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Chapter 17
Atomic vs. Molecular Weight
Atomic weight on periodic table is average of natural abundance of isotopes Atomic mass is the number of nucleons in a particular atom—specified by isotope Molecular mass is the mass of one mole of molecules One atomic mass number of grams 6.0221367x10 23 molecules
Calculate Molecular Mass
O atomic weight 15.9996 (round to 16 for this class) O-16 atomic mass 16 u Molecular oxygen O atomic mass 32 uMolecular oxygen O 2 atomic mass 32 u Molecular O 2 molecular mass 32 g/mole
CO 2 molecular mass
C=12 g/mole, O 2 =32 g/mole CO 2 =12+32=44 g/mole
Na 2 CO 3 molecular mass
Na = 23 g/mole C = 12 g/mole O = 16 g/mole 2 N 2 Na, 3 O, so multiply 3 O lti l 2(23) + 12 + 3(16) = 106 g/mole
Write these down
C = 12
H = 1
O = 16
NN = 14 14
K = 39
Cl = 35. Use for some questions
2 KClO 3 2 KCl + 3 O 2
How many grams of oxygen can be produced from 122.45 g of KClO 3?
- First find molecular masses of substances
- Convert 122.45 g of KClO 3 to moles 3 3. Find molar ratios from balanced equationFind molar ratios from balanced equation
- Calculate moles of O 2
- Convert that to grams of O (^2)
2 KClO 3 2 KCl + 3 O 2
How many grams of oxygen can be produced from 122.45 g of KClO 3?
- 32.00 g
- 48.00 g 3 3. 61 22 g61.22 g
- 122.45 g
1 2 3 4
0% 0% 0% 0%
1 CH 4 + 2 O 2 2 H 2 O + 1 CO 2
How many grams of water are produced from 1. moles of methane?
- 11.25 grams
- 22.5 grams 3 3. 45 grams45 grams
- 90 grams
1 2 3 4
0% 0% 0% 0%
Moles calculated from Grams
176 g of CO 2 = Number of moles? Molar mass of CO 2 = 44 If you multiply, 176 g x 44 gl^ results in units of g^
2
mole
g
176 g x 44 results in units of you get a unit mess UNITS alert you that you made an error KEEP UNITS WITH NUMBERS!!
mole (^) mole
Mass to moles relationship To convert between grams and moles
Find molar mass Divide grams by molar mass
Problem
H 2 S O 2 SO 2 H 2 O
- 32 grams SO (^2)
- How many grams OHow many grams O 2 2 used?used?
Problem
Balance first
H (^) 2 S O 2 SO 2 H 2 O
2 H (^) 2 S 3 O 2 2 SO 2 2 H 2 O
- 32 grams SO (^2)
- How many grams O 2 used?
Then determine molar ratios 2 SO 2 to 3 O 2
2 H (^) 2 S 3 O 2 2 SO 2 2 H 2 O
Problem
Find molar masses
2 H (^) 2 S 3 O 2 2 SO 2 2 H 2 O
- 32 grams SO (^2)
- How many grams O 2 used?
SO 2 = 32 + 32 = 64 g/mol SO 2
O 2 = (2x1) +16 = 32 g/mol O 2
H 2 O = (2x1) +16 = 18 g/mol H 2 O
H 2 S = (2x1) +32 = 34 g/mol H 2 S
Problem
2 H (^) 2 S 3 O 2 2 SO 2 2 H 2 O
- 32 g SO 2 needs how many grams O 2?
- How many moles is 32 g SO 2?
- 32 grams SO (^2)
- How many grams O 2 used?
2 0.^5 SO 2
64 g
32 gSO moles
mole
Problem
2 H (^) 2 S 3 O 2 2 SO 2 2 H 2 O
- How many moles O 2 is needed?
- 0.5 moles SO 2 in 2:3 ratio with O 2
- 32 grams SO (^2)
- How many grams O 2 used?
2 0.^5 SO 2
64 g
32 gSO moles
mole
Set up
proportion
? O
with the unknown on top (the O 2 )
- 32 grams SO (^2)
- How many grams O 2 used?
? g O 2
Problem 6
Is it balanced? Molar ratio 1:1: 4 grams oxygen Grams carbon consumed?
C O 2 CO 2
Grams carbon dioxide produced?
Problem 6
Molar ratio 1:1: 4 grams oxygen 1 mole O 2 = 32 g
C O 2 CO 2
2 0.^1252 32
1 4 molesO g
mole g O
Problem 6
Molar ratio 1:1:
0.125 moles O 2 in 1:1 ratio
C O 2 CO 2
0.125 moles C 0.125 moles CO (^2)
Problem 6
0.125 moles C Grams carbon consumed?
g C
g
moles C 15
C O 2 CO 2
g C
mole
moles C 1. 5
2 5.^52
0. 125 mole gCO
mole
g
CO
Reaction Speed
Collision of molecules required for it to occur Increase concentration Increase temperatureIncrease temperature Catalyst can facilitate reaction
Chlorine catalyst
