molar mass, and other simple math! 1 st of all, what is a molar mass? it is the sum of the masses of the atoms. We did this when we did molar mass, but not much. for instance - what is the molar mass of CO 2 ? you take the mass of the carbon and add the mass of 2 oxygens x 2 then add them up! =43.99 grams! not too bad! try finding the molar mass of water! great! now, what if you had 5 moles of water, how much would that weigh? take the moles (5) x the mass of water ( g/mole) and get a total mass of grams

HU? O = g/ mole C = g/ mol = g/mol O O O How much do these compounds weigh? CO C O O if these atoms have these weights...

great, now lets try percent composition. it is the part BY MASS that each element is in a compound. All percents are just part over total. so there you go, find the part, find the total. for instance, if I had a compound that had 33 grams of nitrogen and 45 grams of oxygen what is the percent composition of each? 1st find the total grams = 78 grams. now divide each there is another way to do this, and that is from the formula itself say you knew you had some diphosphours decaoxide, and you wanted to know how much oxygen you had. 1st- P 2 O 10 has a total mass of... ( yes molar mass of this), P= x 2= and oxygen is x 10 = g total is grams and oxygen % is 159.9/ =.72 so 72% oxygen by mass

O O O = g/ mole = g/mol what is the % nitrogen in this compound if these atoms have these weights... more math? O

= O O O O = g/ mole = g/mol = st find the parts and the whole

O = g/ mole = g/mol so the part that is Nitrogen is = O O O this means "out of" it also means divided by.3685, or 36.9 %

now lets try emperical formula- also called simplest formula it is the smallest ratio of the elements. if you are given a formula, it may or may not be the simplest CO 2 S4 O 8 SO2 H 2 O HNO 3 C6 H 12 O 6 CH2O How to do it: 1st you are given grams amounts, or %s. either way, turn them into moles ( divide by molar mass) 2nd, looking at the answer from 1, divide all by smallest, this gives you whole numbers!

· Product-a substance that is produced by a chemical reaction. Ca Br Ca Br ·Reactants- Substance that enters a chemical reaction. Chemical Reactions

Chemical Equation · Wor d Eqn. Have words in them Formula Eqn. Have symbols of the element < ·Formula Equation - Ca +O 2 → CaO ·Word Equation - Calcium + Oxygen = Calcium Oxide

3 things that must be true of chemical reactions include- 1. they must represent known facts ( you can’t make them up, the reaction actually has to happen) how do you know? 2.Formula’s must be correct ( balance ionic compounds, write covalent compound correctly) 3.Law of conservation of mass Balance reaction! Use coefficients to make sure reactant amounts and product amounts are equal H 2 + O 2 H 2 O

Balancing reactions Make sure the numbers of elements on both sides are the same. Add large numbers called coeffiencts to balance. Before balancing; H 2 + O 2 = H 2 O after 2 H 2 + O 2 = 2 H 2 O

Nitrogen gas and Sulfer create Dinitrogen tetrasulfide Na 2 O + H 2 O = NaOH Ca(OH) 2 + Na = NaOH + Ca Fe + H 2 O = Fe 2 O 3 + H 2

Na + O 2 = Na 2 O MgO + K = K 2 O + Mg Fe + O 2 = Fe 2 O 3

Cl H H Mg Types of reactions all reactions can be grouped into 5 general types 1. synthesis - 2 or more reactants turn into ONE product + Cl O HH O + Mg O H O H

2. Decomposition- the reverse of synthesis, this takes ONE REACTANT and makes 2 or more products N N H H H H OO N HH N OO CO3 ⇒ C + O 2 NO 2 ⇒ N 2 + O 2 NN