Redox Reactions What are the Products?
For the purposes of Chapter 4, an oxidation-reduction (redox) reaction is a reaction in aqueous solution between an element and a compound. The element can be a metal or a nonmetal. The compound will be an acid, base or salt.
Oxidation is the loss of electrons and reduction is the gaining of electrons. One cannot happen without the other. In these reactions, one component loses electrons and a different component gains them.
If the element is a metal or hydrogen, then it will lose electrons to change into its corresponding cation. The cation from the reactant compound will gain the electrons to change into its corresponding element. Then the new cation will join with the anion to form a new compound.
If the element is a nonmetal (other than hydrogen), then it will gain electrons to change into its corresponding anion. The anion from the reactant compound will lose its electrons, changing into its corresponding element. Then the new anion will join with the cation to form a new compound.
On this web page, we will focus on the first type of redox reaction - where the element is a metal or hydrogen.
EXAMPLES: Write a balanced molecular equation for each of the following aqueous reactions. Indicate whether or not the reaction will occur, and briefly explain why.
(1) iron + tin(II) nitrate
| reactant 1 | reactant 2 |
---> |
product 1 | product 2 | |
| element | Fe | Sn | |||
| cation | Sn2+ | Fe2+ | |||
| anion | NO3- | NO3- | |||
| compound | Sn(NO3)2 | Fe(NO3)2 | |||
| state | (s) | (aq) | (aq) | (s) |
Answer:
Fe(s) + Sn(NO3)2(aq) ---> Fe(NO3)2(aq) + Sn(s)
(2) hydrochloric acid + chromium
| reactant 1 | reactant 2 |
---> |
product 1 | product 2 | |
| element | Cr | H2 | |||
| cation | H+ | Cr3+ | |||
| anion | Cl- | Cl- | |||
| compound | HCl | CrCl3 | |||
| state | (aq) | (s) | (g) | (aq) |
Answer:
6 HCl(aq) + 2 Cr(s) ---> 3 H2(g) + 2 CrCl3(aq)
PRACTICE EXERCISES:
Write a balanced molecular equation for each of the following aqueous reactions.
QUESTIONS:
| 1. | magnesium + copper(II) sulfate |
| 2. | gold(III) nitrate + zinc |
| 3. | aluminum + lead(II) acetate |
| 4. | manganese + nitric acid |
| 5. | acetic acid + silver |
| 6. | hydrogen + platinum(II) nitrate |
| 7. | nickel(II) bromide + cobalt |
| 8. | zinc + calcium sulfate |
| 9. | tin(II) nitrate + aluminum |
| 10. | lead + silver acetate |
1:00-2:00
ANSWERS (If you do not understand any of these, the go ask your instructor) :
| 1. | Mg(s) + CuSO4(aq) --> MgSO4(aq) + Cu(s) |
| 2. | 2 Au(NO3)3(aq) + 3 Zn(s) --> 2 Au(s) + 3 Zn(NO3)2(aq) |
| 3. | 2 Al(s) + 3 Pb(C2H3O2)2(aq) --> 2 Al(C2H3O2)3(aq) + 3 Pb(s) |
| 4. | Mn(s) + 2 HNO3(aq) --> Mn(NO3)2(aq) + H2(g) |
| 5. | 2 HC2H3O2(aq) + 2 Ag(s) --> H2(g) + 2 AgC2H3O2(aq) |
| 6. | H2(g) + Pt(NO3)2(aq) --> 2 HNO3(aq) + Pt(s) |
| 7. | NiBr2(aq) + Co(s) --> Ni(s) + CoBr2(aq) |
| 8. | Zn(s) + CaSO4(aq) --> ZnSO4(aq) + Ca(s) |
| 9. | 3 Sn(NO3)2(aq) + 2 Al(s) --> 3 Sn(s) + 2 Al(NO3)3(aq) |
| 10. | Pb(s) + 2 AgC2H3O2(aq) --> Pb(C2H3O2)2(aq) + 2 Ag(s) |
Tutoring Cent
last updated 14 December 2008
