Using Dimensional Analysis to solve chemical quantities The Mole Using Dimensional Analysis to solve chemical quantities U

Click here to watch the TedEd video on the Mole

What is a Mole? A mole is a counting unit. We use other counting units in real life. For example, how many pieces of paper are in a ream of paper?_______ Is it easier to count 5000 pieces of paper or 10 reams of paper? A mole is defined as the SI base unit that measures the number of carbon atoms in exactly 12 grams of carbon-12.

Why was carbon-12 used as a standard for comparison? Hydrogen was initially used because scientists recognized it as the least massive element, but as technology improved, it was discovered that atoms had isotopes, so a particular isotope of an element had to be chosen. Carbon-12 was chosen because carbon is very common, is a solid, is easy to transport and store.

Why do we use moles? How large is an atom? - About 5 million Hydrogen atoms can fit on the head of a pin, so atoms are very small. - Because atoms are so small, chemists needed a convenient unit to count by. That unit is the mole. - 1 mole = 6.022 x 1023 representative particles Silicon atoms arranged on the face of a crystal as taken by a scanning tunneling microscope that “feels” the cloud of electrons that forms the outer surface of atoms.

What is a representative particle? Examples of representative particles are: - atoms (used when examining elements) Example: Ca, O, He - molecules (used when examining covalently bonded compounds) Example: H2O, PCl5, CO2 - formula units ( used when examining ionically bonded compounds) Example: NaCl , K2SO4, FeS

Using the Periodic Table Atomic Number Atomic Mass The atomic mass is an average of all of the naturally occurring isotopes of that particular element. The number is equal to 55.847 amu’s (atomic mass units). 1 amu = 1gram/mole. This number is also known as the molar mass.

Who came up with the number 6.022 x 1023? Amadeo Avogadro mathematically determined this number through his experimentation with gases. His principle states that “equal volumes of all gases at the same temperature and pressure contain the same number of molecules.”

Avogadro’s Law and Gases at STP STP means standard temperature and pressure. Standard temperature is 0⁰C and 1 atmosphere 1 mole of any gas at STP occupies 22.4L of space. Certain elements form diatomic molecules of gases in their natural state. These elements are H2, O2, N2, F2, Cl2, Br2, I2

Equivalencies 1 mole = 6.02 x 1023 atoms, molecules or formula units The atomic mass of a substance is equal to the molar mass of the substance in g/mol. 1 mol of any gas at STP = 22.4L

Go to the periodic table! Conversion Chart 1 mole Mass (g) Volume (L) Representative Particles (atoms, molecules or formula units) Go to the periodic table! 6.022 x 1023 22.4 L

Calculations How many atoms are in 5.2 mol of Ca? How many formula units are in 0.003 mol of CaCl2? How many moles are in 9.2 x 1023 molecules of water?

Calculations Determine the mass, in grams of 5.3 mol of potassium. Determine the number of moles in 13.8g of MgCl2. Determine the mass of 8.32 x 1024 molecules of Cl2.

Calculations 7. Determine the mass, in grams, of 6.3 liters of oxygen gas (O2) at STP. 8. Determine the volume of 86.3g of CO2 at STP. 9. Determine the number of atoms of radon gas present in 7.51L of gas at STP.

% Composition What is the general formula for calculating a %? What is the % composition of Sulfur in Ag2S? Find the molar mass of 2Ag’s and 1 S Divide the molar mass of the sulfur by the molar mass of Sulfur + 2 Ag’s, then multiply by 100.

Solution for % Composition Problem What is the % composition of Sulfur in Ag2S? 2 Ag = 2 x 107.87 g/mol = 215.74 g/mol 1 S = 1 x 32.07 g/mol = 32.07 g/mol b. X 100 = 12.94% What would be the % composition of the Silver in Ag2S? 32.07 g/mol 215.74 g/mol + 32.07 g/mol

Bibliography http://ts4.mm.bing.net/images/thumbnail.aspx?q=4534876311388471&id=d713e9daed16c3c95ed6e10424383f07 https://encrypted-tbn1.google.com/images?q=tbn:ANd9GcQNg9kP2NkS5sphSqhEffmVNqdc7Gt0ju4M4hy9NRWq-Vdwy8VPeg https://encrypted-tbn0.google.com/images?q=tbn:ANd9GcRZp3xD5KV_41Yh3vSqpJP82fhfEXJB3TfPA9sc-hddq2SioA6J7Q https://encrypted-tbn2.google.com/images?q=tbn:ANd9GcS6a6082nHUT0lTgBwQC-raiktGW4L9Epu-WxR3hDxtlVFemAjzRg https://encrypted-tbn1.google.com/images?q=tbn:ANd9GcT58RO6CPvyqQhtLAeW7bJYvYKsxNoQVvaGa9BpsJ14toLg-axZ https://encrypted-tbn0.google.com/images?q=tbn:ANd9GcTFHIA3cr1sLHtlHnWnTYD8cL1yr-nxHcnRZxeQ59ff9zlrNOES https://encrypted-tbn3.google.com/images?q=tbn:ANd9GcSDvvPNlW87iK5ZrjpVGWty4J2DJ37PQIy9XxH_kMFfUdYC7 http://books.google.com/books?id=1rZDv93KFWoC&pg=PT17&lpg=PT17&dq=why+was+carbon+12+chosen+as+the+standard&source=bl&ots=a0BwuHNIOt&sig=wlPYmHAC1Hy7EFtu4gnf7ffWiC0&hl=en&sa=X&ei=t9tZULfFBqrC0QHjp4DQCQ&ved=0CEMQ6AEwBA#v=onepage&q=why%20was%20carbon%2012%20chosen%20as%20the%20standard&f=falseQZo https://encrypted-tbn3.google.com/images?q=tbn:ANd9GcR78A4MWdd-4gaWBmKEQuvaFWNgMyy6_G2cYx0YK8Cw0BGtg_Ocbw