Chapter 10.1 and 10.2 Calculating atoms

Molar MassIs the same as the atomic weight on the periodic tableElement Examples 12.01 g C = 1 mol C1.01 g H = 1 mol H55.85 g Fe = 1 mol Fe

Molar Mass To find the molar mass of a compound Count the number of each elementMultiply that number by the Average Atomic mass for that element Add all the elements total masses together

Calculate molar mass of magnesium carbonate 24.3 g + 12.0 g + 3 x (16.00 g) =84.3 g/moleSo, 84.3 g/mole = molar mass for magnesium carbonate

ExamplesCalculate the molar mass of:Na2S N2O4

C

Ca(NO3)2

= 78.05 g/mol= 92.02 g/mol= 12.01 g/mol= 164.10 g/mol

What is the mole?Not this kind of mole!

Mole - a word used to represent a large number of objects.Moldy

Avogadros Number: the number of particles in one mole of particles.1 mole particles = 602,000,000,000,000,000,000,000 particles1 mole particles = 6.02 X 1023 representative particles **Memorize this number for the test**

The Mole12 donuts = 1 dozen donuts12 ears of corn = 1 dozen ears of corn6.02 X 1023 particles = 1 mole particles.Molar mass is the mass listed on the periodic table in red rounded to closest whole numberMolar mass = 1 mole atoms = 6.02 X 1023 atoms

What are Representative Particles?The smallest pieces of a substance:molecular compound - moleculeionic compound - formula unit (made of ions)element: is the Remember the 7 diatomic elements? (made of molecules) H2N2O2F2Cl2I2Br2atom

Solving Problems in Chemistry

Required Work for Solving Problems in ChemistryList givenList conversionsStart with given information including proper unitsDetermine the units for your answer.Put in conversions until the last unit is what you are solving for.

Solving Problems in Chemistry

1. How many sulfur atoms are equivalent to 3 moles of sulfur atoms? Given: 3 moles of sulfur atoms = ? Sulfur atomsConversion: 1 mole of sulfur atoms = 6.02 X 1023 sulfur atoms1.806 x 1024 atoms S3 moles S6.02 x 1023 atoms S 1 mole SX=1.806 x 1024 atoms S1

2. How many atoms are present in 3.7 moles of sodium?3.7 moles Na = ? atoms Na 1 mole Na = 6.02 X 1023 atoms Na3.7 moles Na=2.22 X 1024 atoms Na2.22 X 1024 atoms Na1List given:List conversions:Set Up:

3. How many atoms are present in 155 moles of Arsenic?155 moles As = ? atoms As 1 mole As = 6.02 X 1023 atoms As155 moles As=9.33 X 1025 atoms As 9.33 X 1025 atoms As1List given:List conversions:Set Up:

Atoms to Moles

1. How many moles of Xenon are equivalent to 5.66 X 1026 atoms Xe?5.66 X 1026 atoms Xe = ? moles Xe1 mole Xe = 6.02 X 1023 atoms Xe5.66 X 1026 atoms Xe=940.2 moles Xe 6.02 X 10235.66 X 1026 moles XeList given:List conversions:Set Up:

2. How many moles of Silver are equivalent to 2 .888 X 1015 atoms Ag?2.888 X 1015 atoms Ag = ? moles Ag1 mole Ag = 6.02 X 1023 atoms Ag2.888 X 1015 atoms Ag=4.8 X 10-9 moles Ag2.888 X 1015 moles Ag6.02 X 1023List given:List conversions:Set Up:

Moles To Grams

1. moles of sulfur atoms equals how many grams of sulfur? Given: 3 moles S = ? Grams SConversion: 1 mole S = 32 grams S96 grams S3 moles SX=96 grams S132 grams S 1 mole S

2. Find the mass in grams of 8.6 moles bromine8.6 moles Br = ? grams Br 1 mole Br = 80 grams Br8.6 moles Br=688 grams Br 688 grams Br1List given:List conversions:Set Up:

3. Find the mass in grams of 7.55 moles silicon7.55 moles Si = ? grams Si 1 mole Si = 28 grams Si7.55 moles Si=211.4 grams Si 211.4 grams Si1List given:List conversions:Set Up:

Grams to Moles

1. How many moles are in 38 grams of Carbon?38 grams C = ? moles C1 mole C = 12 grams C38 grams C=3.17 moles C 38 moles C12List given:List conversions:Set Up:

2. How many moles are in 2 grams of Hydrogen?2 grams H = ? moles H1 mole H = 1 grams H2 grams H=2 moles H 2 moles H1List given:List conversions:Set Up:

Grams to Particles

Solving Problems in Chemistry

1. 57 grams sulfur is equal to how many atoms of sulfur? Given: 57 grams S = ? atoms SConversion: 1 mole S = 32 grams S1 mole S = 6.02 X 1023 atoms S1.07 X 1024 atoms S57 grams SXX=3.43 X 1025 atoms S326.02 X 1023 atoms S 1 mole S 1 mole S32 grams S

2. How many atoms of Sulfur are in 100 grams of Sulfur?100 grams S = ? atoms S1 mole S = 32 grams S1 mole S = 6.02 X 1023 atoms S100 grams S=1.88 X 1024 atoms S6.02 X 1025 atoms S32List given:List conversions:Set Up:

The Mole-Volume Relationshipgases- hard to determine masshow many moles of gas?2 things affect gas Volume:a) Temp & b) Pressurecompare all gases at = temp & pressure

Standard Temperature and Pressure 0C & 1 atm pressure- abbreviated STP At STP, 1 mol of any gas has V of 22.4 L- Called molar volume 1 mol of any gas at STP = 22.4 L

Density of a gas D = m / V (density = mass/volume)- for gas units are: g / L find density of a gas at STP if formula knownYou need: 1) mass and 2) volume Assume 1 mol, so mass is molar mass (from periodic table) At STP, V = 22.4 L

If given density, find molar mass of gasAssume 1 mol at STP, so V = 22.4 Lmodify: D = m/V to show: m will be mass of 1 mol, given 22.4 Lm = D x V

What is molar mass of a gas with density of 1.964 g/L?How about a density of 2.86 g/L?

= 44.0 g/mol64.0 g/mol

Notice all conversions must go through the MOLE!Copy this conversion map into your notes!

Thats all Folks !

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