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## PowerPoint Slideshow about ' Ch. 10 Chemical Quantities' - alesia

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3 Methods of Measuring

- Counting
- Mass
- Volume

Example 1

- If 0.20 bushel is 1 dozen apples, and a dozen apples has a mass of 2.0 kg, what is the mass of .050 bushel of apples?

Example 1

- Count: 1 dozen apples = 12 apples
- Mass: 1 dozen apples = 2.0 kg apples
- Volume: 1 dozen apples = 0.20 bushels

apples

Conversion Factors:

- 1 dozen2.0 k.g1 dozen

12 apples 1 dozen 0.20 bushels

Avogadro’s Number

- Named after the Italian scientist Amedo Avogadro di Quaregna
- 6.02 x 10 23

Mole (mol)

- 1 mol = 6.02 x 10 23 representative particles
- Representative particles: atoms, molecules ions, or formula units (ionic compound)

Example 2 (atoms mol)

- How many moles is 2.80 x 10 24 atoms of silicon?

Example 3 (mol molecule)

- How many molecules of water is 0.360 moles?

The Mass of a Mole of an Element

- The atomic mass of an element expressed in grams = 1 mol of that element = molar mass

Molar mass S

Molar mass Hg

Molar mass C

Molar mass Fe

Example 4 (mol gram)

- If you have 4.5 mols of sodium, how much does it weigh?

Example 5 (grams atoms)

- If you have 34.3 g of Iron, how many atoms are present?

The Mass of a Mole of a Compound

- To find the mass of a mole of a compound you must know the formula of the compound
- H2O H= 1 g x 2

O= 16 g

18 g = 1 mole = 6.02 x 10 23

molecules

Example 6 (gram mol)

- What is the mass of 1 mole of sodium hydrogen carbonate?

Example 6

- Sodium Hydrogen Carbonate = NaHCO3
- Na=23 g
- H=1 g
- C=12 g
- O=16 g x3
- 84 g NaHCO3 = 1 mol NaHCO3

Mole-Volume Relationship

- Unlike liquids and solids the volumes of moles of gases at the same temperature and pressure will be identical

Avogadro’s Hypothesis

- States that equal volumes of gases at the same temperature and pressure contain the same number of particles
- Even though the particles of different gases are not the same size, since the gas particles are spread out so far the size difference is negligible

Standard Temperature and Pressure (STP)

- Volume of a gas changes depending on temperature and pressure
- STP= 0oC (273 K)

101.3 kPa (1 atm)

Standard Temperature and Pressure (STP)

- At STP, 1 mol = 6.02 X 1023 particles = 22.4 L of ANY gas= molar volume

Example 7

- At STP, what volume does 1.25 mol He occupy?

Example 8

- If a tank contains 100. L of O2 gas, how many moles are present?

Calculating Molar Mass from Density

- The density of a gas at STP is measured in g/L
- This value can be sued to determine the molar mass of gas present

Example 9

- A gaseous compound of sulfur and oxygen has a density of 3.58 g/L at STP. Calculate the molar mass.

Percent Composition

- The relative amounts of the elements in a compound
- These percentages must equal 100

Example 10

- Find the percentage of each element present in Al2 (CO3)3

Example 10

- Al2(CO3)3
- Al= 27 g x 2 = 54 g / 234 g x 100=23%
- C= 12 g x 3 = 36 g/ 234 g x 100= 15%
- O = 16 g x 9 = 144 g / 234 g x 100=62%

234 gAl2(CO3)3

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