadro's Number (N) ..p189

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