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Chemical Reactions

This guide covers the key concepts of chemical reactions, focusing on ionic equation writing and their classifications. It explores redox reactions, where oxidation numbers change, exemplified by calcium and iron reactions. Non-redox reactions, which show no change in oxidation numbers, are explained via ionic compounds like sodium chloride and their solubility in water. The double replacement reaction mechanism is discussed, alongside predicting insoluble precipitates using solubility rules. The document also illustrates complete and net ionic equations for better understanding.

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Chemical Reactions

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  1. Chemical Reactions with Ionic Equation Writing

  2. 2 Classifications • 1. Redox Reaction • There is a change in oxidation number between reactant side and product side • Ca + Fe3(PO4)2 Ca3(PO4)2 + Fe Oxidation # Ca = 0 Fe2+ PO43- Ca2+ PO43- Fe = 0 Diatomics have an oxidation # of zero

  3. 2 Classifications (cont.) • 2. Non-Redox Reaction • No change in oxidation number between reactant side and product side • NaCl + K2SO4 Na2SO4 + KCl Oxidation # Na+ Cl- K+ SO42- Na+ SO42- K+ Cl- Typically 2 ionic compounds reacting together

  4. Non Redox Reactions • If a compound is soluble in water, • it exists as ions in water. • If a compound is insoluble in water, • It exists as a precipitate (solid) in water

  5. We are going to assume all reactant compounds are soluble in water as we practice making ions…..

  6. Non Redox Reactions • If soluble in water: • NH4F will exist as • NH4+ • F- NH4+ F-

  7. Non Redox Reactions • If soluble in water: • H2CO3will exist as • H+ • CO32- H+ CO32- But really 2H+ H+

  8. Non Redox Reactions • If soluble in water: • Al(NO3)3will exist as • Al3+ • NO3- NO3- NO3- Al3+ But really 3NO3- NO3-

  9. Non Redox Reactions • 1. Both reactants are soluble in water • Mark with (aq) • 2. Must determine if products are soluble or insoluble using solubility rules • If soluble – mark with (aq) • If insoluble – mark with (s)

  10. Double Replacement Two elements in reactants take the place of each other AB + CD AD + CB AgNO3(aq)+ NaCl(aq)AgCl(s) + NaNO3(aq) Zn(OH)2(aq) + 2HCl(aq)ZnCl2(aq)+ 2H2O(l)

  11. Double Replacement • Reactants must be two ionic compounds or acids. • Usually in aqueous solution • Na2SO4(aq) + CaCl2(aq)® • The positive ions change place. • Na2SO4(aq)+ CaCl2(aq)®Ca+2SO42- + Na+1Cl-1 • Na2SO4(aq) + CaCl2(aq)® CaSO4(s) + 2NaCl(aq)

  12. To Double Replace or Not to Double Replace? That is the Question! • Will only happen if one of the products: • doesn’t dissolve in water and forms an insoluble solid (s) (precipitate). • is a gas that bubbles out. • is water (H2O) (neutralization reaction).

  13. Predicting the Precipitate • Insoluble salt = a precipitate • Solubility rules (see handout for explanation) CASH N GiAm

  14. Solubility Rules PracticePredict whether each of the following will be soluble (aq) or an insoluble ppt (s): • KCl • Na2SO4 • CaSO4 • AgSO4 • Na2CO3 • MgS

  15. Solubility Rules Practice Answers • KCl(aq) • Na2SO4(aq) • CaSO4(s) • AgSO4(s) • Na2CO3(aq) • MgS(s)

  16. Complete & Net Ionic Equations • Many reactions occur in water- that is, in aqueous solution • Many ionic compounds “dissociate”, or separate, into cations and anions when dissolved in water • Now we can write a complete ionic equation & net ionic equation.

  17. Complete Ionic Equation • Example: AgNO3(aq) + NaCl (aq) AgCl (s) + NaNO3(aq) • this is the full equation (molecular equation) 2. now write it as an complete ionic equation Anything (aq) will dissociate (separate into ions) Ag+ + NO3- + Na+ + Cl-  AgCl(s) + Na+ + NO3-

  18. Net Ionic Equation Complete ionic equation: Ag+ + NO3- + Na+ + Cl-  AgCl(s) + Na+ + NO3- 3. can be simplified by eliminating ions not directly involved in making the reaction happen (spectator ions) = net ionic equation Ag+ + Cl- AgCl(s) Na+ and NO3- are spectator ions and are removed in the net ionic equation.

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