5 Let’s now focus on a particular isotope – Carbon-12 1 Carbon-12 atom weighs ______________But this is an impractical measurement. We want to work in the mass unit of grams.So, how many atoms of Carbon-12 would it take to weigh g.?
6 Amadeo Avogadro (Italian, 1776-1856) calculated the number to be 6 Amadeo Avogadro (Italian, ) calculated the number to be x 1023and is also known as aSo now, the average atomic mass number also represents how many grams that element would weigh if you had 1 mole of that substance.
7 So, 1 mole of Water weighs: H: 2 x g/mole = g/moleO: 1 x g/mole = g/moleThis # is known as the _____________(mass of 1 mole) of Water.Examples. Calculate the Molar Mass of the following:a.) SO2b.) (NH4)3PO4
8 Mole to Mass & Mass to Mole Conversions If we are given the # moles of a substance and we want to calculate how much it weighs (i.e. what’s its mass?), then we convert by using the _________________________!E.g. What is the mass of 1.50 moles of Water?1.50 mol. Of H2O x g of H2O = g of H2Omol. of H2OE.g.#2 What is the mass of 0.75 mol. Of Salt?
9 Now, going the other way.How many moles are in 100.g of CO2 ?100.g of CO2 x 1 mol. of CO2 = _______________g of CO2E.g.#2 How many moles are in a pound of Sugar?
10 Converting from moles to molecules & vicy versi In these conversions, instead of using the _________________________, you use Avacado’s Avagadro’s Number. (NA)Ex. How many molecules are in 1.50 moles of Water?(remember: 1 mole = 6.02 x 1023 )1.50 mol. x x 1023 molecules = ___________________mol.Ex.2) How many moles in x 1024 molecules of Salt?2.107 x 1024 molecules x ____ = 3.50 molesx 1023 molecules
11 Do these in-class egg samples: 1.) How many molecules are in 0.02 moles of Sugar?2.) How many moles are in 3.01 x 1023 molecules of O2?Let’s look at lotsof moleculesof Water.
12 Time to draw a MOLE diagram I know what you’re thinking! Now we can doMass to Molecules conversions & vicy versi.(Hint: it’s a 2 step Chain Method)Ex. How many molecules are in 12.0g (~½ oz) of Water?12.0g of H2O x _____________x________________________mol of H2O= 4.00 x 1023 molecules of H2OEx. What does 9.03 x 1022 molecules of Vitamin C weigh?(Vitamin C = C6H8O6)
13 Standard Molar VolumeThe Volume occupied by 1 mole of a gas is the Molar Volume.The Volume occupied by 1 mole of a STP is known as the Standard Molar Volume of a gas and is equal to 22.4 L.STPV = 22.4 L/mol. V = n x 22.4 L/mol.nSo 1 mole of any gas occupies STP, but their masses may be different.
14 So 2 moles of a gas will occupy twice the space (Volume) of 1 mole. e.g. 2H O H2O(more examples: N2 + H2 NH3 ,…)And remember:1 mole = 6.02 x 1023 molecules