Measuring Matter Section 11.1 Chemistry

Objectives Describe how a mole is used in chemistry. Relate a mole to common counting units. Convert between moles and number of representative particles

Counting Particles A pair is always 2 objects A dozen is 12 A gross is 144 A ream is 500 If I plant 3 dozen roses, how many roses will I have?

Counting Particles Chemists use a counting system that uses a very large number. The mole is the SI base unit used to measure the amount of a substance.

Counting Particles The mole is used to count particles that are very small. –Molecules, atoms, formula units, electrons, or ions. The mole is equal to Avogadro’s number: x This is a HUGE number. –602,000,000,000,000,000,000,000

Converting Moles to Particles and Particles to Moles Suppose you buy 3.5 dozen roses. How many roses do you have? We must go back to conversion factors. 3.5 dozen x 12 roses/1dozen = 42 roses.

Conversion Factor! x representative particles 1 mole

Example Problem If I have 3.5 mol of sucrose, how many molecules of sugar do I have? Start with what you are given in the problem. 3.5 mol of sucrose

Then determine the conversion factor What do you want to end up with? Representative particles Flip the conversion factor so representative particles is on top

Then write your problem out 3.5 mol sucrose x x representative particles 1 mol sucrose 2.11 x molecules of sucrose.

Practice Problems Pg. 311

Assignment Worksheet on Converting Moles to Particles and Particles to Moles