Moles, Atoms, Molecules 10C



Chem I Ch 10 Notes/ Chem I H chapter 11 notes

10A

The atomic mass is found by checking the periodic table.

The atomic mass is the number of grams of an element that is numerically equal to the mass of an atomic mass unit. atomic mass C = 12.0 g

The atomic mass is the mass of one mole of atoms.

Mole – quantity such that there are as many atoms as in 12 g of carbon

The mass of a mole of NaCl is the molar mass.

1 atom 1 mole 1 molecule 1 mole

C 12.0 u 12.0 g Cl2 2Cl 2 X 35.5u = 71.0u 71.0 g

Fe 55.8 u 55.8 g H2O 2H 2 X 1.0u = 2.0u

Cu 63.5 u 63.5 g 1O 1 X 16.0u = 16.0u 18.0 g

18.0u

C3H6 3C 3 X 12.0u=36.0u

6H 6 X 1.0u= 6.0u 42.0 g

42.0u

1 formula unit 1 mole

2Al, 2 X 27.0u = 54.0u

Al2(SO4)3 3S, 3 X 32.1u = 96.3u 342.3 g

12 O, 12 X 16.0u = 192.0u

342.3u

Notes Converting grams to moles 10B

To convert first write what you are given.

Then “times sign draw a line”.

Place what you want above the line and the given below the line.

“mol” always has a coefficient of 1.

Where you see “g”, go to the periodic table to find the value.

Ex 1 How many grams are in 6.50 moles of H2SO4?

[pic] 2H 2 X 1.0 = 2.0g

1S 1 X 32.1 = 32.1g

4 O 4 X 16.0 = 64.0g

98.1g

Ex 2 What is the mass in grams of 5.90 mol C8H18? 8C 8 X 12.0 = 96.0g

[pic] 18H 18 X 1.0 = 18.0g

[pic] 114.0g

Ex 3 What is the number of moles in 432 g Ba(NO3)2?

1 Ba 1 X 137.3 = 137.3g

2 N 2 X 14.0 = 28.0g

6 O 6 X 16.0 = 96.0g

261.3g

[pic][pic]

Moles, Atoms, Molecules 10C

Representative particle - atom, molecule, or formula unit.

A mole of a substance contains

6.02 X 1023 representative particles

Avogadro’s number = 6.02 X 1023

Mole – SI unit used to measure number of representative

particles in a substance

A dozen is to eggs as mole is to atoms.

Conversion questions to answer – What’s the unknown

What is given

How many times signs

Molecules will always have 1 or 6.02 X 1023

EX 1

How many moles of magnesium is 1.25 X 1023 atoms of magnesium?

[pic]

EX 2

How many atoms are in 2.12 mol of C3H8 (propane)?

[pic]

Percent Composition 10D

[pic]

[pic]

Ex 1

Find the % composition of C3H8.

3C 3 X 12.0 = 36.0g

8H 8 X 1.0 = 8.0g

44.0g

[pic]

[pic]

Ex 2

What is the percentage of nitrogen in NH3?

1N 1 X 14.0 = 14.0g

3H 3 X 1.0 = 3.0g

17.0g

[pic]

Empirical Formulas 10E

Empirical formula – lowest whole-number ratio of the elements

in a compound (divide by – Greatest Common Factor)

CNH4 not C2N2H8

Empirical Formula Calculations

Change the given information to moles for each

element.

Divide each mole answer by the smallest

number of moles.

If the answers from step 2 are not whole numbers

then divide by the smallest decimal part.

Write the formula with the mole ratio as subscripts.

EX 1 Find the empirical formula. A compound contains

9.31g of Ag and 0.69g of O.

[pic]

[pic] Ag2O

EX 2 A compound contains 25.9% N and 74.1% O.

Find the empirical formula.

[pic] 1(.5 = 2

[pic] 2.50 ( .5 = 5

N2O5

Molecular Formulas 10F

Molecular formula – empirical formula or its multiple

Several compounds can have the same empirical formula but different molecular formulas.

Convert molecular ( empirical

Divide subscripts by greatest common factor

empirical ( molecular

multiply subscripts by [pic]

EX 1

The empirical formula is CH4N and the molar mass is 60.0 g. Find the molecular formula.

C 1 X 12.0 = 12.0g

4H 4 X 1.0 = 4.0g [pic] C2H8N2

N 1 X 14.0 = 14.0g

30.0g

EX 2

Find the molecular formula of C4H6O if the molar mass is 280.0g.

4C 1 X 12.0 = 48.0g

6H 4 X 1.0 = 6.0g [pic] C16H24O4

O 1 X 14.0 = 16.0g

70.0g

Name______________________Pd._____ Date_________ Chem I H Chapter 11 Notes/ Chem I Chapter 10 Notes

10A

The atomic mass is found by checking the __________ ______.

The _____________ ________ is the number of grams of an element that is numerically equal to the mass of an atomic mass unit. (atomic mass C = 12.0 g)

The atomic mass is the mass of one ____________ of atoms.

Mole – quantity such that there are as many atoms as in 12 g of carbon

The mass of a mole of NaCl is the ______________ ________.

1 atom 1 mole 1 molecule 1 mole

C 12.0 u 12.0 _ Cl2 2Cl 2 X 35.5u = 71.0 _

Fe 55.8 u 55.8 _ H2O 2H 2 X 1.0u =

Cu 63.5 u 63.5 _ 1 O 1 X 16.0u =

C3H6 3C 3 X

6H 6 x

1 formula unit 1 mole

Al________________________

Al2(SO4)3 S________________________

O ________________________

Ch 10 Notes Converting grams to moles 10B

To convert first write what you are ______________________.

Then “times sign__________________________________”.

Place what you want above the line and the given below the line.

“mol” always has a coefficient of __________.

Where you see “g”, _______ to the periodic table to find the value.

Ex 1 How many grams are in 6.50 moles of H2SO4? Show all work

2H ____________________

1S ____________________

________________________ 4 O ____________________

____________________

Ex 2 What is the mass in grams of 5.90 mol C8H18? 8C__________

____________

[pic]______________________________ g

Ex 3 What is the number of moles in 432 g Ba(NO3)2?

Ba

N

O

_____________________________________

Moles, Atoms, Molecules 10C

Representative particle - atom, molecule, or _________ _____

A mole of a substance contains

____________________ representative particles

Avogadro’s number = ______________________

_________– SI unit used to measure number of representative

particles in a substance

A dozen is to eggs as mole is to atoms.

Conversion questions to answer – What’s the ______________

What is given

How many times _________

Molecules will always have 1 or ___________________

EX 1

How many moles of magnesium is 1.25 X 1023 atoms of magnesium?

___________________________________________

EX 2

How many atoms are in 2.12 mol of C3H8 (propane)?

___________________________________________

Percent Composition 10D

[pic]

[pic]

Ex 1

Find the % composition of C3H8.

3C ______________

8H ______________

_____

_____________________________

_____________________________

Ex 2

What is the percentage of nitrogen in NH3?

1N ______________

3H ______________

_____

_____________________________

Empirical Formulas 10E

Empirical formula – lowest __________________

ratio of the elements in a compound

(divide by – Greatest Common Factor)

i.e. CNH4 not C2N2H8

Empirical Formula Calculations

Change the given information to __________ for each

element.

Divide each mole answer by the _________________

number of moles.

If the answers from step 2 are not whole numbers

then divide by the smallest decimal part.

Write the formula with the mole ratio as ___________.

EX 1 Find the empirical formula. A compound contains

9.31g of Ag and 0.69g of O.

9.31 g Ag X

0.69 g O X

Which answer is the smallest number?____________________

[pic]

[pic] ______________________

EX 2 A compound contains 25.9% N and 74.1% O.

Find the empirical formula. (Hint: change % to grams)

Molecular Formulas 10F

Molecular formula – empirical formula or its ______________

Several compounds can have the same _____________ _____

but different molecular formulas.

Convert molecular ( empirical

Divide subscripts by ______________ __________ _________

empirical ( molecular

multiply subscripts by ___________________

EX 1

The empirical formula is CH4N and the molar mass is 60.0 g. Find the molecular formula.

C 1 X 12.0 = 12.0g

4H 4 X 1.0 = 4.0g

N 1 X 14.0 = 14.0g __________________

30.0g

EX 2

Find the molecular formula of C4H6O if the molar mass is 280.0g.

4C 1 X 12.0 = 48.0g

6H 4 X 1.0 = 6.0g

O 1 X 14.0 = 16.0g ____________________

70.0g

Ch 10 Test Reference

Percent Composition [pic]

Empirical Formula Calculations

Change the given information to moles for each

element.

Divide each mole answer by the smallest

number of moles.

If the answers from step 2 are not whole numbers

then divide by the smallest decimal part.

Write the formula with the mole ratio as subscripts.

Convert molecular ( empirical

Divide subscripts by greatest common factor

Convert empirical ( molecular

multiply subscripts by [pic]

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