1. Parts of Equations K(s) + O 2 (g)  K 2 O(g) 1)Reactants - the starting materials in a chemical reaction; everything to the left of the arrow 2)“+” means reacts with or combines with ex: potassium combines with oxygen 3) “  ” means yields or produces 4) Products  the substances formed during a chemical reaction; everything to the right of the arrow

2. K(s) + O 2 (g)  K 2 O(g) 5) “s”  element/compound is in the solid state 6) “g”  element/compound is in the gas state 7) “l”  element/compound is in the liquid state 8) “aq”  element/compound is in the aqueous state a) aqueous  solid is dissolved in a liquid

3. K(s) + O 2 (g)  K 2 O(g) 9) “ 2 ” is a subscript which is the number written below and to the right of a chemical symbol * indicates the number of each type of atom * can NEVER change the subscripts in a chemical equation– NEVER!!!!!! The above equation reads: Solid potassium combines with gaseous oxygen to yield gaseous potassium oxide

4. Meaning of Subscripts Subscripts tell us the number of atoms in a compound How many of each?? H 2 O = _______ hydrogen, _______ oxygen H 2 O = 2 hydrogen, 1 oxygen O HH

5. KNO 3 KNO 3 = ___potassium, __nitrogen, __oxygen KNO 3 = 1 potassium, 1 nitrogen, 3 oxygen K N O O O

6. What to do with parenthesis? Subscripts that are outside the parenthesis ONLY go to the atoms inside the ( ). Multiply the subscript outside the ( ) by any subscript inside the ( ).

7. Pb(NO 3 ) 2 # of Pb : __ (Because Pb is NOT inside the ( ), it does not get multiplied by 2) # of N : _____ x ______ = ______ inside the ( ) outside the ( ) total # of O : _____ x ______ = ______ inside the ( ) outside the ( ) total 1 1 22 326 Pb N O O O N O O O

8. Ni 2 (SO 4 ) 3 # of Ni: ____ (Because Ni is NOT inside the ( ), it does not get multiplied by the 3) # of S: ____x ____ = ____ inside the ( ) outside the ( ) total # of O: ____ x ____ = ____ inside the ( ) outside the ( ) total 2 133 4312

9. Meaning of Coefficients Coefficients tell us the number of molecules in an equation All atoms to the right of a coefficient get multiplied by the coefficient Stop multiplying by the coefficient when you get to a “+” or a “  ”

10. 2H2O2H2O How many water molecules? ________ How many hydrogen atoms? ________ How many oxygen atoms? __________ O HH O HH 2 2 X 2 = 4 2 X 1 = 2

11. 3KNO 3 How many potassium nitrate molecules? ____________ How many potassium atoms? ________ How many nitrogen atoms? __________ How many oxygen atoms? ___________ 3 3 X 1 = 3 3 X 3 = 9 K N O O O K N O O O K N O O O

12. 2FeCl 3 How many Iron (III) chloride molecules? __________ How many iron atoms? _____________ How many chloride atoms? ___________ 2 2 X 3 = 6 2 X 1 = 2 Fe Cl Fe Cl

13. Now you try!

14. How many of each? 2H 2 # of H = 4

15. How many of each? 3H 2 O 3(H 2 O) # of H = 6 # of O = 3

16. How many of each? 2AlCl 3 2(AlCl 3 ) # of Al = 2 # of Cl = 6

17. How many of each? 2Li 3 N 2(Li 3 N) # of Li = 6 # of N = 2

18. 2HNO 3 2(HNO 3 ) # of H = 2 # of N = 2 # of O = 6

19. How many of each? 2FeCl 3 2(FeCl 3 ) Fe = 2 Cl = 6

20. How many of each? Al(HCO 3 ) 3 Al = 1 H = 3 C = 3 O = 9

21. How many of each? 3[Pb(NO 3 ) 2 ] Pb = 3 N  3X1 = 3X2 = 6 O  3X3 = 9X2 =18

22. How many of each? 2Fe 2 (SO 4 ) 3 2[Fe 2 (SO 4 ) 3 ] Fe = 4 S  2 X1 =2 X 3 = 6 O  2 X 4 = 8 X 3 = 24

23. How many of each? 2Ni 3 (PO 4 ) 2 2[Ni 3 (PO 4 ) 2 ] Ni  6 P  2X1 = 2X2 = 4 O  2X4 = 8X2 = 16

24. End Here!

25. Balancing Equations We must balance equations in order to comply with the law of conservation of mass. K + O 2  K 2 O # of K _______ # of K ______ # of O ______ ReactantsProducts 1 2 2 1 Are there they same number of each type of atom on both sides of the equation? ______ No

26. This equation violates the Law of Conservation of Mass. We must therefore balance the equation so that there are the same number of each type of atom on both sides of the equation. When you balance equations, you do so by using coefficients You can NEVER change the SUBSCRIPTS!!! To get the total number of atoms, you must multiply the coefficient by the subscript.

27. Lets see what happens when we place a coefficient of 4 in front of the K on the reactant side and a 2 in front of the K 2 O on the product side in the equation ___K + O 2  ____ K 2 O # of K _______ # of K ______ # of O ______ ReactantsProducts 4 2 4 4 2 2

28. Now you try some!

29. Balanced or Not? 2Na + Cl 2  2NaCl Reactant Side Product Side Balanced? Na Cl

30. Balanced or Not? 2Na + Cl 2  2NaCl Reactant Side Product Side Na22 Cl22

31. Balanced or Not? Ag + H 2 S  Ag 2 S + H 2 Reactant Side Product Side Balanced? Ag H S

32. Balanced or Not? Ag + H 2 S  Ag 2 S + H 2 Reactant Side Product Side Balanced? Ag12No H22Yes S11

33. Balanced or Not? 2Cl 2 + 2NaBr  2NaCl + Br 2 Reactant Side Product Side Balanced? Cl Na Br

34. Balanced or Not? 2Cl 2 + 2NaBr  2NaCl + Br 2 Reactant Side Product Side Balanced? Cl42No Na22Yes Br22Yes

35. Balanced or Not? 2Al + 6HCl  2AlCl 3 + 3H 2 Reactant Side Product Side Balanced? Al H Cl

36. Balanced or Not? 2Al + 6HCl  2AlCl 3 + 3H 2 Reactant Side Product Side Balanced? Al22Yes H66 Cl66Yes

37. Balanced or Not? 3H 2 O + 4Fe  Fe 2 O 3 + 3H 2 Reactant Side Product Side Balanced? H O Fe

38. Balanced or Not? 3H 2 O + 4Fe  Fe 2 O 3 + 3H 2 Product Side Reactant Side Balanced? H66Yes O33 Fe42No

39. Balanced or Not? 3BaCl 2 + 2K 3 (PO 4 )  Ba 3 (PO 4 ) 2 + 6KCl Reactant Side Product Side Balanced? Ba Cl K PO 4

40. Balanced or Not? 3BaCl 2 + 2K 3 PO 4  Ba 3 (PO 4 ) 2 + 6KCl Reactant Side Product Side Balanced? Ba33Yes Cl66Yes K66 PO 4 22Yes

41. Which letter will balance it? ___ Cu + ___ S  ___Cu 2 S (A) 2, 1, 2(B) 2, 1, 1(C) 1, 1, 2 Reactant Side Product Side Balanced? Cu S

42. Which letter will balance it? 2Cu + 1S  1Cu 2 S (A) 2, 1, 2(B) 2, 1, 1(C) 1, 1, 2 Reactant Side Product Side Balanced? Cu22Yes S11

43. Which letter will balance it? ___Al + ___ O 3  ___Al 2 O 3 (A) 2, 1, 1 (B) 2, 3, 4, (C) 4, 3, 2 Reactant Side Product Side Balanced? Al O

44. Which letter will balance it? ___Al + ___ O 3  ___Al 2 O 3 (A) 2, 1, 1 (B) 2, 3, 4, (C) 4, 3, 2 Reactant Side Product Side Balanced? Al22Yes O33

45. Which letter will balance it? __HCl + ___F 2  ___HF + ____Cl 2 (A)1, 1, 2, 1 (B) 2, 1, 1, 2(C) 2, 1, 2, 1 Reactant Side Product Side Balanced? H Cl F

46. Which letter will balance it? ___HCl + ___F 2  ___HF + ___Cl 2 (A)1, 1, 2, 1 (B) 2, 1, 1, 2(C) 2, 1, 2, 1 Reactant Side Product Side Balanced? H22Yes Cl22Yes F22