Chemistry Driving Forces Overview

1. Chemistry – Mar 1, 2019 • P3 Challenge –Translate this sentence into a balanced equation including state descriptors: • If chlorine gas is bubbled through an aqueous solution of hydrosulfuric acid, solid elemental sulfur is formed within an aqueous solution of hydrochloric acid. Get out Driving Forces p1 and p3 a) and b) for a homework check

2. Chemistry – Feb 26, 2019 • Objective – • Driving forces continued • Assignment: • Finish Driving forces Worksheet 1 • Agenda • Homework Review p3 • Acids and bases • Neutralization reactions • Gas forming reactions • Identifying Driving forces • Net ionic eqns Review(time permitting)

3. 2) Formation of water: Acids and Bases • Acids are molecular compounds that dissociate to form hydrogen ions, H+. • 6 acids dissociate completely and are called strong acids. (memory item) • HClHBr HI HNO3 H2SO4 HClO4 • All acids are aqueous solutions. (aq) Strong acids get completely dissociated. • All other acids are weak acids that split into ions only a little bit. • Bases dissociate in water to form hydroxide ion, OH- • Hydroxides of alkali and alkaline earth metals are strong bases that completely dissociate.

4. 2) Formation of water: Acids and Bases • Acids react with bases to form water and an ionic salt. • Formation of water is a driving force. • Ex: HC2H3O2 (aq) + NaOH(aq)  H2O (l) + NaC2H3O2 (aq) • Net ionic equations can be found for acid base reactions too. • All acids are aqueous solutions. (aq) Strong acids get split. • Weak acids are the ONLY (aq) substance that you DO NOT SPLIT when determining a net ionic equation.

5. 3) Formation of a gas • If a gas is produced, it will be the driving force. • Acid base reactions, decomposition reactions, and combustions often form gases. • Common gases are CO, CO2, NO2, SO2, NH3, CH4 , H2S, H2, N2, O2, F2, Cl2 (memorize these) • If a product is a gas, then gas formation is a driving force. • Ex: K2CO3 (s)  K2O (s) + CO2(g)

6. 4) Transfer of electrons: Oxidation-Reduction • How to identify a redox reaction • Is there an atom that is an element on one side and in a compound on the other side? (Single Replacement reaction) • Is there an element that has a different charge ion on both sides? (Many synthesis and decomposition reactions. Also combustion.) • Transfer of electrons is a driving force. Elements are driven to complete octets. • Note: All combustion reactions are driven by electron transfer.

7. Summary of how to identify driving forces • 4 driving forces: s forms, H2O forms, g forms, e- transfer • List all that apply for a reaction to the right of each balanced reaction. • 1) Is there a solid product?  s forms • Check solubility chart • 2) Is H2O a product?  H2O forms • 3) Is a gas one of the products?  g forms • 4) Is there a free element on one side that is within a compound on the other side?  e- transfer • If all 4 questions fail, there is no driving force and you predict “no reaction”

8. Practice ID driving forces • Balance, ID type, ID driving force • _____1. _____H3PO3_____H3PO4 + _____PH3 • _____2. _____Fe2O3 + _____C _____CO + _____Fe • _____3. _____FeS + _____O2_____Fe2O3 + _____SO2 • _____4. _____NH3 + _____O2_____NO + _____H2O • _____5._____Si + _____S8_____Si2S4

9. Exit Slip - Homework • Exit Slip: Write the complete ionic equation then determine the net ionic equation for: • NiCl2(aq) + 2 KOH (aq)  Ni(OH)2 (s) + 2 KCl (aq) • What’s Due? (Pending assignments to complete.) • Finish Driving forces Worksheet 1 • What’s Next? (How to prepare for the next day) • Read p473, p286-288, p548-549, p280-282