Embed Size (px)
Citation preview
Warm-Up List as many
counting terms as you can.
A counting term is a word that represents a specific number
Ex: Pair = 2 Dozen = 12 Score = 20 Gross = 144 Mole = 6.02 x 1023
CH 7 The Mole and Chemical Compounds
Avagadro’s NumberThe moleMole ConversionsPercent CompositionEmpirical Formula
The mole – like a dozen only bigger
Equal to the number of atoms in 12.0g of carbon-12.
1 Mole = 6.02 x 1023
particles
Also known as:Avagadro’s Number
After Italian physicist Amadeo Avogadro
Chemistry particles
An atom Na, Li, He
A molecule O2 , H2O , CCl4
A formula unit (this is what you call a “molecule” of an ionic substance)
NaCl, MgO, H2SO4
Conversions
A conversion factor is a form of the number 1. Multiplying by it only changes the units.
Multiply using the conversion factor with the units you WANT on the top.
How many eggs in 5 dozen?
How many score in 90 years?
How many atoms are there in 2.0 mol of sodium?
How many atoms in 3.5 mol of sodium?
How many molecules are there in 2.5 mol of sulfur dioxide?
How many atoms are there in 2.5 mol of sulfur dioxide?
Label each of the followingatom, molecule, or formula unit (F.U.), or ion
Sodium Metal: Na Oxygen gas: O2
Water: H2O Sodium Chloride: NaCl Iron (III): Fe3+
Phosphorus Trichloride: PCl3 Methane: CH4
Solve on Whiteboard, show work
How many atoms are there in 0.02mol of Iron?
How many atoms are there in 0.02mol of Water?
How many moles are there in 9.03x 1024 molecules of water?
How many moles are there in 9.03x 1024 molecules of water?
“molecular weight” “molar mass”
The mass of one mole of an element or compound.
Determine the mass using the atomic mass from the periodic table. (numerically equal to atomic mass)
atomic weight molar mass
Sodium 22.99 amu 22.99 g
Magnesium
24.30 amu g
How to calculate molar mass1. Use the atomic mass
from the periodic table.
2. Add up the atomic masses for each element in the compound.
NaCl = 22.99g + 35.45g
58.44 grams/mole
Ex. H2O2 Hydrogens x 1.0g+1 Oxygen x 16.0g
18.0 grams/ mole
Find the molar mass of the following compounds CO2
LiF
Na2S
HCl
KClO
Warm-Up What is the molar mass of Sulfur Trioxide
S = 1 x 32.1O = 3 x 16.0
80.1 g/mol
Find the molar mass of
Acetic Acid HC2H3O2
What is the mass of 2 moles of acetic acid?
Writing/abbrevieating:Mole
Mole mol (don’t read this as “molecule”)
n
2.0 moles of Carbon = 24.02g2.0 mol Carbon = 24.02g2.0 n Carbon = 24.02g
Determine the molar mass
NH3
What is the mass of 3 moles of NH3
14+1+1+1 = 17 g/mol
3mol x 17 g/mol = 51g
Determine the mass of 1.75mol Uranium 0.7mol SF6
Determine the mass of
1. 0.720 mol Be2. 2.40 mol N2
3. 4.52x10-3 mol C20H42
4. 5.08 n Calcium Nitrate
Find the number of moles in1. 5.00g of Hydrogen gas (H2)2. 11.0 g of methane (CH4)3. 333g of Tin (II) Fluoride
Converting #Particles to Mass
1. Divide the number of particles by Avagadro’s # to get moles.
2. Multiply the #moles by molar mass to get grams
Find the mass of 2.44 x 1024 atoms of Carbon.
Calculate the mass slates path: Particles Moles Mass
5.3 x 1023 atoms of Molybdenum (Mo)
1.299 x 1026 ions of Nitrate (NO3-)
6.12 x 1014 formula units of Rhenium Oxide (ReO2)
Calculate the # of Particles slates path: Mass Mole Particles
How many atoms in 54.3g of Cobalt (Co) ?
How many molecules in 245g of Oxygen gas (O2)?
How many molecules in 0.0923g Hydrgen Fluoride gas (HF)?
Molar Volume of a gas
Molar volume of a gas
The volume of 1 mole of a gas (any gas) at Standard Temperature and Pressure
(STP) is 22.4 Liters.[the volume of 45 water bottles]
The standard conditions (STP) are: Temp: 0 C Pressure: 1.0 atmosphere
Calculate the volume of the following @ STP: 2.0 moles of
Oxygen
3.5 moles of oxygen
3.5 moles of Carbon Dioxide
Warm UP In a 10.O gram Oreo
cookie, the cream has a mass of 2.0 grams. What is the % composition (by mass) of the cookie?
Calculate % Composition*from lab data
1. Add the masses of each element to find the total mass.
2. Divide the mass of one element by the total mass, multiply by 100 (then add % sign)
3. Repeat step 2, for each element
4. Add up all the %s to make sure they = 100%
An 8.2 gram piece of Mg combines with 5.4 grams of Oxygen. What is the % composition?
1. Add the masses to find the total.
2. Divide the mass of one element by the total mass. Multiply by 100 (add %)
3. Repeat for other elements.
4. Do the %’s add to 100?
Calculate % composition*from the chemical formula
What is the percent composition of Propane, C3H8 ?
1. Assume you have 1 mole of the substance.
2. Determine molecular mass of the substance.
3. Divide the mass of one element by the molecular mass. Multiply by 100. (add ‘%’)
4. Repeat for other elements in the substance.5. Do the %s add to 100?
Determine the percent compositionOf water.
Warm Up
Determine the % Composition of MgCl2
If you have 100g of magnesium chloride how many grams of magnesium are there?
If you have 84g of magnesium chloride how many grams of magnesium are there?
Empirical Formulas:
The empirical formula may or may not give the actual formula.
For any compound, its empirical formula is the lowest whole number ratio of elements.
Empirical Formula form molecular formula
Compound Chemical Formula Empirical Formula(lowest whole number ratio)
Hydrogen Peroxide
H2O2 HO
Glucose C6H12O6 C? H? O?
Acetic Acid C2H4O2
Ammonia NH3
Empirical Formula Use lab data to determine ratio of
elements.
Calculating empirical formula *from lab data (% comp data)
The % composition is 20.1% Hydrogen and 79.9% Carbon.
Determine the empirical formula.
1. Assume 100g total (easy conversion from %)
So:20.1g of Hydrogen79.9g of Carbon
2. Determine the number of moles of each element.
Convert the grams of each element to a number of moles.
20.1 g H /1.01 g/mole
_____ moles of Hydrogen
79.9 g C / 12.01 g/mole
____moles of Carbon
C H
Subscripts must be whole numbers.
3. Divide each amount of moles by the smallest number.
C
H
Warm-Up
What is the empirical formula for Oxalic Acid? H2C2O4
Empirical formula is the lowest whole number ratio of elements in a compound.
A chemical compound has the empirical formula CH2O
The molar mass of the compound is 180g/mol
What is the molecular formula?
