1. Stoichiometry
SMK Negeri 13 Bandung

2. Stoichiometry Definition :
Stoichiometry is the study of the quantitative relations between amounts of reactants and amounts of products in chemical reactions
It allows us to calculate how much of one chemicals is needed to form another
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3. Unit of matter in chemistry =
Unit in Stoichiometry
Unit of matter in chemistry =
mole
One mole =
6.023X 1023
PARTICLES
6.023X 1023 IS
AVOGADRO’S NUMBER
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4. ATOMIC MASS RELATIVE Mass of neutron = 1 amu
Each atom has a specific mass determined by proton and neutron number
Mass of neutron = 1 amu
Atom with 6 neutron and 6 proton is 12 amu
Mass of proton = 1 amu
Nitrogen 14 = 14 amu
14 amu for nitrogen relative to carbon 12
Carbon-12 is the standard of atomic mass
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5. Molecular Mass Relative
MOLECULE ARRANGED BY ATOMS
MOLECULE’S MASS IS TOTAL AMOUNT OF ATOMIC MASS
H2O consist of 2 H and 1 O
Since Ar of H is 1 amu and Ar of O is 16 amu
Mr of H2O is 18 amu
One molecule of H2O is 18 amu
One mole of H2O
(6.023X 1023molecules) is 18 grams
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6. E.g. 1 mole Li = 6.94 g Li Molar mass
The mass of one mole is called “molar mass”
E.g. 1 mole Li = 6.94 g Li
This is expressed as 6.94 g/mol
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7. Converting between grams and moles
In order to convert from one to the other you must first calculate molar mass g = mol x g/mol mol = g ÷g/mol This can be represented in an “equation triangle ”g = mol X g/mol
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8. Converting grams to moles.
Determine how many moles there are in 5.17 grams of Fe(C5H5)2.
Given
Goal
units match
5.17 g Fe(C5H5)2
= moles Fe(C5H5)2
0.0278
Use the molar mass to convert grams to moles.
Fe(C5H5)2
2 x 5 x =
2 x 5 x =
1 x =

9. Ratios are found within a chemical equation.
Stoichiometry (more working with ratios)
Ratios are found within a chemical equation.
2HCl + Ba(OH)2  2H2O BaCl2 1 1
coefficients give MOLAR RATIOS
2 moles of HCl react with 1 mole of Ba(OH)2 to form 2 moles of H2O and 1 mole of BaCl2

10. gram to gram conversions
Aluminum is an active metal that when placed in hydrochloric acid produces hydrogen gas and aluminum chloride. How many grams of aluminum chloride can be produced when 3.45 grams of aluminum are reacted with an excess of hydrochloric acid?
Al(s) HCl(aq)  AlCl3(aq) H2(g)
3.45 g
? grams
Units match
3.45 g Al
= g AlCl3
17.0
Let’s work the problem.
We must always convert to moles.
Now use the molar ratio.
Now use the molar mass to convert to grams.

11. Molarity
Molarity is a term used to express concentration. The units of molarity are moles per liter (It is abbreviated as a capital M)
When working problems, it is a good idea to change M into its units.

12. Solutions
A solution is prepared by dissolving 3.73 grams of AlCl3 in water to form mL solution. A 10.0 mL portion of the solution is then used to prepare mL of solution. Determine the molarity of the final solution.
What type of problem(s) is this?
Molarity followed by dilution.

13. Solutions 1st: 3.73 g = mol 0.140 L 200.0 x 10-3 L M1V1 = M2V2 2nd:
A solution is prepared by dissolving 3.73 grams of AlCl3 in water to form mL solution. A 10.0 mL portion of the solution is then used to prepare mL of solution. Determine the molarity of the final solution.
1st:
3.73 g
= mol L
0.140
200.0 x 10-3 L
molar mass of AlCl3
dilution formula
M1V1 = M2V2
2nd:
(0.140 M)(10.0 mL) = (? M)(100.0 mL)
final concentration
M = M2

14. Converting grams to grams
We cannot directly convert from grams of one compound to grams of another.
we have to go through moles.•
Many stoichiometry problems follow a pattern: grams(x) ↔moles(x) ↔moles(y) ↔grams(y)•
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