Name: Unit 8- The Mole 8 Student...1. How many atoms are in 2.5 moles of silver? 2. What is the molar mass of calcium phosphate? Day 3 1. What is the empirical formula for a compound

Unit 8: The Mole Page 1

Name: _________________________________

Unit 8- The Mole

Day Page # Description IC/HW Due Date Completed

All 2 Warm-up IC

1 3 – 4 Notes on the Mole IC

1 5 – 7 The Mole IC

1 8 – 9 Chemical Quantities HW

2 10 Percent Composition Notes IC X

2 Gum Lab IC/HW

2 11 – 12 Percent Composition HW

2 13

Empirical and Molecular Formula Notes

IC

2 14

Empirical and Molecular Formulas Practice

HW

3 15 Hydrates Notes IC

3 16 – 17 Hydrates HW

4 Water in a Hydrate IC/HW

4 21 – 22 Unit 8 Test Review HW

5 X Unit 8 Test In class on 2/13 and 2/14


Warm-up

Day 1

1. If you are making 113 dozen mini cupcakes, and each batch makes 60 mini cupcakes,

how many batches will you need to make?

Day 2

1. How many atoms are in 2.5 moles of silver?

2. What is the molar mass of calcium phosphate?

Day 3

1. What is the empirical formula for a compound which contains 15.77 % aluminum, 28.11

% sulfur, and 56.12 % oxygen?

Day 4

1. Magnesium chloride from a hydrated salt. When a sample of magnesium chloride is

analyzed, it is found to contain 53.20 % water. Determine the hydrate formed.

Day 5

1. How many moles are in 1.20*1025 atoms of iron?


Calculating the Molar Mass of a Compound

The mass on the periodic table is known as the Molar Mass. It has units of g/mol.

1. Write the formula

2. Calculate the mass by adding up the masses of each element in the

compound.

3. Make the unit g/mol.

Example: Calculate the mass of one mole of calcium chloride.

o Write the formula

o Calculate the mass

o Change the unit

Barium nitrate

Xenon tetrachloride

Sodium Phosphate

Carbon dioxide

Potassium sulfide


Notes on the Mole

A mole is a counting number. One mole is a specific number of atoms,

molecules or formula units. Avogadro’s number is ___________________.

Now we can relate the atomic mass unit to the gram. 1 atom of carbon 12

has a mass of 12.01 amu. 6.02*1023 atoms of carbon-12 have a mass of

12.01 g. 1 mole of carbon atoms have a mass of 12.01 g.

A formula unit is the lowest whole number ratio of atoms or ions in a

compound.

If you had 1.0 mol of quarters and stacked them up, how many times could

you get to the moon and back? (1 quarter = 2.0 mm thick; the distance to

the moon is 382500 km)

Calculate the number of formula units present in 3.45 moles of barium

nitrate.

Calculate the number of molecules in 19.3 moles of ammonia (NH3).

Calculate the mass of 7.89*10-20 atoms of oxygen.


The Mole

1. A mole is defined as the amount of substance that contains as many particles

as there are atoms in

2. Avogadro’s number is equal to

3. The molar mass of a given substance is defined as

4. Recall that one atomic mass unit (amu) is defined as a relative unit used to

express the masses of atoms (or molecules).

4. Perform the following conversions, using dimensional analysis.

Mass Molar mass Moles 6.02 x 1023 Particles

(atoms, molecules) PT to find molar mass Avagadro’s number

a) Calculate the mass of 1.73 mol of zirconium (Zr).

1.73 mole Zr x g Zr = g Zr

1 mole Zr

b) What is the mass in grams of 3.50 moles or the element copper?


c) Calculate the number of moles of zinc (Zn) in a sample that weighs 143 grams.

d) A chemist produced 11.9 grams of AL. How many moles of aluminum were

produced?

e) Calculate the number of atoms of in a sample of calcium (Ca) with a mass of

6.14 grams.

6.14 g Ca x 1 mole Ca x atoms Ca =

atoms Ca g Ca 1 mole Ca

f) Determine the number of atoms in 1.50 grams of carbon.

g) Calculate the mass of a sample of platinum (Pt) that contains 2.15 x 1024

atoms.


Chemical Quantities

Show ALL work for the following problems!!

1. 45.3 g of Nitrogen is how many moles?

2. How many molecules are in 112.5g of dinitrogen tetroxide.

3. What is the mass of 6.70 x 1024 formula units of Lead (IV) Oxide?

4. How many molecules are in 56.2g of carbon dioxide?

5. How many molecules are in 36.5 g of water?


6. What is the mass of 4.67 x 1023 molecules of xenon pentafluoride?

7. How many atoms of chlorine are in a 56.2 g sample?

8. How many formula units are in 4.56 g of Zinc hydroxide?

9. How many atoms of fluorine are in a 56.8 g sample?

10. What is the mass of 8.96 x 1022 molecules of carbon tetrafluoride.


PERCENT COMPOSITION NOTES

Percent composition refers to what percent of the compound is made up of each

element. To calculate the percent composition, divide the mass of the element

by the molar mass of the compound. If there is more than one atom of an

element, you must multiply the molar mass by the number of moles. Let’s

calculate the percent composition of Oxygen and Hydrogen in water.

Molar mass of oxygen: 16.00 g

Molar mass of hydrogen: 1.008 g

Molar mass of water: 18.016 g

The percent composition of oxygen is:

If the two percents add up to 100 %, a good indication that you did the problem

correctly




Empirical and Molecular Formula Notes

Empirical Formulas- Indicate the ______________ of atoms present in a compound.

Molecular Formulas- Indicate the _________________ of atoms present in a compound.

Ex: Glucose

Steps to calculate an empirical formula:

1. Start with the mass of each element given in the problem. (If percents are given, assume the sample has 100 g, and change the percentage unit to grams.)

2. Convert to moles. 3. Divide each by the smallest number of moles to get the ratio. (If necessary, multiply

to get whole numbers.) 4. Answers in #3 become subscripts.

Ascorbic Acid (vitamin C) is 40.92% Carbon, 4.58% Hydrogen and 54.50% Oxygen by

mass. Calculate the empirical formula for Ascorbic Acid.

A 5.325 g sample of methyl benzoate, a compound used in the manufacture of

perfumes, is found to contain 3.758 g of carbon, 0.316 g of hydrogen and 1.251 g of

oxygen. What is the empirical formula of methyl benzoate.

Steps to calculate a molecular formula:

1. Calculate the empirical formula. 2. Calculate the molar mass of the empirical formula. 3. Divide the mass of the molecular formula (given) by the mass of the empirical

formula. 4. Multiply the subscripts in the empirical formula by the answer in step 3.

Mesitylene, a hydrocarbon that occurs in crude oil, is 89.92% carbon. The molar mass of

this compound is 121 g/mol. Calculate the empirical and molecular formulas of this

substance.


Empirical and Molecular Formulas Practice

1. What is the empirical formula of a compound that is 25.9% nitrogen and 74.1%

oxygen?

2. What is the empirical formula of a compound that is 79.9% carbon and 20.1%

hydrogen?

3. What is the empirical formula of a compound that is 17.6% Na, 39.7% Cr and

42.7% O?

4. You find that 7.36g of a compound contains 6.93g of oxygen while the rest is

hydrogen. If you know the molar mass of the compound is 34.0g/mol what is the

molecular formula?

5. What is the molecular formula of a compound that is 54.5% carbon, 13.6%

hydrogen and 31.8% nitrogen? Its molar mass is 88g/mol.

6. What is the molecular formula of a compound that is 40.0%C, 53.4%O and

6.6%H. Its molar mass is 120 g/mol.


Hydrates Notes

A hydrate is __________ with a specific number of ___________ molecules

around it.

o To name a hydrate, name the salt, then use the covalent pre-fixes to

indicate the number of waters. Follow the pre-fix with the word

“hydrate.”

EX: MgSO4∙7H2O (Magnesium sulfate heptahydrate)

o CuCl2 6H2O

An Anhydrous compound contains ______________, but has the capability

to ______________ water.

Remember the formula for percent error!

The percent of calcium in calcium chloride was experimentally determined

to be 32.1%. Calculate the % error.


Hydrates

1. Name the following hydrates.

a. NaC2H3O2 3H2O

b. Ba(OH)2 8H2O

c. CoCl2 6H2O

2. Write the formula for the following hyrdrates.

a. Calcium chloride dihyrdrate

b. Ammonium oxalate monohydrate

c. Iron (III) Phosphate hexahydrate

3. Calculate the % water in each of the following hydrates.

a. Sodium carbonate decahydrate

b. Barium hydroxide octahydrate.

c. Strontium chloride hexahdrate.


4. A hydrated sodium tetraborate is commonly called Borax. Chemical analysis indicates that

this hydrate is 52.8% sodium tetraborate [Na2B4O7] and 47.2% water. Determine the formula

and name the hydrate.

5. A 1.628 g sample of a hydrate of magnesium iodide is heated until its mass is reduced to

1.072 g and all water has been removed. What is the formula of the hydrate?

6. The data table below shows data from an experiment to determine the formulas of hydrated

barium chloride. Determine the formula for the hydrate and the name of the hydrate.

Mass of empty crucible 21.30 g

Mass of hydrate and crucible 31.35 g

Initial mass of hydrate

Mass after heating 29.87 g

Mass of anhydrate


Unit 8 Test Review

1. The molecular formula of allicin, the compound responsible for the

characteristic smell of garlic, is C6H10OS2.

(a) What is the molar mass of allicin?

(b) How many moles of allicin are present in 5.00 mg of this substance?

(c) How many molecules of allicin are present in 5.00 mg of this substance?

(d) How many sulfur atoms are present in 5.00 mg of allicin?

2. A sample of glucose, C6H12O6, contains 5.77 x 1020 atoms of carbon.

(a) How many atoms of hydrogen does the sample contain?

(b) How many molecules of glucose does the sample contain?

(c) What is the mass of the sample?


3. Calculate the percent composition of Oxygen in the following compounds:

calcium carbonate, lead (II) hydroxide, acetic acid, and magnesium phosphate.

4. Adrenaline, a hormone secreted into the bloodstream in times of danger or

stress is 59.0% carbon, 7.1% Hydrogen, 26.2% oxygen and 7.7% nitrogen. The

molar mass of adrenaline is 180 g/mol. Calculate the molecular formula of

adrenaline.

5. The characteristic odor of pineapple is due to ethyl butyrate, a compound

containing carbon, hydrogen and oxygen. Combustion of 2.78 mg of ethyl

butyrate produces 6.32 mg of CO2 and 2.58 mg of water. The molar mass of ethyl

butyrate is 116.16 g/mol. Determine the molecular formula of ethyl butyrate.

6. Epsom salts, a substance used as a strong laxative by veterinarians, is a hydrate

of magnesium sulfate. When 5.061 g of the hydrate is heated all the water of

hydration is lost leaving 2.472 g of the anhydrate. Determine the formula of this

hydrate and name the hydrate.

Documents

Name: Unit 8- The Mole 8 Student...1. How many atoms are in 2.5 moles of silver? 2. What is the molar mass of calcium phosphate? Day 3 1. What is the empirical formula for a compound