Mole

Moles How a chemist measures the amount of matter in a substance counting unit - number of molecules ; atoms ; particles MOLE TRIANGLE MOLES Grams Volume # molecules or # particles Way to convert Road Map – map out where you start to where you end Conversions are along side the arrows Formula wt. or gram-form. mass 6.02 x L How? Divide in (  ) Multiply out (x)

Moles How many moles of oxygen in 1 mole of Al 2 (SO 4 ) 3 ? How many moles of oxygen in 1 mole of CuSO 4   5H 2 O? Gram atomic/formula mass (molecular mass) = mole of substance Al 2 (SO 4 ) 3 Avogadro’s Number Volume of Gas at STP 6.02 x mole = 22.4 L 3 x 4 = 12 4(5 x 1)+ Al 2 S 3 O 12 2 x 27 3 x x 16 = 192 = 54 (the parantheses are Like a distribution in math) = 96 Gram form mass is the sum of the total mass of each element in the formula Add all the masses up = 342 g/mol Atoms / mole = 9

Percent Composition “ parts per hundred” divide the quantity under consideration by the total quantity involved Part whole x 100 What is the percent by mass of chlorine in CaCl 2 ? What is the percent by mass of water in Na 3 PO 4 12H 2 O ? What is the percent by mass of water in hydrate: Mass of hydrate:132.4g Mass of anhydrous124.2g Part whole x 100 2Cl CaCl 2 X 100 2(35.45) X 100 % Cl = 63.89% For any % composition problem--you must first find the formula mass of the compound Find the formula mass first 3 x 23 = 69 1 x 31 = 31 4 x 16 = 64 + Mass of water 12 x 18 = 216 Add them all up = 380 g/mol Now find % 216 g/mol 380 g/mol X 100 =56.8 % To find mass of water - Subtract the two #’s = 8.2 g Now find % 8.2 g g X 100 = 6.2 % Table T

Empirical Formula the simplest integer ratio in which atoms combine to form a compound 75 % C and 25% H What is the empirical formula? Molecular Formula the actual ratio of the atoms in a molecule The molecular mass of a compound with an empirical formula of CH 2 is 28g, what is the molecular formula? 1. Change % to grams75g 25g 2. Find number of moles 75g 12g 25g 1 g Divide by the smallest number 4. find ratio 1 to 4 5.formula CH 4 1. Change % to grams 2. Find number of moles 3. Divide by the smallest number 4. find ratio (becomes the subscripts) 5. Write the formula 2. Find the molecular mass of the compound 3. Divide the mass given in the problem by the Molecular mass 4. Multiply subscripts by Answer to step 2 3. C 2 H 4 1. Find formula mass (1) = 14 g/mol 2.28g 14 g/mol = Write down your given

Density Table T : D = MVMV For a gas at STP D = Formula wt 22.4L CO 2 = [12 + 2(16)] 22.4 L

Reactions

Chemical Reaction (aq) (g) (l) (s) = + heat  Pt Chemical sentence that describes a reaction Reactants Products and Yields or produces Equilibrium- reaction forward and reverse liquid gas Solution dissolved in water Heat was added catalyst solid

1. Determine if the reaction is combustion (C x H y +O 2 CO 2 + H 2 O) or not Balancing Equations Reactants Products Law of Conservation of Mass-Energy Mass, energy, & charge are conserved (MEC) Check your work!!!! 4. Continue to add coefficients until you have same number on both sides 2. Find the most complicated formula 3. By inspection use coefficient to balance atoms (each element!!) Balance equations by using coefficients If it is: If it’s not: 2. Start with the carbons & make sure they are the same on both sides of the arrow. 3. Next balance the H’s 4. Finally balance the O’s- watch out they are separated on the product side!

Hydrogen plus oxygen yields water Nitrogen plus hydrogen yields ammonia How many H’s do I have on both sides of the equation? 2 Now, How many O’s do I have on both sides of the equation? 2 on left, 1 on right Put a 2 as a coefficient in front of the H 2 O H 2 + O 2 = H 2 O OR H 2 + O 2 H 2 O H 2 + O 2 2H 2 O How does that affect your number of H’s? How do we fix it? 2H 2 + O 2 2H 2 O Place a 2 in front of The H on left side to balance Think distribution like in math. N 2 + H 2 NH 3 N 2 + 3H 2 2NH 3 Remember Diatomics!! ! Look at both sides Pick one element and balance first Place 2 in front of NH 3 Now go back and balance H’s

Types of Chemical Reactions Synthesis (Combination ) Combination of two separate things to make ONE new thing. Decomposition Single Replacement Double Replacement Examples Break apart a compound into two or more things. + An element (all alone by itself) takes the place of an element in a compound to form a new compound and a new element by itself. A + B AB + + The positive charge elements swap. Two new compounds are formed ONLY IF one of the new compounds is insoluble. A compound is burned with oxygen and produces CO 2 and H 2 O. The compound can contain C, H, & O. Combustion + + Examples Example CREATE/Construct 2 1 Sr + I 2 SrI 2 4Fe+3O 2 2Fe 2 O 3 + (decompose) 1 2 AB A + B Examples 2H 2 O 2 2H 2 O + O 2 Deconstruct Mg(Cl0 3 ) 2 MgCl 2 + 3O 2 Stud kicks out wimp A + BC AC + B Stud meter = Table J Higher elements replace lower. Higher elements are more reactive. Mg + H 2 SO 4 MgSO 4 + H 2 F 2 + 2NaBr Br 2 + 2NaF Swap Meet Use TABLE F to figure out if swap meet happens. Innies vs Outies AB + CD AD+ CB (s) + - CdBr 2 + Na 2 S CdS (s) +2NaBr Burning Complete Combustion: C x H y + O 2 CO 2 + H 2 0 Incomplete Combustion: C x H y + O 2 CO + H 2 0

Mole Mall Expansion Moles Grams Liters # particles Mass PT x10 23 Use coefficients Set up a proportion