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Chemistry 20 Mole Conversions

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Chemistry 20Mole Conversions

- A term of measurement
- A counting number
- Similar to saying 1 dozen = 12 things

- Avogadro's Number (NA)
6.02 x 1023 items

A VERY LARGE NUMBER!!!

= 1 mole

- 3.00 moles of little green peas would cover 250 planets the size of Earth 1m deep in green peas
- 1.00 mole of basketballs would fill a bag the size of the Earth

Molar Mass

Mass In Grams

Moles

g/mol

- Molar mass is the mass of one mole in an element or compound
- Atomic mass tells us that the units are grams per mole g/mol
Examples:

Carbon, C = 12.01 g/mol

Phosphorus, P = 30.97 g/mol

What is the Molar Mass of:

Salt, NaCl:

Na = 22.99g/molCl= 35.45g/mol

NaCl = 22.99g/mol + 35.45g/mol = 58.44g/mol

Glucose, C6H12O6:

C6= 6(12.01g/mol)H12 = 12(1.01g/mol) O6 = 6(16.00g/mol)

C6H12O6= 6(12.01g/mol) +12(1.01g/mol) 6(16.00g/mol)

= 180.18 g/mol

Sodium bicarbonate, NaHCO3:

Na= 22.99g/mol H=1.01g/molC=12.01g/mol

O = 3(16.00g/mol)

NaHCO3= 22.99g/mol + 1.01g/mol + 12.01g/mol + 3(16.00g/mol)

= 84.01g/mol

A grade eleven chemistry student has 3.00 g of boron tribromide (BBr3). How many moles of BBr3 is this?

Molar mass of BBr3 = 10.81 + 3(79.90) = 250.51g/mol

3.00g BBr3 x1mole= 0.0120 mole BBr3

250.51g

REMEMBER SIG FIGS!

If I have 50.0g of calcium chlorate (CaClO3)2 how many moles do I have?

Molar Mass (CaClO3)2 =

2(40.08) + 2(35.45) + 6(16.00) = 247.06 g/mol

50.0g (CaClO3)2 x 1 mole = 0.202 mole (CaClO3)2

247.06g

Sig Figs

Determine the mass of the following amount:

6.94 mol barium chloride (BaCl2)

Molar Mass BaCl2 = 137.33 + 2(35.45) = 208.23 g/mol

6.94 molBaCl2 x 208.23 g = 1.45 x 103 g BaCl2

1 mole

Remember only 3 sig figs

Chemistry 20Mole Conversions

Avogadro’s Number

Respective

Particles

Moles

6.02 x 1023 molecules or atoms or formula units

If a chemist is experimenting with 5 700 000 000 atoms of lead how many moles is she dealing with?

Avogadro’s number = 6.02 x 1023 atoms

5 700 000 000 atoms Pb x 1 mole= 9.5 x 10-15mol

6.02 x 1023 atoms

2 sig figs

2 sig figs

How many moles is in 2.97 x 1025 atoms of Vanadium?

2.97 x 1025 atoms of V x 1 mole

6.02 x 1023 atoms

= 49.3 moles of V

Determine the number of molecules in the following:

- 1.01 moles of bismuth
1.01 mol Bi x 6.02 x 1023 atoms

1 mole

= 6.08 x 1023atoms of Bi

b) 2.5 moles of manganese

2.5 molMnx 6.02 x 1023atoms

1 mole

= 1.5 x 1024atoms of Mn

If the students in a chemistry 20 class have

7.66 x 1019 molecules of hydrogen peroxide, H2O2, how many moles do they have?

7.66 x 1019 molecules x1 mole6.02 x 1023 molecules

= 1.27 x 10-4 molecules of H2O2

Chemistry 20Mole Conversions

Litres of Gas at STP

Volume

Moles

22.4 L

Determine the volume, in liters, occupied by 0.030 moles of helium gas at STP.

0.030 moles He(g) x 22.4L = 0.67 L of He(g)

1 mole

REMEMBER UNITS

What is the volume of 0.05 mol of neon gas at STP?

0.05 mol Ne x 22.4L= 1.12L of Ne(g)

1 mole

How many moles of argon atoms are present in 11.2 L of argon gas at STP?

11.2L Ar(g) x 1 mole = 0.5 mole Ar(g)

22.4L

What is the volume of 1.2 moles of water vapor at STP?

1.2 mol H2O(g) x 22.4L= 26.88L of H2O

1 mole

Chemistry 20Mole Conversions

Representative Particles

Volume at STP

x 6.02 x 1023particles

1 mole

X 22.4L

1 mole

x 1 mole

6.02 x 1023 particles

x 1 mole

22.4L

MOLE

x 1mole

molar mass

x molar mass

1mole

Mass

- Write down the question’s the given and the unknown.
- Convert the given unit to number of moles.
- Convert the number of moles found to the unknown unit.
- Make sure the answer has the correct unit and number of sig figs.

Calculate the mass, in grams (g), of the following:

- 3.00L of O2(g)
3.00L of O2(g) x 1 mole x 32.00 g = 4.29 g O2(g)

22.4L 1mole

b) 15 atoms of gold

15 atoms Au(s) x 1 mole x 196.97g = 4.9 x 10-21 g Au

6.02 x 1023 atoms 1 mole

Calculate the number of atoms in 2.0L of SO3 gas.

2.0LSO3(g)x 1 mole x 6.02 x 1023 atoms = 5.3 x 1022 atoms SO3

22.4 L 1 mole

If the students in a Chemistry 20 class have

3.25 x 105 molecules of CO2(g), how many litres do they have?

3.25 x 105molecules of CO2(g) x 1 mole = 5.40 x 10-29 mole

6.02 x 1023molecules

5.40 x 10-29mole CO2 x 22.4L = 1.21 x 10-17 L CO2

1 mole