ch 11: the mole. section 11.1 measuring matter dozen= 12 ream= 500 pair= 2 gross= 144
Post on 21-Dec-2015
219 Views
Preview:
TRANSCRIPT
Ch 11: The Mole
Section 11.1 Measuring Matter
• Dozen=• 12
• Ream=• 500
• Pair=• 2
• Gross=• 144
• What is a mole?
• It is the SI base unit used to measure the amount of a substance
• Abbreviated mol
• Represents particles
• Is also called Avogadro’s number
6.02 x 1023 (3 significant figures)
• Remember conversion factors?
• 12 roses = 1 dozen
• So, 3.5 dozen= ? Roses
= 42
Well, 6.02 x 1023 atoms (or any representative paticles) = 1 mol
• Review Scientific Notation
• Review Rounding
• Example:• 3.50 mol sucrose has how many molecules?
• Work practice problems 1-3
• Example:• How many moles are in 3.58 X 1020 atoms of Ca?
• Work practice problems 4-7
closure
• How is a mole similar to a dozen?• What is the relationship between avagadr
o’s number & one mole?• Why do chemists use moles?
• **worksheet: The mole & Avogadro’s number
• STOP
Section 11.2 Mass & the Mole
• Different particles (atoms) have different masses.
• Remember atomic mass. – Each element has its own specific mass.– Therefore each compound has its own
specific mass.
• Molar mass (g/mol)-mass in grams of any pure substance
• The molar mass of any element is numerically equal to its atomic mass.
• Thus…1 mol Mn = 54.94 g/mol Mn = 6.02 x 1023 atoms Mn
• Example:
• 1 mol Zn =
65.4 g/mol
• 1 mol O2 =
32.0 g/mol
• Practice
• 3 mol Zinc =
196 g/mol Zn
• 1 mol H2O =
18.0g/mol H2O
• 1 mol sulfuric acid =
98.1 g/mol H2SO4
Mass Mole conversions
• Example:
• Calculate the mass in grams of 0.0450 mol Cr.
• Work Practice problems 1-4
• Hydrate: CuSO4·5H2O
4) Calculate the mass in grams of 2.45 mol of CaCl2·2H2O
Mole Mass conversions
• Example:
• Determine the number of moles for 25.5 g Ag. (mass mol)
• Work practice problems 5-7.
**worksheet: moles & mass
Mass Atom Conversion
• Example:– How many atoms of gold (Au) are in a pure
nugget having the mass of 25.0g?– Practice problems 1-5
Atom Mass Conversion
• Example
• A party balloon contains 5.50 x 1022 atoms of helium (He) gas. What is the mass in grams of the helium?
• Practice problems 6-10.
Mole Mole
Example
• According to the following balanced equation, how many moles of O2 is produced from 3.00 moles of CuO?
2CuO 2Cu + O2
Practice problems 1 & 2.
Section 11.4 Empirical & Molecular Formula
• Percent Composition is the percent by mass of each element in a compound.
Example:
• If we had 100 g of a sample of some new compound contains 55g of element X & 45 g of element Y. What is the % of element X & Y?
• If we already know the _chemical formula for a compound, you can calculate its percent composition.
• % by mass=
• Mass of element in 1 mol of compound X 100
Molar mass of compound
• Ex. Determine the percent composition of H2O.
• (If you had 350. g of water, then how much is oxygen?)
• Practice problems 1-3.
• Empirical Formula is the smallest whole number ratio of the elements.
• Calculating Empirical formula from percent composition:
• Directions:• The percent should be assumed to be 100
g & converted to moles. Then we figure out the mole ratio by dividing each by the smallest mole.
POEM:
1. Percent to Mass
2. Mass to Mole
3. Divide by small
4. Multiply til whole.
• Example 1
• The percent composition of an oxide of sulfur is 40.05% S & 59.95% O.
• Example 2
• Determine the empirical formula for methyl acetate which has the following chemical analysis:48.64% C, 8.16% H, & 43.20% O.
• Practice Problems
• **worksheet: determining empirical formulas
top related