1. Chemical Reactions

2. Signs of a Chemical Reaction: -Evolution of light and heat -Formation of a gas -Formation of a precipitate -Color change

3. Law of Conservation of Mass 4g32g 36g 4 H 2 O 4 H 2 O -Mass in neither created or destroyed in a chemical rxn. -Total mass stays the same -Atoms can only be rearranged

4. Chemical Reactions (rxn) PRODUCTS

6. Describing reactions: - Individual atom = “atom” -Covalent substance = “molecule” -Ionic substance = “unit” The coefficients (whole # before formula) = #moles of substance

7. Balancing Equations

8. Steps to Balancing Equations: 1) Write the unbalanced equation 2) Count the number of atoms on each side of the arrow 3) Add coefficients to make numbers equal (Coefficient x subscript = # of atoms) 4) If necessary, multiple entire equation by a whole number to remove any decimal value 5) If necessary, reduce coefficients to lowest whole number values Double Check- by counting the number of atoms

9. Hints- 1) Balance one element at a time 2) Update ALL atom counts after adding a coefficient 3) If an element appears more than once on a side of the reaction, leave it to last 4) Treat polyatomic ions as if they were single atoms “ 1 SO 4 ” instead of “1 S ” and “ 4 O”

10. Examples Aluminum and copper (II) chloride react to form Copper and Aluminum chloride Al + CuCl 2 Cu + AlCl 3 2 33 2 Al Cu Cl 12 13 36 12 13 2 6

11. When Hydrogen gas and Oxygen gas are combined in the presence of electricity, water is formed. H 2 + O 2 H2OH2O HOHO 2 2 2 1 2 4 2 4 2 2

12. C 8 H 18 + O 2 CO 2 + H 2 O CHOCHO 8 18 2 123123 8 8 16 1836 9 1725 50 12.5 () 2 225 16 18 16 36 5041

14. 1) Combination (Synthesis) Rxn A + XAX Two or more substances combined to form a new compound Produces only 1 product

15. 2)Combustion Reaction A + O 2 B A substance combines with oxygen to produce a product and energy If A=hydrocarbon, then B = CO 2 + H 2 O 4Na + O 2 2Na 2 O C 3 H 8 + 5O 2 3CO 2 + 4H 2 O

16. 3) Decomposition Rxn ABA + B A compound is broken down into 2 or more parts Only has 1 reactant 2KBr2 K + Br 2

17. 4) Single Displacement (replacement) rxn A + BXAX + B One element replaces another in a compound Metal will replace metal (+) Nonmetal will replace nonmetal (-)

18. Lithium Potassium Calcium Sodium Magnesium Aluminum Zinc Chromium Iron Nickel Lead Hydrogen Bismuth Copper Mercury Silver Platinum Gold Activity Series  Metals can replace other metals provided that they are above the metal that they are trying to replace  Metals above hydrogen can replace hydrogen in acids.  Metals from sodium upward can replace hydrogen in water

19. Fluorine Chlorine Bromine Iodine The same is true for halogens. Fluorine is the most reactive Fe 2 O 3 + 2 AlAl 2 O 3 + 3Fe 2NaCl + F 2 2NaF + Cl 2 MgCl 2 + Br 2 NR

20. 5) Double Displacement (replacement) rxn AX + BYBX + AY ions in two compounds “change partners” cation of one compound combines with anion of the other

21. The ions of two compounds exchange places in an aqueous solution to form two new compounds. One of the products formed will be an insoluble substance called a precipitate PB(NO 3 ) 2(aq) + 2KI (aq) PbI 2(s) + 2KNO 3(aq) H 2 SO 4(aq) + Ca(OH) 2(aq) 2H 2 O (l) + CaSO 4(aq) (Neutralization rxn: Acid + BaseWater + Salt)

22. Stoichiometry

23. Stoichiometry - The study of quantities of materials consumed and produced in chemical reactions. CALCULATING MASSES OF REACTANTS AND PRODUCTS 1.Balance the equation. 2.Convert mass or volume to moles, if necessary. 3.Set up mole ratios. 4.Use mole ratios to calculate moles of desired substituent. 5.Convert moles to mass or volume, if necessary. 1.Balance the equation. 2.Convert mass or volume to moles, if necessary. 3.Set up mole ratios. 4.Use mole ratios to calculate moles of desired substituent. 5.Convert moles to mass or volume, if necessary.

24. 6.50 grams of aluminum reacts with an excess of oxygen. How many grams of aluminum oxide are formed. 1. Identify reactants and products and write the balanced equation. Al + O 2 Al 2 O 3 43 2

25. 6.50 grams of aluminum reacts with an excess of oxygen. How many grams of aluminum oxide are formed. 2. Convert to values to mole Al + O 2 Al 2 O 3 43 2 6.5 g Al 1 mol 26.98g Al = 0.24 mol Al

26. 6.50 grams of aluminum reacts with an excess of oxygen. How many grams of aluminum oxide are formed. 3. Setup mole ratios 4. Calculate moles for desired quantity Al + O 2 Al 2 O 3 43 2 o.24 molX mol = 4 0.24 2 X X = 0.12 mol Al 2 O 3

27. 6.50 grams of aluminum reacts with an excess of oxygen. How many grams of aluminum oxide are formed. 5. Convert to desired value for final answer 0.12 mol Al 2 O 3 1 mol 101.98 g Al 2 O 3 = 12.24g

28. #2 How many liters of oxygen gas, at STP, can be collected from the complete decomposition of 50.0 grams of potassium chlorate? 2 KClO 3 (s)  2 KCl(s) + 3 O 2 (g) 50g1 mol 122.55 g =.41 mol KClO 3.41 molX mol = 2.41 3 x x = 0.62 mol O 2 o.62 mol 1 mol 22.4 L 13.89L O 2

29. MOLARITY : Concentration of a solution. total combined volume substance being dissolved

30. MOLARITY: 2M HCl What does this mean?

31. MOLARITY CALCULATION How many grams of NaCl are required to make 0.500L of 0.25M NaCl? 0.500 L0.25 mol 1 L = 7.3 g NaCl 58.44 g 1 mol

32. 63.55 g Cu 1 mol Cu How many grams of Cu are required to react with 1.5 L of 0.10M AgNO 3 ? 1.5 L.10 mol AgNO 3 1 L = 4.8 g Cu Cu + 2AgNO 3  2Ag + Cu(NO 3 ) 2 1 mol Cu 2 mol AgNO 3 ? g 1.5L 0.10M

33. I want to make PB & J sandwiches: I have: 4 slices of bread 1 Jar of jelly 1 jar of Peanut Butter How many sandwiches can I make ? Why can’t I make more? Bread- Limiting reactant PB and Jelly are said to be excess reactants

34. Limiting Reactant Limiting Reactant – used up in a reaction – determines the amount of product Excess Reactant Excess Reactant – added to ensure that the other reactant is completely used up – cheaper & easier to recycle

35. 1.Write a balanced equation. 2. For each reactant, calculate the amount of product formed. 3. Smaller answer indicates: – limiting reactant – amount of product How to Solve limiting reactant problems:

36. A chemical reaction between lead (II) nitrate and sodium iodide produces a precipitate of solid lead (III) iodide and sodium nitrate. If I have 25g of lead (II) nitrate and 15g of sodium iodide, how much sodium nitrate is produced? + 2NaI (aq) PbI 3(s) + 2NaNO 3 (aq) 25g 15g Pb(NO 3 ) 2 (aq) 25g1 mole (Pb) 331g 1 mole (Na) 85g 1 mole (Pb) 2 mole (Na) = 12.84 g Pb(NO 3 ) 2 (aq) X g

37. NaI: 15g 150 g 1 mole NaI 2 mole NaI 2 mole (Na) 1 mole (Na) 85 g = 8.5 g Which is the limiting Reactant? Pb(NO 3 ) 2 (aq) = 12.84gNaI = 8.5g

38. When the experiment was actually done, 7.4g of NaNO 3 were produced. What is the percent yield for the experiment? Measured in Lab Calculated on paper

39. % Yield = 7.4 g 8.5g X 100 = 87.1 % Problem #2: If 100g of propane (C 3 H 8 ) combines with 1o0g of oxygen to produce carbon dioxide and water, how water will be produced? If during the experiment 42g of water is produced, what is the percent yield? H 2 O = 45g% Yield = 93.3% C 3 H 8 + 5O 2 3CO 2 + 4H 2 O