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7.3

Formula Mass – for any molecule, formula unit, or ion, it is the ____ of the ________ masses of all atoms represented in its formula.

H

2

O for example is

H = 1.008 x 2 = 2.016 amu

O = 15.999 x 1 = 15.999 amu

Total = 18.015 amu

Try to find the mass of

KClO

3

Ca(NO

3

)

2

MgCl

2

H

2

SO

4

PO

4

3-

The mass of 1 mol of a substance in g/mol

H

2

O for example is

H = 1.008 x 2 = 2.016 g/mol

O = 15.999 x 1 = 15.999 g/mol

Total = 18.015 g/mol

The ___ mass is numerically = to the ___ mass

You can convert grams to moles and vice versa using ______ ______

You can also convert atoms to moles and vice versa using ___________ #

What is the mass in grams of 2.50 mol of oxygen gas?

How many moles are in 100 g of H

2

O?

How many moles are in 10 grams of

Carbon?

How many moles are in 3.01 x 10 23 molecules of CH

4

?

How many atoms are in 15 moles of S?

How many molecules are there in the following…

25.0 g H

2

SO

4

125 g Sugar C

6

H

12

O

6

How many grams are in…

6.5 x 10 23 atoms of Cu

5.12 x 10 30 molecules of CH

4

**Percent Composition **– the % by mass of each _________ in a cmpd

To calculate % Comp, determine

_______ mass of entire compound.

Calculate the % of each element by

__________ the mass of each

___________ by the molar mass.

Determine the percent composition of Al and O in

Al

2

O

3

.

Determine the composition of

Al, S, and O in Al

2

(SO

4

)

3

Find the % comp of each element in the following

PbCl

2

Ba(NO

3

)

2

Find the % water in ZnSO4•7H

2

O

Mg(OH)

2 is 54.87% O by mass. How many g of O are in 175 g of the cmpd?

How many moles of O is this?

Complete the section review on page 244 numbers 1-6. This is due at the beginning of class tomorrow!