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3.1 Reaction Stoichiometry , Limiting Reagent and % Yields (5 pts each/20 points total)

EXAM POSTPONED UNTIL MONDAY 25 NOVEMBER. All material from 23 October Powerpoints 23-36 Mini quizzes 17-23 + lab questions on: Titration Metathesis reactions Gas laws. 3.1 Reaction Stoichiometry , Limiting Reagent and % Yields (5 pts each/20 points total).

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3.1 Reaction Stoichiometry , Limiting Reagent and % Yields (5 pts each/20 points total)

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  1. EXAM POSTPONED UNTIL MONDAY 25NOVEMBER • All material from 23 October • Powerpoints 23-36 • Mini quizzes 17-23 + lab questions on: • Titration • Metathesis reactions • Gas laws 3.1 Reaction Stoichiometry, Limiting Reagent and % Yields (5 pts each/20 points total) a) How many grams of water are formed in the reaction below when 1.4074 g of C8H18 are burned with excess O2 in the balanced reaction below ? (Must show work for credit) Molecular mass 114 32 44 18 g/mol 2C8H18 + 25 O2 16CO2+ 18H2O b) Using the same balanced reaction above, predict the grams of CO2 expected if 3.409 g of O2 and 3.8863 g C8H18 are burned together. (Must show work for credit) c) Using the same balanced reaction above, compute the % yield for the reaction if 1.14 g of C8H18 in excess O2 yields 0.810 g H2O. (Must show work for credit) 3.2. Ions and Ionic Compound Prediction (14 pts total) Ionic radii ________ in size down a column The most likely ionic compound formed from K and P is:

  2. 3.3 Extended Lewis Structures , Formal Charges and VSEPR Shapes (18 pts total) Draw the best Lewis structure for the compounds below. Make sure to show all lone pairs and indicate any formal charges. (Remember that the best Lewis structure sometimes requires breaking the octet rule to minimize formal charge.) SO3 PO43- What are the shapes of the above compounds ? 3.4. Metathesis Reactions (10 Pts) a) Write the complete balanced molecular, complete ionic and net ionic equation for the reaction of silver nitrate (AgNO3) with calcium chloride (CaCl2) given that both are soluble in water and form an insoluble silver chloride precipitate. b) What are three characteristics of metathesis reactions ? 3.5 Acid-Base Reactions and models (~15 pts) Which are not Arrhenius bases, but can be Bronsted bases in the list below: CO32-HBrCl- OH‑ NH4+ Identify the base (B), acid(A), conjugate acid (CA) and conjugate base (CB) below: NH3 + HBr NH4+ + Br- 2

  3. 3.6 Titration problem (4 pts) Given a standard acid with Ca= 0.25 M, what is the concentration of an unknown base if 25.0 mL of the acid requires 20.00 mL of base to reach equivalence ? 3.7 Ideal Gas question (4 pts) You run the reaction: 2Al(s) + 6HCl(aq)  3H2(g) + 2AlCl3(aq) using 0.17 g of Al (at. wt. = 27.0 g/mol). This produces, according to the Ideal Gas equation, 9.349*10-3 mol H2. a)How many moles of H2 should you get from the reaction if it runs to completion ? b) What is your % EDA to the nearest 0.1% ? 3.8 Redox basics (10 pts) Oxidation means____ What is the oxidation # of Fe in Fe2O3 ? 3.9 Multiple choice and T/F (5 pts) The octet rule is always obeyed T F Who is the Swedish chemist ? Lewis Bronsted Arrhenius

  4. Which is not true about the Bronsted acid-base model ? • Acids are proton donors • Bases are proton acceptors • Hydrolysis produces OH- in the Bronsted model • acids + bases conjugate base + conjugate acids • None of the above

  5. Which part of the Bronsted salt Na2CO3causes hydrolysis? • Na+ • CO32- • O2- • C 4+

  6. The conjugate base in the reactionHCO3- + PO43- CO32- + HPO42-is: • HCO3- • PO43- • CO32- • HPO42- • OH-

  7. In-class reaction Jeopardy(cont.) WHAT IS… What’s my reaction type: Acid/base hydrolysis (Bronsted) K3PO4 + H2O HK2PO4 + KOH Write my products ? AgNO3(aq) + NaCl(aq) ????? AgCl(s) + NaNO3(aq) NaOH NaHCO3 K3PO4 Pick the Bronstedbase(s) Pick the Arrhenius bases NaOH NaOHHBr NaHCO3 K3PO4

  8. Practice with Bronsted model and language 1) Identify the Bronsted bases in this list: HBrNaOH Na2CO3NH4Cl K3PO4 NaCl acid base base acid base base 2) Identify the acid (A), base (B) and the conjugate acid (CA) and conjugate base (CB) in the two reactions below 1) Na2CO3 + H3PO4 NaHCO3 + NaH2PO4 B A CA CB 2) KCN + H2O HCN + KOH CA A B CB 3) What is the hydrolysis reaction that occurs with PO43- ? HPO42- + OH- PO43- + H2O

  9. OXIDATION-REDUCTION (REDOX) REACTIONSsee pages text 458-466 REDOX REACTIONS ALL INVOLVE CHANGES IN ELECTRON OWNERSHIP EXAMPLE #1: +1 0 Mgo+ 2H+ Mg2++ H2 0 +2 Mg loses 2 e- Losing is oxidation Each H+ gains 1 e- Gaining is reduction

  10. Oxidation-Reduction: Remembering which is which….. Leo-Ger Lose electrons = oxidation Gain electrons =reduction

  11. PRACTICE ASSIGNING OXIDATION # N2 O2 H2O Fe2O3 H2SO4 N=0 O=0 H=+1 O= -2 Fe=+3 O= -2 H= +1 O= -2 S=+6

  12. PRACTICE ASSIGNING OXIDATION #(cont.) 0 +1-1 +2 -1 0 Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g) Mg Which element oxidized ? Which element reduced ? H 0 +2 +6 -2 +3 +6 -2 0 2Al(s) + 3CuSO4(aq) Al2(SO4)3(aq) + 3 Cu(s) Al Which element oxidized ? Cu Which element reduced ?

  13. PRACTICE ASSIGNING OXIDATION #(cont.) 0 +1-1 +2 -1 0 Mg(s) + 2HCl(aq)  MgCl2(aq) + H2(g) Mg Which element oxidized ? Which element reduced ? H 0 +2 +6 -2 +3 +6 -2 0 2Al(s) + 3CuSO4(aq) Al2(SO4)3(aq) + 3 Cu(s) Al Which element oxidized ? Cu Which element reduced ?

  14. SPECTACULAR REDOX REACTION BEHAVIOR 1) Thermite reaction 1)assign oxidation # 0 +3 -2 0 +3 -2 2Alo(s) + Fe2O3(s)2Fe0 (liq)+Al2O3(s) 2) Who does what? Al Which element oxidized ? Which element reduced ? Fe 3)let’s see the reaction in the `flesh’

  15. SPECTACULAR REDOX REACTION BEHAVIOR (continued) Example 2: Combustion 1) Assign Oxidation # -4 +1 0 +4 -2 +1 -2 CH4 +2O2 CO2 +2H2O 2) Who does what? C Which element oxidized ? Which element reduced ? O BURN BABY, BURN

  16. SPECTACULAR REDOX REACTION BEHAVIOR (continued) 3) Decomposition redox: aka The DEATH TO skittlesreaction 0 +1 -2 +1 +7 -2 +1 -2 +4 -2 +1 -1 C12H22O11 + 8KClO311H2O + 12CO2 + 8KCl Ox Red In class demo

  17. SPECTACULAR REDOX REACTION BEHAVIOR (continued) Example 4: Combination redox 1) Assign Oxidation # 0 0 +1 -1 : 2Na + Cl2 NaCl (table salt) 2) Who does what? Which element oxidized ? Which element reduced ? 3) Let’s see it

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