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# Introduction to the Mole

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## Sarah McKee

on 30 November 2011

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#### Transcript of Introduction to the Mole

1 Dozen grains of rice = 0.21 g ? grains of rice = 1.94g Let the
units guide you! Avogadro's number = the mole 6.02x10 23 Visualize a mole... An Avogadro's number of standard soft drink cans would cover the surface of the earth to a depth of over 200 miles. If you had Avogadro's number of unpopped popcorn kernels, and spread them across the United States of America, the country would be covered in popcorn to a depth of over 9 miles. If we were able to count atoms at the rate of 10 million per second, it would take about 2 billion years to count the atoms in one mole. O S 8 16 16.0 32.1 Molar Mass-
the mass of one mole of any pure substance. molar mass of an element (g/mol)-
Equals the atomic mass of the element in grams molar mass of a compound-
equals the sum of the molar masses of the elements making up the compound Find the molar mass of magnesium Find the molar mass of chlorine. Find the molar mass of magnesium chloride. Find the molar mass of aluminum oxide. The MOLE How many moles of atoms are there in 8.0 g of Mg? How many atoms are in 0.7g of He? Do the following three problems by yourself on your notes...

1. How many atoms are in 3.5 g of silicon?

2. How many formula units are in 32.6 g of potassium oxide?

3. How many molecules are in 0.25 g of dinitrogen pentoxide? ?atoms = 3.5 g Si 1 mol Si 6.02*10 atoms 23 28.1 g Si 1 mol Si x x = 7.5*10 atoms 22 ? f.u. K O = 32.6 g K O 1 mol K O 6.02*10 f.u. K O 2 2 2 2 x x 94.2 g K O 2 1 mol K O 2 = 2.1 * 10 f.u. K O 23 2 ? molecules N O = 0.25 g N O 1 mol N O 6.02*10 molecules x x 108 g N O 1 mol N O 2 5 2 5 2 5 2 5 2 5 = 1.4 * 10 molecules N O 21 2 5 Do you GET it? In chemistry, what do we mean when we refer to a mole?

a. a fuzzy little creature
b. a dozen
c. 6.02 * 10 23 Answer: C The periodic table tells you how many grams are in a mole of atoms of any element. This is known as the:

a. gramole

b. molar mass

c. atomic mass unit Answer: b What is the molar mass of aluminum chloride?

a. 62.5 g/mol
b. 133.5 g/mol
c. 116.5 g/mol Answer: b How many moles of atoms are in 12.0 g of helium?

a. 1

b. 2

c. 3

d. 4 Answer: c How many molecules of water are in 4.8 moles of water?

a. 7.97 x 10
b. 2.89 x 10
c. 5.20 x 10
d. 1.61 x 10 -24 24 25 23 Answer: b
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