Introduction to Quantities in Chemical Formulas 4.1: Proportions in Compounds Compare carbon dioxide...
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Transcript of Introduction to Quantities in Chemical Formulas 4.1: Proportions in Compounds Compare carbon dioxide...
Introduction to Quantities in Chemical Formulas4.1: Proportions in CompoundsCompare carbon dioxide and carbon monoxide
Carbon dioxide: Chemical formula :
Physical Properties:
When does it form: when there is a large amount of O2 availableAffect to humans: plants use it to produce O2, which we breatheOxygen Ratio:
Chemical formula :
Physical Properties:
When does it form: when there is a small amount of O2 availableAffect to humans: -binds to hemoglobin, -not able to transport oxygen to the body -tissue damage and organ failure
Oxygen Ratio:
Carbon monoxide:
CO2
-Colourless-Odourless
1: 2 (1 carbon atom for every 2 oxygen atoms)
1: 1 (1 carbon atom for every 1 oxygen atom)
CO
-Colourless-Odourless
So to analyze chemical reactions quantitatively….
Stoichiometry: the study of the relationships between the quantities of reactants and products involved in chemical reactions
Law of Definite Proportions: the proportions of elements in a specific compound, are always the same, no matter how the compound is made.
-The properties of a substance will depend on:1) the elements in the compound2) the quantity of each element in the compound
Ex. 2 : O2 vs. O3
Law of Definite Proportions
Ex. 1 : Sort the following atoms and determine the compound's chemical formula.
OO O
H
HH
H
H H
HH
HHH
HH
H
H
H
H H
HH
HH
HO O O
O O OO
H
OO
Oxygen Box Hydrogen Box
# of oxygens =
# of hydrogens = ratio: :
The compound's chemical formula is: _______________
Use the law of definitive proportions to determine the unknown masses.
Exp 1 2 g + 71 g 73 g
Exp 2 6 g + 213 g 219 g
Exp 3 ? g + 17.75 g 18.25 g
Exp 4 150 g +
? g ? g
hydrogen + chlorine
?
4.2 Relative Atomic Mass
-Relative atomic mass helps us to understand how the mass numbers on the periodic table were found
-When John Dalton came up with the Billiard Ball model,he also determined a way to express the mass of atoms -What was the billiard ball model and what did it tell
us about the mass of atoms?
-Using this information and the law of definite proportions, Dalton was able to express the masses of atoms RELATIVE TO EACH OTHER!
-For example, if we obtain the following results from the reaction of calcium and oxygen to form calcium oxide:
calcium + oxygen calcium oxide 40g 16g
56g
-Now, Dalton used hydrogen first because it was the lightest element and gave it a mass of 1.
-he compared all the other element to this value
For ex. : when Dalton looked at water, he saw thta 1 g of hydrogen combined with 8 g oxygen -so he gave oxygen a mass of 8-this was a mistake since 2 atoms of oxygen combines with one atom of hydrogen -So oxygen must have a relative atomic mass of 16
So what do we mean by relative atomic mass
Relative atomic mass: mass of an element that would react with a fixed mass of a standard element
-we are currently using carbon -12 as our standard element
Why?
Units, Units, Units!-Remember IUPAC and SI units, the proper units for the mass of an atom are atomic mass units or "u"Atomic mass unit: 1 u is equal to 1/12th the mass of a carbon-12 atom
and just to put this into perspective:
1 u = 1.66´ 10-27 kg (thats really tiny!)
Ex.1 - What is the mass of 1 carbon-12 atom? Use atomic mass units.
Ex.2 - If a titanium atoms weighs 4 times a carbon-12 atom, calculate the atomic mass of titanium in u.
Bonus: Express this in kg
Homework
Pg.162 #1Pg.164 # 1,3,4