Chemistry 101 Dr. Don DeCoste 109 Chemistry Annex decoste@illinois.edu 244-5959 2-3 pm Mondays and 10-11 am

Thursdays By appointment

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To Do… http://chem.illinois.edu Slides on the website (after each

lecture) Discussion tomorrow. Lon-Capa (HW2 Type 1 due

Monday, February 3 by 7 pm).

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Subscripts Represent Numbers

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Chemical Reactions Occur By Number of Molecules

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Clicker Question

The mass of a single atom of hydrogen is:

a) 1.674 x 10-24 gb) 6.022 x 1023 gc) 1.000 moled) 1.008 ge) 2.016 g

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Clicker Question

The mass of a single atom of hydrogen is:

a) 1.674 x 10-24 gb) 6.022 x 1023 gc) 1.000 moled) 1.008 ge) 2.016 g

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Clicker QuestionYou have a 12.01 g sample of carbon and a 1.008 gram sample of hydrogen. The number of carbon atoms is:

a) greater than the number of hydrogen atoms. b) less than the number of hydrogen atoms.c) the same as the number of hydrogen atoms.d) I have no idea.

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Clicker QuestionYou have a 12.01 g sample of carbon and a 1.008 gram sample of hydrogen. The number of carbon atoms is:

a) greater than the number of hydrogen atoms. b) less than the number of hydrogen atoms.c) the same as the number of hydrogen atoms.

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The Mole Concept: Why?

We can count by weighing (relative masses).

Reactions occur by number of particles, we must deal with masses, so we must have a way of converting between number and mass.

Atoms/molecules are very small!

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Clicker QuestionYou have equal mass samples of copper (Cu) and magnesium (Mg). Which sample contains the greater number of atoms?

a) The sample of copper. b) The sample of magnesium.c) The samples contain the same number of atoms. d) I have no idea.

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Clicker QuestionYou have equal mass samples of copper (Cu) and magnesium (Mg). Which sample contains the greater number of atoms?

a) The sample of copper. b) The sample of magnesium.c) The samples contain the same number of atoms.

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Clicker QuestionYou have a 10.0 g sample of copper (Cu). What mass of magnesium (Mg) do you need to have the same number of Mg atoms as Cu atoms?

a) More than 10.0 g of Mg.b) Less than 10.0 g of Mg.

c) 10.0 g of Mg.d) I have no idea.

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Clicker QuestionYou have a 10.0 g sample of copper (Cu). What mass of magnesium (Mg) do you need to have the same number of Mg atoms as Cu atoms?

a) More than 10.0 g of Mg.b) Less than 10.0 g of Mg.

c) 10.0 g of Mg.

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Calculate…You have a 10.0 g sample of copper (Cu).

Determine the mass of magnesium (Mg) such that the number of copper atoms and magnesium atoms are equal.

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