Bellwork

Solve the following using dimensional analysis and place the answer in scientific notation.

1. Jamie has 2.5 liters of mercury in a jar. What is the mass of this mercury if its density is 13.6 g/ml?

The mole (mol) is one of the

seven base units in the SI system.

It measures the amount of

substance.

The form in which a substance exists is its “representative particle”.Representative particles can be atoms, ions, molecules, formula units, or anything else.

Just as one dozen is 12 representative particles of eggs, a mole is 6.02 x 1023 representative particles.

602,000,000,000,000,000,000,000!!!!!

Examples:1 mole Fe = 6.02 x 1023 atoms of Fe

1 mole H2O molecules = 6.02 x 1023 molecules of water

1 mole NaCl formula units = 6.02 x 1023 NaCl formula units

1 mole eggs = 6.02 x 1023 eggs

You can have a mole of ANYTHING!!

6.02 X 1023 Watermelon Seeds: Would be found inside a melon slightly larger than the moon.6.02 X 1023 Donut Holes: Would cover the earth and be 5 miles (8 km) deep.6.02 X 1023 Pennies:Would make at least 7 stacks that would reach the moon.6.02 X 1023 Grains of Sand: Would be more than all of the sand on Miami Beach.6.02 X 1023 Blood Cells: Would be more than the total number of blood cells found in every human on earth.

How much is a mole?

Question

• How many molecules would be in 3 moles of water?

Diatomic ElementsCertain elements are only stable in pairs or with other elements in a compound. These elements are called the diatomic elements.

There are 7 diatomic elements:

Bromine, Iodine, Nitrogen, Chlorine, Hydrogen, Oxygen, and Fluorine

(Memory trick: HBrONClIF or 7th Heaven)

Avogadro’s Number

*6.02 x 1023 is called Avogadro’s number. *It is named after Amadeo Avogadro who did work in the 1800’s that allowed 6.02 x 1023 to be calculated.

The mole is the “chemist’s dozen”. It is a convenient way to count extremely large numbers of atoms, molecules or ions.

New Conversion Factor! 1 mole = 6.02 x 1023 representative particles

We work these problems using dimensional analysis.

How many moles are 1.20 x 1025 atoms of phosphorous?

1.20 x 1025 atoms P 1 mol P 6.02 x 1023 atoms

= 19.9 mol P

How many atoms are in 0.750 mol of Zn?

0.750 mol Zn 6.02 x 1023 atoms Zn = 1 mol Zn

4.52 x 1023 atoms Zn

How many molecules are in 0.400 mol N2O5?

0.400 mol N2O5 6.02 x 1023molecules = 1 mole N2O5

2.41 x 1023 molecules

Q: What did Avogadro teach his students in math class?

A: Moletiplication

How many moles are contained in 1.20 x 1024 molecules CO2?

1.20 x 1024 molec CO2 1 mol CO2

6.02 x 1023 molecules

= 1.99 moles CO2

Question

• Your friend gives you a gold ring that contains 2.3 mol of atoms. How many atoms is this?

Gram atomic mass (gam) -atomic mass of an element in grams-mass of one mole of atoms of a monatomic element

Question

• Write the atomic masses of the following.

• Mg __________

• Cl ___________

• Ba ___________

Example:C =12.0 g = mass of 6.02 x 1023atoms 12.0 g/mol is the gram atomic mass of carbon

•Molar mass (M.M.) is a term used to describe the mass of a mole of a chemical compound.

Molar Mass (M.M.)-mass of one mole of any compound-sum of the atomic masses of each atom in the compound

1 mol H2O: 2 mol H 1 mol O

=2 mol H x 1.008 g H/mol = 2.016 g =1 mol O x 15.999 g O/mol= 15.999 g 18.015 g H2O

Question

• What is the gram molecular mass of P2O5?

What is the molar mass of CH3OH?

C 1 x 12.011 = 12.011H 4 x 1.008 = 4.032O 1 x 15.999 = 15.999 32.042 g

Quiz day

• Get ready for your quiz!!!

• Test on Wednesday!

What is the M.M. of magnesium phosphate?

Mg3(PO4)2

3 mol Mg 3 x 24.305 g = 72.915 g

2 mol P 2 x 30.974 g = 61.948 g

8 mol O 8 x 15.999 g =127.992 g

262.855 g

What is the molar mass of ammonium sulfate?

(NH4)2SO4

2 mol N 2 x 14.007 = 28.014 8 mol H 8 x 1.008 = 8.064 1 mol S 1 x 32.066 = 32.066 4 mol O 4 x 15.999 = 63.996 132.14 g

Mole – Mass Conversions

New Conversion factor!

1 mol = molar mass ( grams)

Find the mass in grams of 3.32 mol of K.

3.32 mol K 39.098 g K 1 mol K

= 1.30 x 102 g K

Find the mass in grams of 15.0 mol of sulfuric acid.

H2SO4

H 2 x 1.008 = 2.016S 1 x 32.066 = 32.066O 4 x 15.999 = 63.996 98.078 g

15.0 mol H2SO4 98.078 g H2SO4

1 mol H2SO4

= 1470 g H2SO4

Find the number of moles in 11.0 g of methane (CH4).

CH4 = (12.011g + 4.032g = 16.043 g)

11.0 g CH4 1 mol CH4

16.043 g CH4

= 0.686 mol CH4

What was Avogadro’s favorite Indian tribe?

The MOLEHICANS

Bellwork

What is the molar mass of methane? Methane’s formula is CH4

Molti-Step Mole Problems!

• Calculate the number of molecules present in 4.29 g of nitrogen dioxide (NO2).

• 4.29 g NO2 1 mol NO2 6.02x1023 m.c. NO2=

46.005 g NO2 1 mol NO2

= 5.61x1022 molecules NO2

• Calculate the number of moles of sulfur atoms present in 2.01 g of sodium sulfide (Na2S).

• 2.01 g Na2S 1 mol Na2S 1 mol S atoms

78.046 g Na2S 1 mol Na2S

= 0.0258 mol S atoms

Molti-Step Mole Problems!

• Calculate the mass in grams of 2.49 x 1020 carbon dioxide (CO2) molecules.

2.49 x 1020 CO2 m.c. 1 mol CO2 44.009 g CO2

6.02x1023 m.c.CO2 1 mol CO2

= 1.82 x 10-2 grams CO2

Molti-Step Mole Problems!

• Calculate the grams of carbon in 12.2 mol sucrose, C12H22O11.

12.2 mol C12H22O11 12 mol C atoms 12.011 g C

1 mol C12H22O11 1 mol C atoms

= 1.76 x 103 g carbon

Molti-Step Mole Problems!

Question

• Write the two conversion factors we have discussed below. Show how they are related.

Molar Volume of a GasThe volume of a gas is usually measured at 0oC and 1 atmosphere of pressure.

This is called standard temperature and pressure (STP).

-At STP, one mole of any gas has a volume of 22.4 L which is called the molar volume of a gas and contains 6.02 x 1023 particles of the gas.

-22.4 L of a gas has a mass equal to the gfm of the gas.

-So…1 mol = 22.4L = 6.02 x 1023 particles = M.M.

New conversion factor!

1 mol of any gas at STP = 22.4 L

(for gases only)

What is the volume (liters) at STP of 0.960 mol of methane, CH4?

0.960 mol CH4 22.4 L CH4

1 mol CH4

=21.5 L CH4

At STP, how many moles are in 0.542 mL of neon gas?

0.542 mL Ne 1 L Ne 1 mol Ne 1000 mL Ne 22.4 L Ne

= 2.42 x 10-5 mol Ne

Question

• Relate the three conversion factors we have learned below.

Bellwork

• Jake has a jar full of sodium hydrogen carbonate, or baking soda (NaHCO3). What is the mass of 2.78 mol baking soda?

Bellwork

• How many propane molecules are in 25.00 g of propane, C3H8?

Percent Composition(remember: percent = part divided by total x 100)

percent by mass of each element in a compound

What is the percent composition of NO2?

NO2

N 1 x 14.007 = 14.007 O 2 x 15.999= 31.998

( /46.005g)x100 =30.4%Ca

( /46.005g)x100 =69.6% C

46.005 100%

As long as your % adds up to 99-101% you are fine.

Why is Avogadro so rich!

Because he is a multi-mole-ionairre!!!!

What is the percent composition of calcium acetate?

Ca(C2H3O2)2

Ca1 x40.078=40.078C 4 x12.011=48.044H 6 x 1.008= 6.048O 4 x15.999=63.996 158.166 g

( /158.166g)x100=25.3% Ca( /158.166g)x100=30.4% C( /158.166g)x100=3.8% H( /158.166g)x100=40.5% O 100.0%

Calculate the number of grams of calcium in 9.7 g of calcium acetate?

Ca(C2H3O2)2Ca 25.4%C 30.4%H 3.8%O 40.5%

9.7 g Ca(C2H3O2)2

100 g Ca(C2H3O2)2

25.4 g Ca = 2.46 g Ca

Bellwork

• Susannah has 12.5g of HC2H3O2, or vinegar. How many MOLECULES of vinegar does she have?

CALCULATING EMPIRICAL FORMULAS

Empirical formula - lowest whole number ratio of the elements in a compound- may or may not be the same as the molecular formula.

Steps to calculate empirical formula:1. Find moles of each element.2. Set up mole ratio.3. Simplify mole ratio (divide by smallest). If your answers are not in whole numbers, you must multiply by 2,3,4,or 5 to get whole numbers.4. Use mole ratio as subscripts in the formula. If given % composition, assume 100 g of compound.

Empirical Formula Poem

Percent to mass,

mass to moles,

divide by smallest and

round ‘till whole!

A compound is 79.8% C and 20.2% H. Find its empirical formula.

79.8gC 1mol C = 6.65 mol C 12.011 g C 20.2 g H 1 mol H = 20.0 mol H 1.008 g H

CH3

/6.65 = 1

/6.65 = 3

Find the empirical formula for a compound made up of 26.7% P, 12.1% N and 61.2% Cl.

26.7 g P 1 mol P = 0.862 mol P 30.974 g P

12.1 g N 1 mol N = 0.864 mol N 14.007 g N

61.2 g Cl 1 mol Cl = 1.73 mol Cl

35.453 g Cl

/0.862=1

/0.862=1

/0.862=2

Empirical Formula = PNCl2

Bellwork

• NutraSweet is 57.14% C, 6.16% H, 9.52% N, and 27.18% O.  Calculate the empirical formula of NutraSweet.

Molecular formulas are the actual formulas. They may be the same as the empirical formula or a multiple of it.

To find the multiple (n), take the molar mass (M.M.) and divide by the empirical formula mass (efm):

n = M.M. efm

Multiply each subscript in the empirical formula by n to get the molecular formula.

A white powder is analyzed and found to have the empirical formula P2O5. The compound has a molar mass of 283.9 g. What is the compound’s molecular formula?

P2O5 = 141.898 g/mol

M.M./efm

283.9 g/mol141.898 g/mol = 2

2(P2O5) = P4O10

A compound used as an additive for gasoline to help prevent engine knock shows the following percentage composition: 71.65% Cl 24.27% C 4.07% HThe molar mass is known to be 98.96 g. Determine the empirical formula and the molecular formula for this compound.

71.65 g Cl 1 mol Cl = 2.02 mol Cl 35.453 g Cl24.27g C 1 mol C = 2.02 mol C 12.011 g C4.07g H 1 mol H = 4.04 mol H 1.008 g H

1:1:2 ClCH2 or CH2Clefm = 12.011+2.016+35.453=49.48

g/mol98.96/49.48=2 C2H4Cl2

/2.02 = 1

/2.02 = 1

/2.02 = 2

Hydration

• Water of hydration – water in a crystal– When copper (II) sulfate is

dissolved in water and then the water allowed to evaporate, copper (II) sulfate pentahydrate is formed

– CuSO4 + 5H2O ↔ CuSO45H2O

• Hydrate - compound that contains water of hydration

The picture above shows copper (II) sulfate pentahydrate. Notice the water molecules surrounding the copper molecules.

Hydration

• When cobalt (II) chloride is dissolved in water and then the excess water is allowed to evaporate, cobalt (II) chloride hexahydrate is formed

↔ CoCl2 6H2O CoCl2 + 6H2O

In the hydrate CuSO4.5H20, how

many water molecules would be present in 3 formula units?

Naming Hydrates

• To name a hydrate, use the following:– They are named by giving the name of the salt

followed by a prefix that stands for the number of water molecules associated with a formula unit of the salt.

• Ex: CuSO4 • 5H2O

copper (II) sulfate pentahydrate

Bellwork

• How many moles of each substance are contained in the following samples? Be sure to include the correct units and sig figs in your answers.

• a) 6.0 x 1020 molecules of carbon dioxide

• b) 7.409 x 1013 molecules of water

• c) 5 x 1046 molecules of methane (CH4)

Bellwork

• You have 10.0 g of aluminum and 73.0 g of gold. Which sample contains more total atoms, the aluminum or gold?

Bellwork

• What is the molecular formula for a compound that is 46.16% carbon, 5.16% hydrogen and 48.68% fluorine if the molar mass of this compound is 156.12 g?

Bellwork

• What is the empirical formula for a compound that contains 17.34% hydrogen and 82.66% carbon?