1 / 26

Predicting Whether a Reaction Will Occur

Predicting Whether a Reaction Will Occur. “Forces” that drive a reaction: Formation of a solid Formation of water Transfer of electrons Formation of a gas When chemicals (dissolved in water) are mixed and one of these four things can occur, the reaction will generally happen. Dissociation.

jontae
Télécharger la présentation

Predicting Whether a Reaction Will Occur

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  1. Predicting Whether a Reaction Will Occur “Forces” that drive a reaction: • Formation of a solid • Formation of water • Transfer of electrons • Formation of a gas When chemicals (dissolved in water) are mixed and one of these four things can occur, the reaction will generally happen.

  2. Dissociation • Ionic compounds • Metal + nonmetal (Type I & II) • Metal + polyatomic anion • Polyatomic cation + anion • Dissociation: When ionic compounds dissolve in water the anions and cations are separated from each other. • We know that ionic compounds dissociate when they dissolve in water because the solution conducts electricity.

  3. K Cl K+ Cl- Cu SO4 Cu+2 SO42- Dissociation (cont.) • Potassium chloride dissociates in water into potassium cations and chloride anions. KCl(aq) = K+ (aq) + Cl- (aq) • Copper(II) sulfate dissociates in water into copper(II) cations and sulfate anions. CuSO4(aq) = Cu+2(aq) + SO42-(aq)

  4. K+ Ag+ K+ Ag I I- NO3- NO3- Precipitation Reactions • In all precipitation reactions, the ions of one substance are exchanged with the ions of another substance when their aqueous solutions are mixed. • At least one of the products formed is insoluble in water. KI(aq) + AgNO3(aq) KNO3(aq) + AgIs

  5. Process for Predicting the Products of a Precipitation Reaction • Determine what ions each aqueous reactant has. • Exchange ions. • (+) ion from one reactant with (-) ion from other • Balance charges of combined ions to get formulaof each product. • Balance the equation. • Count atoms. • Determine solubility of each product in water. • Use solubility rules. • If product is insoluble or slightly soluble, it will precipitate.

  6. Solubility Rules • Most compounds that contain NO3- ions are soluble. • Most compounds that contain Na+, K+, or NH4+ ions are soluble. • Most compounds that contain Cl- ions are soluble, except AgCl, PbCl2, and Hg2Cl2 • Most compounds that contain SO42- ions are soluble, except BaSO4, PbSO4, CaSO4

  7. Solubility Rules (cont.) • Most compounds that contain OH- ions are slightly soluble (will precipitate), except NaOH and KOH, which are soluble, and Ba(OH)2, Ca(OH)2, which are moderately soluble. • Most compounds that contain S2-, CO32-, or PO43- ions are slightly soluble (will precipitate).

  8. Predict what will happen when the following solutions are mixed: • AgNO3(aq) and NH4Cl(aq) • Na3PO4(aq) and Co(NO2)2(aq) • K2CrO4(aq) and Pb(C2H3O2)2(aq)

  9. Describing Reactions in Aqueous Solutions • Molecular equations: equations that show the complete formulas of all reactants and products Example: • Ionic equations: All substances that are strong electrolytes are represented as ions. Solids are not written as separate ions. Example:

  10. Describing Reactions in Aqueous Solutions (cont.) • Spectator ions: ions that do not participate in the reaction Example: • Net ionic equation: Only the components directly involved the reaction are written. Example:

  11. Write molecular, complete ionic, and net ionic equations for the following reaction: • nickel(II) sulfate and barium chloride

  12. Write molecular, complete ionic, and net ionic equations for the following reaction: • iron(III) nitrate and sodium hydroxide

  13. Reactions that Form Water: Acids and Bases • When acids dissociate in water they release H+ ions and their anions. • When bases dissociate in water they release or form OH- ions and their cations.

  14. Acid-Base Reactions • In the reaction of an acid with a base, the H+ from the acid combines with the OH- from the base to make water. • The cation from the base combines with the anion from the acid to make the salt. acid + base salt + water H2SO4(aq) + Ca(OH)2(aq)  CaSO4(aq) + 2 H2O(l) • The net ionic equation for a strong acid-strong base reaction is always: H+ (aq) + OH- (aq)  H2O(l)

  15. Erucic Acid (a weak acid from marsh marigold)

  16. Complete the following acid-base reactions: HCl(aq) + RbOH(aq) → HNO3(aq) + LiOH(aq) →

  17. Oxidation-Reduction Reactions • Oxidation-reduction reactions: reactions that involve a transfer of one or more electrons • The substance that loses electrons in the reaction is oxidized. The substance that gains electrons in the reaction is reduced.

  18. Reactions of Metals withNonmetals (Oxidation-Reduction) • The metal loses electrons and becomes a cation (oxidation) • The nonmetal gains electrons and becomes an anion (reduction) • In the reaction, electrons are transferred from the metal to the nonmetal. 2K(s) + F2(g) → 2KF(s) metal nonmetal

  19. Characteristics of Oxidation-Reduction Reactions • Metal + nonmetal  ionic compound (solid) • In the ionic compound the metal is now a cation and the nonmetal is an anion. • Two nonmetals can undergo an oxidation-reduction reaction. Look for O2 as a reactant or product. In this case the products are not ionic. • Examples:

  20. Ways to Classify Reactions • Precipitation reactions: reactions that involve solid formation. Example: • Double displacement reactions: ion exchange reactions AB + CD → AD + CB Example: • Acid-base reactions: reactions that involve water formation Example: • Both precipitation reactions and acid-base reactions involve compounds exchanging ions.

  21. Ways to Classify Reactions (cont.) • Oxidation-reduction reactions: reactions that involve electron transfer Example: Also classified as a single displacement reaction: A + BC → B + AC • Combustion reactions: reactions in which O2(g) is reacted with a carbon compound • Release a lot of energy • Subclass of oxidation-reduction reactions • Example:

  22. Other Ways to Classify Reactions • Synthesis reactions: reactions in which chemicals combine to make one product • Metal + nonmetal reactions can be classified as synthesis reactions. Example: • Reactions of metals or monmetals with O2 can be classified as synthesis reactions. Example: • These two types of synthesis reactions are also subclasses of oxidation-reduction reactions.

  23. Other Ways to Classify Reactions • Decomposition reactions: reactions in which one reactant breaks down into simpler compounds or elements • Generally initiated by addition of electric current or heat Example: • Opposite of a synthesis reaction

  24. Summary of Classes of Reactions

  25. Classify the following reactions in as many ways as possible: C(s) + O2(g) → CO2(g) Zn(s) + 2HBr(aq) → H2(g) + ZnBr(aq) 2KClO3(s) → 2KCl(s) + 3O2(g) H2SO4(aq) + Ba(OH)2(aq) → 2H2O(l) + BaSO4(s)

More Related