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Reactions day one

Reactions day one. Three types: Precipitation Acid & base Redox. Reactions in Solution (or precipitation reactions). What we need to know Dissolving Molarity Solubility rules Use to predict if reaction occurs Predicting products of reactions Net ionic equations. Dissolving.

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Reactions day one

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  1. Reactions day one Three types: Precipitation Acid & base Redox

  2. Reactions in Solution (or precipitation reactions) • What we need to know • Dissolving • Molarity • Solubility rules • Use to predict if reaction occurs • Predicting products of reactions • Net ionic equations

  3. Dissolving • How water dissolves substances • Check out this clip

  4. Molarity • A measure of concentration of solute in a solution • Has units of moles solute/ L of solution • Equations • M = mole/V • Usually mass to solution or in stoich • M1 V1 = M2 V2 • This is for a dilution of an exiting solution

  5. Molarity • A volume of 15 mL of 0.50 M NaCl is measured out for a lab. What is the mass of NaCl present in this sample? • 0.44g NaCl • What is the molarity of a solution that is prepared by diluting 8.3mL of 12 M HCl to a volume of 1000.0 mL? • 0.10M HCl

  6. Solubility Rules • The ugly truth • The up side • Until the test have the guide handy but wean yourself from it before the test • Check p. 145 for different presentation of rules

  7. Predicting precip. products • Usually ionic compounds • Like a dysfunctional couples dance • AX + BZ → AZ + BX • After determining products check states • If there is a solid or gas formed, the reaction occurs • If everything is still aqueous, there is no reaction and NR should be written in place of products

  8. Predicting precip. products • Try these: • AgNO3 (aq)+ CuCl2 (aq) • K2CrO4 (aq) + Ba(CH3CO2)2 (aq) • NH4Cl (aq) + Na3PO4 (aq) • Answers: • AgCl(s) + Cu(NO3)2 (aq) • BaCrO4 (s) + KCH3CO2 (aq) • NR

  9. Net Ionic equations • Shows only the substances that are involved in chemical changes • Spectator ions (ions that are unchanged in the reaction) are left out

  10. Net Ionics • The long way: • KI (aq) + Pb(NO3)2 (aq)→ KNO3 (aq) + PbI2 (s) • Show all dissolved compounds as ions • K1+ + I1- + Pb2+ + NO31-→ K1+ +NO31- + PbI2 • Cross out what is not changed • K1+ + I1- + Pb2+ + NO31-→ K1+ +NO31- + PbI2 • Net ionic is the stuff left over, write it out • I1- + Pb2+ → PbI2 (s)

  11. Net Ionics • The short way: • AgNO3(aq) + NaCl(aq)→ AgCl(s) + NaNO3(aq) • Take the non-aqueous as a product and then determine the reactants used to form them • Ag1+ + Cl1-→ AgCl(s)

  12. HW • Ch. 4: #8 (a-c), 9 (a,b), 12 (a,b), 19-23, 26

  13. Acid-Base reactions • What we need to know: • What are they? • How to write products • Ratios for neutralization

  14. What are they? • Definitions vary in specificity but… • Acids typically contain H atoms that will break off (dissociate) in solution • Bases typically contain OH ions that will dissociate • Both can vary in strength depending on amount of H+ or OH- that forms in solution

  15. What are they? • Common acids: • HCl, H2SO4, HBr, CH3COOH, see your poly sheet for more… yep you need to know them • Common bases: • NaOH, Ca(OH)2, Mg(OH)2, KOH, get the picture?

  16. How to write products • Does this look familiar? • AX + BZ → AZ + BX • Try one • Mg(OH)2 (aq) + HI (aq)→ • MgI2(aq) + H2O(l) • One of the products will (almost) always be there in an acid base reaction, which one?

  17. Neutralization • When moles of H+ = moles of OH- • Need a balanced equation • Basically it is stoich along with molarity… yea!

  18. Neutralization • What amount of moles of HCl is needed to neutralize 5 moles of Mg(OH)2? • Mg(OH)2 (aq) + 2 HCl (aq)→ MgCl2(aq) + 2 H2O(l) • 5 moles Mg(OH)2 x (2 mol HCl / 1 mol Mg(OH)2) = 10 moles HCl • What if the problem were… What volume of 1.0M HCl is rq’d to neutralize 50.0 mL of 0.10M Mg(OH)2 (aq)? • Answer: 0.010 L or 10. mL of HCl

  19. HW • Ch. 4 p. 176 #31, 32, 35, 36 • Introduction to Red-Ox reactions • Read 157 – 163 • Answer questions #41 (a-e), 42 (a-e) and 43 • Should be able to: • Assign oxidation states • Know definition of: • Oxidation, reduction, oxidizing agent, reducing agent

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