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The Mole , Ch. 10 You need a calculator from this chapter on. PowerPoint PPT Presentation

The Mole , Ch. 10 You need a calculator from this chapter on. *The mole was invented as a way to describe number of atoms. *1 mole = 6.02 x 10 23 things. 602,000,000,000,000,000,000,000 things. What if you had a mole of \$1 bills?.

The Mole , Ch. 10 You need a calculator from this chapter on.

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The Mole, Ch. 10You need a calculator from this chapter on.

• *The mole was invented as a way to describe number of atoms.

• *1 mole = 6.02 x 1023 things.

• 602,000,000,000,000,000,000,000 things.

What if you had a mole of \$1 bills?

• In a mole of water, there are 6.02 x 1023 molecules of H2O.

• Pass around 1 mole of water.

*Converting moles to # of particles

• Convert 3 moles of aluminum to number of atoms of aluminum.

• Convert 7 moles of methane to molecules of methane.

*Molar Mass

• One mole of an atom will weigh ___ grams (shown on the periodic table).

*Convert moles to grams

• Mg. 1 mole  ? grams

• 6.94 grams

• 3 moles Be  ? grams

• 27 grams.

• 2.5 x 1022 atoms of Na  grams Na?

• .96 grams

• 3 moles of CH4 to grams?

• 48 grams.

• 4 moles of HF to grams?

• 80 grams

Try it:

• 6 moles of H2O to grams.

• 126 g of NaF to moles.

• 108 grams, 3 moles

• Molar mass of Uranium a ball of uranium with a radius of 1.3 inches weighs a pound.

• *A mole of any gas takes up 22.4 L (at STP). This is Avogadro’s Hypothesis.

• This is like a cube with sides of 28.2 cm.

• One mole of He, H, O, N, etc. will all take up 22.4 L.

• Question: How many He atoms are there in 22.4 L?

• Question: How many H2 molecules are there in 22.4 L?

• How many moles of O2 in 44.8 liters of O2?

• How many L in 4 moles of N2?

• 89.6 L

• STP 0 C, pressure = 1 atm (101.3 kPa)

Gas Density:

• Often is measured in g/L.

• What is the density of H2 gas at STP?

• .089 g/L

• Gas density

• Try: 55 E23 particles of He to volume of gas. Try: 55 E23 particles of He to grams of gas.

• Be able to solve mole problems.

• Compare a mole of eggs to a dozen eggs.

• What is a mole useful for?

• *Gas density to molar mass.

• Exp: 2.86 g/L.

Percent Composition

• Is the percent by mass of each element in the compound.

• *Percent Composition from mass data:

• 5.4 g of oxygen and 8.2 g of magnesium in a 13.6 gram compound.

• 60.3% Mg, 39.7% O

• *Percent composition from the chemical formula Find the amount of grams of each element in 1 mole of the compound, then find the %.

• C3H8

• 81.8% C, 18% H

• How many grams of O are present in 36 grams of H2O?

• 32 grams O

• *Empirical formula: Expresses the atoms in their lowest ratio.

• *Molecular formula: Expresses the atoms in their actual abundance.

• Exp: H2O2 HO

*Determining Empirical Formula:

• 25.9% N

• 74.1 % O

• Assume 100 g of the compound, find the # of moles, then find the whole number ratio.

• Answer = 2 mol N, 5 mol O

• The molecular formula is always a whole number multiple of the empirical formula.

• Empirical formula to Molecular formula If the empirical formula is CH4N and the molecular molar mass is 60 g/mol, what is the molecular formula?

• C2H8N2

Assignment

• Draw and explain with words:

• If you could have a mole of anything, what would you want and why?

• Can be creative and funny.