Study Guide for exam 1 and 2
Study Guide for exam 1 and 2 CHM116
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This 16 page Study Guide was uploaded by Nikki Bee on Saturday June 13, 2015. The Study Guide belongs to CHM116 at Purdue University taught by in Spring 2015. Since its upload, it has received 96 views. For similar materials see General Chemistry 2 Lecture in Chemistry at Purdue University.
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Date Created: 06/13/15
Speed dissociation of an acid in H20 Strong Acid virtually all HCI dissociates to ions HCI Z H Cl39 Weak Acid less than 10 dissociates to ions CH3COOH 2 CH3COO39 H Speed of a reaction both complete in lt1 sec Reversible Reactions 2 N029 N2049 Brown 39 w w w a Equilibrium is reaChed Forward rxn Backward rxn at fixed temp room temp in closed system Mixture ef Beeling the Mixture HIDE and H204 mixture rewarmed 394 te reern Cha gem Temp temperature alters equilibrium concentrations Eanmnlralritm 11f lmslants arm Fr dlurzt HI Equilibrium Helm EHIQQ Equilibrium achieved i HI e Product conc 39 increases and then becomes constant at equilibrium H3 12 Reactant conc declines and then becomes constant at equilibrium I gE l ft irtingHedwig thaw3rd equilibrium 3 What is rateforward when H2 stops changing Rate kH2l2 if elementary rxn Quantitative Description of Equilibrium The Reaction Quotient Q The reaction quotient Q is a ratio of the concentrations andor pressures of the products and reactants in a reaction mixture that may or may not be at equilibrium wAXBZyC zD CMDZ Pcy X PDZ QC or if gases Qp AWBX PAW X PBX Note Q is based on the balanced equation Qc based on concentration Qp based on partial pressure of gas K in Terms of Pressure Kp KCRTA An Z coeff prod Z coeff react If the total of moles of gas do not change then An O and Kp KC A consequence of the gas law RT Partial pressure Concentration moIL The reaction quotient for a heterogeneous system Because the concentration does not change we do not include the concentration of solids pure liquids or solid liquid solvent 1 Write reaction quotients for a CaCO3s Z CaOs 0029 Op b 2 H202aq 2 2 H20l 029 oC c NH3g HClg 2 NH4CIs op Writing the Reaction Quotient for an Overall Reaction 2 EN 0 NOZP FOI N2 g 02 g 02 g coveral N2 022 For the individual steps 1 N O ZZNO C2 N012 C 2g 2g g 1 2 2 NO oz mom ch N0212 g g g NO2 02 2 2 Gel X QCZ LNBE No2 N02 N2 02 W i021 NzllOzlz 01 X 02 X 03 0mm Overall Q is product of all 0 3 Le For the sum of reactions the overall Q is the product of OS The Form of Q for a Forward and Reverse Reaction Sulfur dioxide reacts with oxygen to form sulfur trioxide 2 SO2 g 02 g Z7503 g Q f d SOBP C W SOZHOZ This reaction is reversible What is Q for the reverse reaction A 2 503 g 2 502 g 02 g Qcrev l 1 5032 Qcfwd The equilibrium expression for a reaction written in reverse is the reciprocal of that for the original reaction Meaning of Q Q is a measure of the progress of a reaction as it heads toward equilibrium Q lt K Reaction goes to right Q gt K Reaction goes to left Q K Reaction at equilibrium Q is a measure of A c B the progress of a reaction as it heads B toward equilibrium Q Q lt K Reaction goes to right C Q gt K Reaction goes to left Q K Reaction at equilibrium TA 1m Q at O O xii W 03 Q at 75 m 23 L 5quot man 0 at 21 m 075025 3 a J W ir 2 K 3 lLB 1n 2p I Time minutes Start with 100 reactant E 5 I39FU mi39i39ii39i Le Chatelier s Principle Le Chatelier s Principle When stress is applied to a system at equilibrium the position of equilibrium the concentrations or pressures shifts to remove as much of the stress as possible Stress m Add reactant Make products shift to right Add product Make reactants shift to left Remove reactant Make reactants Remove product Make products Le Chatelier s Principle in gases N2g 3 H2g gt 2NH3g 2 P NH3 Kp PNZ X P3H2 Reducing volume by 12 doubles partial pressure of each component Before any reaction 2 PNH32 22 P2NH3 Qp 2 PNZ X 2 PHZ3 24 PNZ X P3H2 14 Kp Qplt Kp Le Chatelier s Principle in gases In a gas mixture Stress Shift Increase pressure Reduce pressure Reduce pressure Increase pressure Works only for gases Number of moles of gas must change in the reaction H2 CI2 gt 2HC does not respond to a change in pressure Le Chatelier s Principle Effect of Temperature Stress Shift Increase temp Absorb energy Decrease temp Produce energy 2 N02g N204g AH 57 kJ Exotherrnic Stress Cool the reaction Shift Produce Shift to right 2 HIg H2g 12g AH 94 k Endothermic Stress Heat the reaction Shift Absorb enemy Shift to right pH amp pOH quotpquot means quottake the negative of the log of pH The negative logarithm of the hydronium ion concentration A measure of the H3O concentration in a solution pH ogH3O H3O 10 IOH antiogpH pOH A measure of the OH concentration in a solution pOH ogOH39 OH39 10 IOOH antiogpOH pKW og KW 14 pH pOH HendersonHasselbalch equation simplifies calculations of pH of a buffered solution HA H20 ltgt H3O A If A HA then pH pKa I Use to calculate ratio of acidbase needed to make buffer of given pH or amounts of each ll Use to calculate the change in pH upon addition of H or 0H
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