What is a Mole?

To a chemist a mole is a counting unit for a substance. Abbreviated “mol”

The mass of one MOLE of a pure substance is numerically equal to its ATOMIC MASS (the red number on the PT). We use grams to represent the unit for atomic mass.

EXAMPLES ONE MOLE OF CARBON = grams ONE MOLE OF LITHIUM = grams ONE MOLE OF SODIUM = grams ONE MOLE OF GOLD = grams

DO YOU GET THE IDEA?

Calculate the mass in grams of moles of chromium. Moles Cr x grams Cr = grams Cr mole Cr set up your conversion fraction so that mole Cr will cancel out Sample problem ( Mole to mass conversion)

mol Cr X g Cr = 2.34 g Cr 1 mol Cr (make sure you set up your UNITS so they can cancel out)

Now you work the practice problems on page 316 of text. 11. Determine the mass in grams of each of the following: a)3.57 mol Al c) 3.45 mole Co b) 42.6 mol Si d) 2.45 mol Zn

Mass to Mole Conversions Calcium, the fifth most abundant element on Earth, is always found combined with other elements because of its high reactivity. How many moles of calcium are in 525 grams calcium (Ca)? mass in grams x 1 mole = number of moles mass in grams 525 grams Ca x 1 mole = 13.1 moles grams Ca

PRACTICE PROBLEMS 12. Determine the number of moles in each of the following. a)25.5 g Ag c) 125 g Zn b) g S d) l.00 kg Fe

ANSWERS 11. a) 96.3 g Al c) 203 g Co b) 1.20 x l0 3 g Si d) 1.60 x 10 2 Zn 12. a) mol Ag c)1.91 mol Zn b) mol S d) 17.9 mol Fe

SO NOW YOU KNOW A MOLE

Amedeo Avagadro Was an Italian physicist & lawyer who established that ONE MOLE of ANYTHING contains 6.02 x representative particles.

Avagadro’s Number is 6.02 x particles (particles includes atoms, molecules, ions, formula units)

This is a really big number

Conversion factors: 6.02 x representative particles 1 mole OR ____________1 mole____________ 6.02 x representative particles

moles gramsatoms X 1/ molar mass = X 6.02 x = = 1/6.02 x X = molar mass X X 1/molar mass X 6.02 x = = molar mass X 1/6.02 x X