Practice!

1. Practice! • How many atoms are in each of the following compounds? • H2SO4 • Ca(NO3)2 • (NH4)3PO4 • C6H12O6 • 2 H2O • 10 CO2 7 atoms! 9 atoms! 20 atoms! 24 atoms! 6 atoms! 30 atoms!

2. CHEMISTRY ICHAPTER 9 CHEMICAL REACTIONS

3. Chemical reaction- • the process by which the atoms of one or more substances are rearranged to form different substances.

4. Evidence of a chemical reaction: 1. Release of a gas Zinc is added to hydrochloric acid producing hydrogen gas and solid zinc chloride.

5. 2. Color changes two liquids are mixed solid and a liquid mixed

6. 3. Formation of a precipitate • a precipitate is a solid product formed by the reaction of two aqueous solutions. • It is abbreviated ppt. Aqueous sodium iodide and aqueous lead (II) nitrate produce solid lead (II) iodide and aqueous sodium nitrate.

7. 4. Changes in heat and light • all reactions either absorb or release energy Sodium peroxide (yellow powder) and zinc powder (gray powder in the bowl) are combined Water is then squirted in & the mixture ignites

8. Writing Chemical Equations: reactants  products From now on USE PENCIL!! yield EXAMPLE: Na + Cl2 NaCl

9. Writing Chemical Equations: • Reactants—the starting substance(s). • Products—the substance(s) formed during the reaction.

10. Possible symbols in chemical equations: • + plus •  yields • (s) solid • (l) liquid • (g) gas • (aq) aqueous •  equilibrium • N.R. no reaction •  light or heat is added • Catalyst ( & catalysts are written above the yield sign)

11. Examples: To what is the arrow pointing? H2O2 (aq) H2O (l) + O2 (g) H2 (g) + O2 (g) H2O (g) MnO2  CaCO3 CaO (s) + CO2 (g)

12. Lavoisier, 1788 Conservation of Mass Because of the principle of the conservation of mass, an equation must be balanced. It must have the same number of atoms of the same kind on both sides.

13. Writing and Balancing Chemical Equations You must be able to write the symbol from the words and vice versa. Example: Write the equation for the formation of sodium hydroxide and hydrogen, from the reaction of sodium with water.

14. Write the equation for the formation of sodium hydroxide and hydrogen, from the reaction of sodium with water. • Write the formulas of all reactants to the left of the arrow and all products to the right of the arrow. Sodium + water sodium hydroxide + hydrogen Translate the equation and be sure the formulas are correct. Na + H2O NaOH + H2

15. Write the equation for the formation of sodium hydroxide and hydrogen, from the reaction of sodium with water. • Once the formulas are correctly written, DO NOTchange them. • Use coefficients (numbers in front of the formulas), to balance the equation. • DO NOT CHANGE THE SUBSCRIPTS! • Coefficients are always whole numbers. _____Na + _____H2O ____NaOH + _____H2

16. Subscripts vs. Coefficients • The subscripts tell you how many atoms of a particular element are in a compound. • The coefficient tells you about the quantity, or number, of molecules or formula units of the compound.

17. Begin balancing with an element that occurs only once on each side of the arrow. • Ex: Na 2 2 2 _____Na + _____H2O ____NaOH + _____H2 When you are finished, you should have equal numbers of each element on either side of the equation Na H O 2 Na H O 2 4 4 2 2

18. To determine the number of atoms of a given element in one term of the equation, multiply the coefficient by the subscript of the element. Ex: In the previous equation (below), how many hydrogen atoms are there? 4 2 2 2 ____Na + _____H2O ____NaOH + _____H2

19. Helpful Hints: • Take one element at a time, working left to right except for H and O. Save H for next-to-last, and O until last. • IF everything balances except for O, and there is no way to balance O with a whole number, double all the coefficients and try again. (Because O is diatomic as an element) • (Shortcut) Polyatomic ions that appear on both sides of the equation should be balanced as independent units. (NH4)2SO4 (aq) + BaCl2 (aq)  BaSO4 (s) + NH4Cl (aq)

21. Balancing Equations ___ Al(s) + ___ Br2(l) ---> ___ Al2Br6(s) 2 3

22. Practice: • Balance the equation for the formation of magnesium nitride from its elements. Mg2+ N3- Mg3N2 ____Mg + ____N2 3 ____Mg3N2

23. Balance the reaction of sodium metal with chlorine gas to form sodium chloride. Na+ Cl- NaCl ____Na + ____Cl2 2 ____NaCl 2

24. Ex: NH3 + O2 NO2 + H2O • H can be balanced by placing a 2 in front of NH3 and a 3 in front of H2O. Then put a 2 in front of NO2 for nitrogen to balance. _____NH3 + _____O2____NO2 + ____H2O 2 2 3

25. _____NH3 + _____O2____NO2 + ____H2O 2 2 3 • Now all that is left to balance is the oxygen. There are 2 O on the reactant side and 7 on the product side. Our only source of oxygen is the O2. Any whole number we place in front of the O2 will result in an even number of atoms. The only way to balance the equation is double all the coefficients.

26. _____NH3 + _____O2____NO2 + ____H2O 2 2 3 • Double all the coefficients, then add the 7 for the O2. ( ) 2 ____NH3 + _____O2____NO2 + ____H2O 2 2 3 = _____NH3 + _____O2____NO2 + ____H2O 4 7 4 6

27. Practice equations: ____H2 + ____O2 ____H2O ___NH3 + ____O2 ____NO2 + ____H2O ___Ca + ___H2O  ___Ca(OH)2 + ___H2

28. __NH4Cl +__Ca(OH)2 __NH3 + __H2O+__CaCl2 ___ZnO + ___HCl  ___ZnCl2 + ___H2O ____K + _____F2 _____KF ____C2H4 + ____O2 ____CO2 + ____H2O

29. Types of Chemical Reactions

30. Types of Reactions • There are five types of chemical reactions we will talk about: • Synthesis reactions • Decomposition reactions • Single displacement reactions • Double displacement reactions • Combustion reactions • You need to be able to identify the type of reaction and predict the product(s)

31. Steps to Writing Reactions • Some steps for doing reactions • Identify the type of reaction • Predict the product(s) using the type of reaction as a model • Balance it Don’t forget about the diatomic elements! (BrINClHOF) For example, Oxygen is O2 as anelement. In a compound, it can’t be a diatomic element because it’s not an element anymore, it’s a compound!

32. Synthesis reaction (combination reaction)- • the combination of two or more substances to form a compound Elem. or cmpd. + elem. or cmpd  cmpd. General form A + B  AB • The product in a reaction will have different properties from either of the reactants that formed it.

33. Practice • Predict the products. Write and balance the following synthesis reaction equations. • Sodium metal reacts with chlorine gas Na(s) + Cl2(g)  • Solid Magnesium reacts with fluorine gas Mg(s) + F2(g)  • Aluminum metal reacts with fluorine gas Al(s) + F2(g)  2 2 NaCl(s) MgF2(s) 2 AlF3(s) 2 3

34. Decomposition Reaction: • is the breakdown of one substance into two or more other substances • compound  two or more elements • AB  A + B • 2 H2O  2H2 + O2 • 2 HgO  2Hg + O2

35. Decomposition Exceptions • Carbonates and chlorates are special case decomposition reactions that do not go to the elements. • Carbonates (CO32-) decompose to carbon dioxide and a metal oxide • Example: CaCO3  CO2 + CaO • Chlorates (ClO3-) decompose to oxygen gas and a metal chloride • Example: 2 Al(ClO3)3  2 AlCl3 + 9 O2 • There are other special cases, but we will not explore those in Chemistry I

36. Practice • Predict the products. Then, write and balance the following decomposition reaction equations: • Solid Lead (IV) oxide decomposes PbO2(s)  • Aluminum nitride decomposes AlN(s)  Pb(s) + O2(g) 2 2 Al(s) + N2(g)

37. Practice Identify the type of reaction for each of the following synthesis or decomposition reactions, and write the balanced equation: N2(g) + O2(g) BaCO3(s)  Co(s)+ S(s)  NI3(s)  Nitrogen monoxide Synthesis 2 NO (g) Decomposition BaO(s) + CO2 (g) Co2S3 (s) 2 3 (make Co be +3) Synthesis 2 3 Decomposition N2 (g) + I2 (s)

38. Single Replacement Reaction: • One element replaces another element in a compound. • A metal can replace a metal (+) OR a nonmetal can replace a nonmetal (-). element + compound  element + compound A + BC  AC + B When H2O splits into ions, it splits into H+ and OH- (not H+ and O-2 !!)

39. Single Replacement Reactions • Write and balance the following single replacement reaction equation: • Zinc metal reacts with aqueous hydrochloric acid Zn(s) + HCl(aq) ZnCl2 + H2(g) Note: Zinc replaces the hydrogen ion in the reaction 2

40. Single Replacement Reactions • Sodium chloride solid reacts with fluorine gas NaCl(s) + F2(g)  NaF(s) + Cl2(g) Note that fluorine replaces chlorine in the compound • Aluminum metal reacts with aqueous copper (II) nitrate Al(s)+ Cu(NO3)2(aq) Cu(s) + Al(NO3)3(aq) 2 2 2 3 3 2

41. To determine if a single replacement reaction will take place you must compare the activities of the elements involved. • For metals, use the Activity Series. A metal will replace any metal below it on the activity series.

42. Activity Series of Metals and Halogens MetalsHalogens Deceasing activity Lithium Fluorine Potassium Chlorine Calcium Bromine Sodium Iodine Magnesium Aluminum Zinc Chromium Iron Nickel Tin Lead HYDROGEN Copper Mercury Silver Platinum Gold Will Na replace Cr in a single replacement reaction? Yes!

43. Activity Series of Metals Lithium Potassium Barium Calcium Sodium Magnesium Aluminum Zinc Iron Cadmium Nickel Tin Lead Hydrogen (a nonmetal) Copper Mercury Silver Gold Platinum Metals from Li to Na will replace H from water and acids; metals from Mg to Pb will replace H from acids only. Decreasing Activity Practice: N.R. ___I2 + ___NaCl  ___AgNO3 + ___Mg  ___KBr + ___F2 ___Mg(NO3)2 + ____Cu  2 2 ___Mg(NO3)2 + ___Ag 2 2 ___KF + ___Br2 N.R.

44. Double Replacement Reaction: • Two elements replace each other in compounds. • occur when a metal replaces a metal in a compound and a nonmetal replaces a nonmetal in a compound AB + CD  AD + CB MgCO3 + 2HCl  MgCl2 + H2CO3 AgNO3 + NaClAgCl + NaNO3

45. Double Replacement Reactions • Think about it like “foil”ing in algebra, first and last ions go together + inside ions go together • Example: AgNO3(aq) + NaCl(s)  AgCl(s) + NaNO3(aq) • Another example: K2SO4(aq) + Ba(NO3)2(aq)  KNO3(aq) + BaSO4(s) 2

46. In order for double replacement reaction to take place, one of the products must be an insoluble solid (ppt), a gas, or water.

48. Compound Precipitate Formed? • BaSO4 _______ • Pb(NO3)2 _______ • Ag2S _______ • PbCl2 _______ • NH4Cl _______ • Cr PO4 _______ Yes No Yes Yes No Yes

49. 2 __NaNO3 + __BaSO4 Na+ NO3- Ba2+ SO42- __Na2SO4 + __Ba(NO3)2 __NaOH + __Fe(NO3)3 NaNO3 BaSO4 3 __NaNO3 + __Fe(OH)3 3 Na+ NO3- Fe3+ OH- NaNO3 Fe(OH)3

50. Practice • Predict the products. Balance the equation • HCl(aq) + AgNO3(aq)  • CaCl2(aq) + Na3PO4(aq)  • Pb(NO3)2(aq) + BaCl2(aq)  • FeCl3(aq) + NaOH(aq)  • H2SO4(aq) + NaOH(aq)  • KOH(aq) + CuSO4(aq)  HNO3(aq) + AgCl(s) 3 2 Ca3(PO4)2(s) + NaCl(aq) 6 PbCl2(s) + Ba(NO3)2(aq) Fe(OH)3(s) + NaCl(aq) 3 3 2 2 H2O(l) + Na2SO4(aq) 2 K2SO4(aq) + Cu(OH)2(s)