convert the following:1. 0.30 m = ______dm2. 5days =________minutes3. 4000 dm3 = _______ m3

4. 1.2 x 106 – 2 x 105 = _____5. Find the gfw of NaCl6. ACT-prep question:

1. Many physicists believe the elementary particles of the atom are composed of still more elementary particles called the:a) photonsb) quarksc) neutronsd) electrons

Quiz: Factor Label Method

0.30 m (10 dm) (1 m)

3

5 days (24hours) (60 min) (1 day)(1 hour)

7.2 x 103

4000dm3 (13 m3)

(103 dm3)

4

February 24, 2005

1.2 x 106 – 0.2 x 106

Na = 23 amu, Cl = 35 amu1(23) + 1(35) = 58 amuor 58 g/mole

1.0 x 106

Gram Formula Weight of HCl

35.45 amu

1.008 amu

35.45 + 1.008 = 36.46 amu or 36.46 g/mole

Gram Formula Weight of NH3

14.01 amu

1.008 amu

14.01 + 3(1.008) = 17.03 amu or 17.03 g/mole

NH H

H

Gram Formula Weight of (NH4)2O

NH4+NH4+NH4+NH4+ O2-

N = 14 amuH = 1 amuO = 16 amu

2N = 2(14 amu)2x4H = 8(1 amu)1O = 1(16 amu)

28 amu 8 amu16 amu52 amuor 52 g/mole

Quiz: Find the gfw for the following compounds…

1. CaCl

2. Al2S3

3. Ca3(PO4)2

1. 40 + 35 = 75 g/mole

2. 2(27) + 3(32) =54 + 96 =

150 g/mole

3. 3(40) + 2(31) + 8(16)

= 120 + 62 + 128

= 310 g/mole

Using the GFW (gram formula weight) for calculations

• The gram formula weight (gfw) is a conversion factor, just like 100 cm = 1 m

or 1 Avogadro number of particles = 1 mole.

Use the same procedure as before: Write the known, then write the appropriate conversion factor. Underline the important facts.:

Example: How many moles of NaCl are in 4.00 grams of NaCl?

Na = 23.0 amuCl = 35.5 amu58.5 g/mole

4.00 g NaCl

58.5 g NaCl

1 mole NaCl

0.0684 mole NaCl

Find the number of moles in 0.020 grams of the following:

• CaCO3

• Ca3(PO4)2

Ca = 40C = 123O = 3(16) = 48 100 g/mole

Known:0.020 grams CaCO3

100 g/mole

Find: moles CaCO3

(0.020 grams CaCO3) (1mole CaCO3)( 100 g CaCO3)

= 2.0 x 10-4 moles CaCO3

3Ca = 3(40) = 1202P = 2(32) = 648O = 8(16) = 128 312 g/mole

Known:0.020 moles Ca3(PO4)2

312 g/mole

Find: grams Ca3(PO4)2

(0.020 grams Ca3(PO4)2) (mole Ca3(PO4)2)( 312 g Ca3(PO4)2)

= 6.4 x 10-5 moles Ca3(PO4)2 or 0.000064 moles Ca3(PO4)2

Another example of using the GFW for calculations

• Use the same procedure as before: Write and underline the known, then write the appropriate conversion factor:

Example: How many grams of NaCl are in 0.2 moles of NaCl?

Na = 23.0 amuCl = 35.5 amu58.5 g/mole

0.2 mole NaCl 58.5 g NaCl

1 mole NaCl

11.7 g NaCl

Find the number of grams in 0.020 moles of the following:

• CaCO3

• Ca3(PO4)2

Ca = 40C = 123O = 3(16) = 48 100 g/mole

Known:0.020 moles CaCO3

100 g/mole

Find: grams CaCO3

(0.020 moles CaCO3) (100g CaCO3)( mole CaCO3)

= 2.0 g CaCO3

3Ca = 3(40) = 1202P = 2(32) = 648O = 8(16) = 128 312 g/mole

Known:0.020 moles Ca3(PO4)2

312 g/mole

Find: grams Ca3(PO4)2

(0.020 moles Ca3(PO4)2) (312g Ca3(PO4)2)( mole Ca3(PO4)2)

= 6.24 g Ca3(PO4)2 Rounded to 6.2 g Ca3(PO4)2