1 / 27

Test 2 Study Guide

Test 2 Study Guide. Thursday February 28 8:00 p.m. Dobo 134. Top 7 Topics. Limiting reactants Ionic compounds in water Molarity Energy Specific heat Enthalpy Hess’ Law. Limiting Reactants - 3. Theoretical Yield How much is used, formed, left over. Ionic Compounds 5. In water

tgirton
Télécharger la présentation

Test 2 Study Guide

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. Test 2 Study Guide Thursday February 28 8:00 p.m. Dobo 134

  2. Top 7 Topics • Limiting reactants • Ionic compounds in water • Molarity • Energy • Specific heat • Enthalpy • Hess’ Law

  3. Limiting Reactants - 3 • Theoretical Yield • How much is used, formed, left over

  4. Ionic Compounds 5 • In water • Strong / weak electrolytes • Ionic equations • Metathesis reactions • Ion Solubility

  5. Molarity 4 • Interconverting molarity, moles, volume • Dilution

  6. Energy 2 • E = q + w

  7. Specific heat 1 • Calculate energy given specific heat

  8. Enthalpy 3 • Endo , exo, sign of H • Given heat for a certain mass, calculate reaction H • Given H and mass, calculate heat

  9. Hess’ Law 2 • Addition of reactions to obtain H

  10. Top 7 TopicsLet’s do some examples! • Limiting reactants • Ionic compounds in water • Molarity • Energy • Specific heat • Enthalpy • Hess’ Law

  11. Limiting Reactants - 3 • Theoretical Yield – how much you expect based upon the amount of reactants. • If one reactant is is present in excess, then the other limits how much can be made and is used to determine the theoretical yield.

  12. 2H2 + O2 2 H2O • If 10 moles of oxygen and 10 moles of hydrogen…. • The hydrogen limits the amount of water that can be formed • Based upon 10 moles H2, we can make 10 moles water • Based upon 10 moles O2, we can make 20 moles water. • H2 limits. Theoretical Yield = 10 moles ( 180 g) H2O • At end of reaction, will have 5 moles O2 left over

  13. How much is used, formed, left over • Q 1 on Test

  14. Ionic Compounds 5 • In water • Strong / weak electrolytes • Ionic equations • Metathesis reactions • Ion Solubility

  15. Group 1A ( alkali metals) cations soluble • NH4+ soluble • NO3- soluble • CH3CO2- = C2H3O2- = acetate soluble • Will be given a chart for other ions

  16. Soluble ionic compounds in water exist as free ions surrounded by water molecules. • Soluble ionic compounds are strong electrolytes • Strong acids or bases (HCl, H2SO4), NaOH) are strong electrolytes • Weak acids or bases (CH3CO2H, acetic acid) are weak electrolytes • Molecules that do not disassociate (CO2, sugar) are non electrolytes.

  17. potassium sulfate with barium nitrate • 2K+(aq) + SO4-2 (aq) + Ba+2 (aq) + 2 NO3- (aq) 2K+(aq) + 2 NO3- (aq) +BaSO4(s) • SO4-2 (aq) + Ba+2 (aq)  BaSO4(s)

  18. Molarity 4 • Interconverting molarity, moles, volume • M means moles per liter = moles/L • M = moles/L • If you know two things, can determine the third • If you have moles and volume, can determine molarity • 3 moles dissolved in 0.5 L = 3moles/0.5L = 6M

  19. Molarity - dilution • (Vconc )(Mconc ) = (Vdil )(Mdil ) • If you know 3, can solve for the fourth • How many mL of 3M HCl is needed to make 100mL of 1.5 M HCl? • (Vconc)(3M) = (100mL)(1.5M) • Vconc = 50 mL

  20. E = q + w • q > 0 heat transferred from the surroundings to the system (endothermic) • q < 0 heat transferred from the system to the surroundings ( exothermic) • w > 0 work is done by the surroundings on the system • w < 0 work is done by the system on the surroundings • q > 0, w > 0 E > 0 • q < 0, w < 0 E< 0

  21. Specific heat • Calculate heat energy given specific heat • q = (specific heat) ( mass in grams)(T)

  22. 18.      When 72 g of a metal at 97.0 C is added to 100.0 g of water at 25.0 C, the final temperature is 29.1 C. What is the heat capacity of the metal if cwater = 4.184 J/g.K? • Heat lost by metal = heat gained by water • qmetal = - qwater

  23. Enthalpy • Endothermic H > 0 • Exothermic H < 0

  24. Given heat for a certain mass, calculate reaction H • If it takes 60 kJ to melt 180 grams of ice, what is H for the following reaction? • H2O(s) H2O(l) • (60kJ / 180g) ( 18 g/mole) = 6 kJ/mole H = 6kJ

  25. Given H and mass, calculate heat H2O(s) H2O(l) H = 6 kJ How much heat is needed to melt 900 grams of ice? (900g)(6 kJ/mole)(1mole/18 g) = 300 kJ

  26. Hess’ Law • If a reaction is carried out in a series of steps, H for the reaction will be equal to the sum of the enthalpy changes for the individual steps.

  27. 19.      What is the value of H for IF5(g)  IF3(g) + F2(g) H = ? given the following thermochemical equations? IF(g) + F2(g)  IF3(g) H = -390 kJ IF(g) + 2 F2(g)  IF5(g) H = -745 kJ

More Related