Evidences of rx• Changes: – Color – Temperature – PS: production of gas, ppt – pH – smell• Fire
Replacement reaction• A + BC AC + B (A and B are metals)• “Single replacement”• What to look for Element + compound on each side of equation
Reaction # 1 Replacement• Zn(s) + HCl(aq)• 6M HCl in test tube (~ ½ full, measure)• ~ 1 t Zn in balloon (tare balloon, weigh)• Complete and balance equation, what is in the balloon at the end of the reaction? PS? – relate to stoichiometry• What evidences that a reaction occurred?• What is LR, ER??
Replacement Reaction # 2• Zn(s) + CuSO4(s) Cu(s) + ZnSO4(aq)• If there is a limited amount of copper sulfate, the solution will become colorless as all the copper ions are converted to copper metal• The Zinc ions produced are colorless
• Zinc is considered more active than copper• Zinc “replaces” copper in the compound – Later when we look at redox reactions – Electrons move from Zinc (making it a soluble Zinc ion) to copper (making it an insoluble metal) – The sulfate ions are called “spectator ions” – they do not play a part in the reaction
Reaction # 3 Replacement• Fe(s) + CuSO4(aq)• Steel wool in test tube, add copper sulfate to ½ the level of the steel wool – observe• Make observations, complete balanced equation
Fe(s) + CuSO4(aq) FeSO4(aq) + Cu(s)Steel wool on the left,, “copper wool” on the rightNote original blue color of copper sulfate solutionIn left hand solutionOn the right all the copper ions have “plated out”as copper metal, the blue color of the solution isgone!
Reaction #4 Replacement Reaction• Cu(s) + ZnSO4(aq)• ¼ test tube or beaker of ZnSO4 add copper turnings• Observe
• Copper does not push Zinc out of a compound spontaneously – You can “push” this reaction in the reverse by “pushing “ an electrical current through it!!
Do all possible replacement reactions occur?• Activity series “what can replace what”• Metals and H:…….
Activity Series for Metals Can be used to predict the outcome of replacement reactions• Listed Most Active to Least Active• Li K Ba Ca Na Mg--- Al Mn Zn Cr Fe Co Ni Sn PbHCu Ag Hg Pt Au• Any element on the list can replace from a compound elements to its right• Everything to the left of H can push H out of an acid• Everything to the left of the “---” can push H out of water• Elements to the right of H do not react with acids by replacing H (copper has a redox reaction with concentrated nitric acid, but does not react with other acids)