The Mole Concept Avogadro’s Number = x 10 23

Counting Atoms Chemistry is a quantitative science - we need a "counting unit." MOLEThe MOLE 1 mole is the amount of substance that contains as many particles (atoms or molecules) as there are in 12.0 g of C-12.

The Mole is Developed Carbon AtomsHydrogen AtomsMass Ratio Number Mass (amu) Mass carbon / Mass hydrogen amu = 12 1 amu 1 24 [2 x 12] 2 [2 x 1] 24 amu = 12 2 amu [10 x 12] 10 [10 x 1] 120 amu = amu [50 x 12] 50 [50 x 1] 600 amu = amu 1 (6.02 x ) x (12) Avogadro’s number (6.02 x ) x (1) (6.02 x ) x (12) = 12 (6.02 x ) x (1) 1 Avogadro’s number Avogadr oPaper Avogadr oPaper

Amadeo Avogadro (1776 – 1856) 1 mole = or x thousands millions billionstrillions quadrillions ? There is Avogadro's number of particles in a mole of any substance. Particles in a Mole Amedeo AvogadroAmedeo Avogadro ( ) never knew his own number; it was named in his honor by a French scientist in its value was first estimated by Josef Loschmidt, an Austrian chemistry teacher, in 1895.

Amadeo Avogadro (1776 – 1856) 1 mole = or x thousands millions billionstrillions quadrillions ? There is Avogadro's number of particles in a mole of any substance. Particles in a Mole

Careers in Chemistry - Philosopher Q: How much is a mole? A: A mole is a quantity used by chemists to count atoms and molecules. A mole of something is equal to 6.02 x “somethings.” 1 mole = Q: Can you give me an example to put that number in perspective? A: A computer that can count 10,000,000 atoms per second would take 2,000,000,000 years to count 1 mole of a substance.

Counting to 1 Mole Is that right? A computer counting 10 million atoms every second would need to count for 2 billion years to count just a single mole. Lets look at the mathematics. Therefore 1 year has 31,536,000 seconds or x 10 7 sec. A computer counting 10,000,000 atoms every second could count x atoms every year. Finally, 6.02 x atoms divided by x atoms every year equals 1,908,929,477 years or approximately 2 billion years! x sec = 1 year 365 days 1 year1 day 24 hours60 min 1 hour 60 sec 1 min = 31,536,000 sec

How Big is a Mole? One mole of marbles would cover the entire Earth (oceans included) for a depth of three miles. One mole of $100 bills stacked one on top of another would reach from the Sun to Pluto and back 7.5 million times. It would take light 9500 years to travel from the bottom to the top of a stack of 1 mole of $1 bills.

Avogadro’s Number  A MOLE of any substance contains as many elementary units (atoms and molecules) as the number of atoms in 12 g of the isotope of carbon-12.  This number is called AVOGADRO’s number N A = 6.02 x particles/mol  The mass of one mole of a substance is called MOLAR MASS symbolized by MM  Units of MM are g/mol  Examples H 2 hydrogen2.02 g/mol Hehelium4.0 g/mol N 2 nitrogen28.0 g/mol O 2 oxygen32.0 g/mol CO 2 carbon dioxide44.0 g/mol

1 Mole of Particles

Example Questions You have 98.4g of Na. How many moles of Na do you have in sample? You have 127g of CO2 in sample. How many moles of CO2 do you have? 7.2 moles of Ca is equal to how many grams of Ca?

Example questions

Example Questions

Limiting reactant The reactant in a chemical reaction that limits the amount of product that can be formed. The reaction will stop when all of the limiting reactant is consumed.

Excess Reactant Excess Reactant - The reactant in a chemical reaction that remains when a reaction stops when the limiting reactant is completely consumed. The excess reactant remains because there is nothing with which it can react.

A 50.6 g sample of Mg(OH)2 is reacted with 45.0 g of HCl according to the reaction: Mg(OH)2 + 2 HCl --> MgCl2 + 2 H2O What is the yield of MgCl2?

Practice

Practice

Theoretical Yield The theoretical yield is the maximum amount of product which can be produced (in an ideal world). In the "real" world it is difficult to produce the amount obtained for the theoretical yield. A percent yield is often used to show how close to ideality one has obtained in a chemical synthesis.

Percent Yield equation

Practice problems Experimentally the chemist found that 46.5g of NaCl was collected at the end of the experiment. However in his calculations he found that he should have produced 50g of NaCl. What was his percentage yield?

Practice problems Given the reaction: 2H + O  H2O In this reaction you have 16 grams of both H and O. After the reaction you collected16.98 grams H2O what is your percentage yield?

Practice NH3 + O2 → NO + H2O Assuming you had 43 grams of NH3 and 23 grams O2. You actually collected grams of NO. What was your percentage yield of NO?