Lecture 51 Measuring Matter Ozgur Unal NIS – CHEMISTRY Lecture 51 Measuring Matter Ozgur Unal

The Mole The mole, abbreviated mol, is the SI base unit to measure the amount of a substance. A mole is defined as a the number of carbon atoms in exactly 12 g of pure carbon-12. A mole of anything contains 6.0221367 x 1023 representative particles  Avogadro’s number. A representative particle is any kind of particle: atom, molecule, formula unit, electron or ion. Amadeo Avogadro, in 1811, determined the volume of 1 mole of gas. This is why 6.0221367 x 1023 is also called Avogadro’s number.

The Mole 1 mole of Na contains 6.0221367 x 1023 Na atoms. 1 mole of O2 contains 6.0221367 x 1023 O2 molecules. 1 mole of CH4 contains 6.0221367 x 1023 CH4 molecules. 1 mole of NaCl contains 6.0221367 x 1023 NaCl formula unit. 1 mole of electron contains 6.0221367 x 1023 electrons. 1 mole of Mg+2 contains 6.0221367 x 1023 Mg+2 ions. In the rest of the lectures, we will use 6.02 x 1023 as Avogadro’s number.

Converting Between Moles and Particles 1 dozen of rose = 12 roses How many roses are there in 4.5 dozens of rose? 1 mole of representative particles = 6.02 x 1023 representative particles Using this relationship you can convert moles ro representative particles, and reprsentative particles to moles. Example: How many molecules are there in 3 moles of CO2? 3 moles of CO2 = 3 moles of CO2*6.02 x 1023 molecules/1 mole 3 moles of CO2 = 1.806 x 1024 CO2 molecules Example: How many atoms are there in 3.5 moles of Xe. Example: How many moles are there in 3.01 x 1024 ions of Cl-.