Chem Class- October 19, 2009

Last class we had our test for Unit 2 and today we got our test back. We hope everyone did well!
After that, Mr.D did a small balloon experiment:

Now we're on to something new!

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Today we were introduced to the Mole.

Now let's get this straight. We're not talking about the kind of burrowing animal or the so called 'beauty spot', but the SI unit for the amount of substance . It is equal to the number of atoms in exactly 12.0 grams of carbon-12 (6.02 x 10 to the power of 23)

1 mole is equal to 602 000 000 000 000 000 000 000 or 6.02 x 10 to the power of 23. This is a really big number and it is known as Avogadro's number. Let's say we had that number equal to dollars. If we divided that number up among the six billion people on Earth, every person would have $100 000 000 000 000 each.

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Many people tried to see how gases could combine. John Dalton, for example, looked at masses of gasses but he could see no pattern:

• 11.1g of H2 reacts with 88.9g of O2
• 46.7g of N2 reacts with 53.3g of O2
• 42.9g of C reacts with 57.1g of O2

The reason he couldn't see a pattern is because 1 molecule of H2 doesn't have the same mass as 1 molecule of O2.

Joseph Gay-Lussac tried combining gases on volume:

• 1 L of H2 reacts with 1 L of Cl2----->2 L of HCl
• 1 L of N2 reacts with 3 L of H2----->2 L of NH3
• 2L of CO reacts with 1 L of O2----->2 L of CO2

As you can see, gases combine in simple whole number ratios.

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AVOGADRO'S HYPOTHESIS
Equal volumes of any gas at a constant temperature and pressure contain equal numbers of molecules.