1. What is a mass spectrometer and how does it work? 2. What kind of ion is produced to create a mass spectrum? 3. What is a mass spectrum? End

 Haven’t you always wanted to know what’s actually going into your body?  Naming Practice  Stations practice  Naming big molecules  Naming little molecules  Naming organic molecules  Naming inorganic molecules  Name it all!

 LT 2.11 – I can explain the concept of the mole and why it is an adequate means by which to express the amount of given substance.  LT 2.12 – I can determine the empirical and molecular formula for any compound given its constituent parts. I can also calculate percent composition for each element in that compound.

 Recall that Avogadro proposed that 1 mole = x particles.  If you have 1 mole this means you have x of this substance.  This works because particles are really small!

 One mole of Carbon- 12 holds x particles.  This can be applied to any substance and always has the same number of particles.  This isotope was easier to use than Carbon-13 or C-14.

 We can convert between the amount of a substance to moles by using the molar mass.  To do this, use the atomic mass on the periodic table.

 You have g of C 6 H 12 O 6, how many moles do you have?

 Percent composition - is the percent by mass of each element present in a compound.  How much of one thing is in another?

 Water, H2O is a great example.  One mole of water is grams  In that compound there are two moles of H atoms and 1 mole of O atoms.

 Calculate the percent by weight of sodium (Na) and chlorine (Cl) in sodium chloride (NaCl) molecule.

 Molecular Formula is what the actual molecule is!  Molecular Formula - a formula giving the number of atoms of each of the elements present in one molecule of a specific compound.

 Empirical means observed, or determined from experimentation!  Empirical formula is the smallest whole number ratio of moles of each element in a compound.  CaCl 2 --> there is 1 mole of calcium for every 2 moles of chlorine

 1. If you have masses go onto step 2.  If you have %. Assume the mass to be 100g, so the % becomes grams.  2. Determine the moles of each element.  3. Determine the mole ratio by dividing each elements number of moles by the smallest value from step 2.  4. Double, triple … to get an integer if they are not all whole numbers

 Turn each of the molecular formulas to the right into empirical formulas.

 The atomic weight of element X is 100. g/mol grams of X combines with 32.0 g of oxygen. What is the simplest formula for the resulting compound? The atomic weight of oxygen = 16.0 g/mol.

 Which of the following substances has an empirical formula that is different from that of the others? (a) Erythrose: C 4 H 8 O 4 (b) Propionic acid: C 3 H 6 O 2 (c) Acetic acid C 2 H 4 O 2 (d) Glucose C 6 H 12 O 6

 KHAN YOU DO IT?  prep/mcat/physical- processes/stoichiometry/v/molecular-and- empirical-formulas prep/mcat/physical- processes/stoichiometry/v/molecular-and- empirical-formulas  Watch video and answer Q’s

 Complete the stations review independently or with your table.

 Quantitative on Ch. 2 on Monday  Answers to practices