Dimensional Analysis 1. Determine what your final unit needs to be - "what do you want" 2. Determine what unit you've been given - "what do you have" 3. Set up a ratio so your units cancel - usually: want on top / have on bottom EX: How many minutes are in a day? How many seconds?

Moles Called the “chemist’s dozen” A really big quantity to measure really tiny things x particles per mole Can measure atoms, molecules, formula units, ions, electrons, etc. Allows us to convert from particles to mass (grams) or grams to particles

A mole of …… Marbles would cover the earth to a depth of 6 km. Glasses of water would fill the earth’s oceans. Sand grains would fill all the beaches in the world. Paper clips would stretch to the nearest galaxy 2 million light years away.

Try It 1.Determine the number of atoms in 2.50 mol Zn. 2.Given 3.25 mol AgNO 3, determine the number of formulas units. 3.Calculate the number of molecules in 11.5 mol H 2 O

Answers mol Zn x 6.02 x atoms/mol = 1.51 x atoms Zn mol AgNO 3 x 6.02 x formula units/mol = 1.96 x formula units AgNO mol H 2 0 x 6.02 x molecules/mol = 6.92 x molecules H 2 0

Try It How many moles are each of the following? x atoms Al x formulas units ZnCl 2

Answers x atoms Al x 1 mole/6.02 x atoms = 9.55 mol Al x formulas units ZnCl 2 x 1 mole/6.02 x formula units =.595 mol ZnCl 2

Mass & the Mole Which would weigh more a mole of helium or a mole of lead? WHY? Atomic mass = amu / atom Molar mass = grams / mole Chromium has an atomic mass of amu so its molar mass = grams How much would 2 moles of Cr weigh? How much would.0450 moles weigh?

Try It Determine the mass in grams of each of the following: 3.57 mol Al42.6 mol Si Determine the number of moles in each of the following: 25.5 g Ag300.0 g S

Answers mol Al x g/mol = 96.3 g Al mol Si x g/mol = 1200 g Si g Ag x 1 mol/ g =.236 mol Ag g S x 1 mol/ g = mol S

Ratios to Know 1 mole = 6.02 x 1023 particles / atoms / etc 1 mole = X grams (determine X using the periodic table)