Equilibrium Questions and Answers

4 A 1 00 L buffer solution is 0 250 M in HF and 0 250 M in NaF Calculate the pH of the solution after the addition of 100 0 mL of 1 00 M HCl The Ka for HF is 3 5 10 4 f x 1000 or A HF 0 950M 1000ml 100 06 n

pH log H3O H3O 1 10 PH OH 10 POH pOH log OH pH pOH 14 H3O OH 10 14 What will be the pH if 0 00150 moles of HCI is added to 1 00 L of water The reaction gives the conversion factor HCl H O H30 CI 1 A 1 5000 B 2 5223 OC 2 824 D 3 125 OFG502 start 0 00150 equil 0 0 0

Exercise N Identifying buffer solutions State whether each of the following solutions represents a buffer system and explain why or why not H SO4 and K2SO4 Na3PO4 and H3PO4 H CO3 and NaHCO3 M MPC

Dalton s Law of Partial Pressures In a thermochemical experiment ammonia undergoes decomposition to nitrogen and hydrogen At the end of the experiment the pressure of the gas mixture is 966 mmHg Calculate the partial pressures of N2 and H in mmHg and in atm Show your calculations And give your answer in 3 significant figures

4 points Consider a mixture of 1 01 M HCIO and 2 35 M NaCIO Given that the K for HCIO 2 9 x 10 8 determine the pH of this solution Report your answer with two places past the decimal point

15 What is the concentration of hydroxide ions OH AND the pOH of an aqueous solution i the molar concentration of hydronium ions H3O is 7 90 x 108 M POH log OH log H o

16 What volume of 0 110 M NaOH in mL must be added to reach the equivalence point of a 250 mL solution containing 0 0428 g of carbonic acid H CO3 a diprotic acid 0 110 Mole NaOH 250 63 mok 103 not IMMole 03 2 SOX 10 MOL 0 410 2 172 2 27X163 ML

2 sp Determine the molar solubility of PbCl2 Hint Write the ICE table and Ksp expression out and be careful of exponents Report your answer with 4 places past the decimal point Do not use scientific notation

Which of the following is the conjugate acid of carbonic acid HCO3 a H3CO3 b H CO3 9 CO32 d H O A species that can act as either an acid or base depending on reaction con a Polyprotic h Bascid

19 The equilibrium constant K for the unbalance reaction below is 41 At equilibrium the concentrations of NO 0 60 M and NoBr 0 0985 M What is the concentration of Br at Base acid equilibrium 2 NOBr g 2 NO g Br2 g no brac 197 147 K 2N0 1 20 C 230 AGAFAS K NO B NoBr

3 points Determine the equilibrium constant Kc for the following process 2A B 2C Aleq 0 0601 B eq 0 0369 Cleq 0 1383 Report your answer with 1 place past the decimal point Type your answer

Reaction HCl aq NaOH aq NaCl aq H O What is the final pH if 6 00 L of 0 0200 M HCl is placed in a beaker with 1 80 L of 0 100 M NaOH answer pH 11 89 a Convert given HCl data to moles b Convert given NaOH data to moles c Subtract the lesser amount from parts a and b from the greater amount This is the amount of excess d Add volumes of both solutions to determine total volume e Divide excess moles from part c by total volume from part d this is either H or OH depending on whether acid or base was in excess Determine pH using appropriate math equations P

10 5 Calculate the pH for the solutions which have the following H3O 9 5 x 10 7 7 9 x 10 3 4 4 x 10 10

2 points Consider the following equilibrium 2CO2 2C0 0 The equilibrium constant Kc for this process is 0 00000057 If the initial concentration of CO is 0 0016M what is the equilibrium concentration of CO in M HINT Write out the ICE table and write the expression for the equilibrium constant Be careful with exponents Be sure to solve for the concentration of CC You do not need to use the quadratic formula Do not report units in your answer Report your answer with 6 places past the decimal point Do not use scientific notation Type your answer

If the reaction quotient for a reaction is larger than the equilibrium constant i e Qc Kc then the reaction Is at equilibrium Must shift from left to right to reach equilibrium Will always proceed to equilibrium very rapidly Must shift from right to left to reach equilibrium

Consider the exothermic equilibrium CO g 2H 8 CH3OH g Answer the following questions 01 56 44 Time Remaining 5 Shifts to the left reactants Shifts to the right products Does not change 2 points If H is removed in the equilibrium mixture the equilibrium position Shifts to the left reactants Shifts to the right products Does not change 000 6 2 points If a catalyst is added the equilibrium position Does not change Shifts to the left reactants Shifts to the right products 7 Submit 2 points If the equilibrium mixture is cooled the equilibrium position Does not change Shifts to the right products

A 29 9 mL sample of 0 150 M formic acid HCHO2 is titrated with 0 150 M NaOH Calculate the pH after the addition of 29 9 mL of NaOF For HCHO K 1 76 10 4 Hint Determine the equivalence point so you know where you are in the titration Report your answer with 2 places past the decimal point

onsider the following reaction CO g 3H g CH4 g H O g AH 74 85 kJ mol dicate how equilibrium will be affected by circling the correct response if a CH4 g is added shift left shift right b H O g is removed shift left shift right shift left shift right e Pressure is increased shift left shift right d Temperature is increased no change no change no change no change

Le Chatelier s Principle Consider the exothermic equilibrium CO g 2H g CH3OH g Answer the following questions 4 5 2 points If extra CO is added to the equilibrium mixture the equilibrium position Shifts to the left reactants Shifts to the right products Does not change 2 points If H is removed in the equilibrium mixture the equilibrium position Shifts to the left reactants Shifts to the right products Does not change OO

Which is not true i e false of a reaction quotient Q The formula is the same as the equilibrium constant It tells you whether or not the system can or cannot reach equilibrium It can predict the direction in which the reaction shifts to reach equilibrium It has a numerical value

H g 2 NO g N O g H O g Kc 2 3 x 106 at a certain temperature If the closed system contains H 0 050 mol L NO 0 020 mol L N O 5 4 mol L and H O 8 7 mol L then we can accurately predict that These questions are laughable get it Laughing gas This system is far from equilibrium and will shift to the left to achieve equilibrium The reaction is at equilibrium This system is far from equilibrium and will shift to the right to achieve

Reaction HCIO aq KOH aq KCIO aq H O l What is the final pH if 0 503 L of 0 622 M HCIO is placed in a beaker with 0 0982 L of 1 077 M KOH answer pH 0 463 WHER

2 Circle ALL statements that would NOT affect the rate of this reaction a The addition of a catalyst B The temperature of the reactants c The concentration of products C and D e The concentration of reactants A and B The surface area of the reactants f The physical state of the reactants g The entropy of the reaction

The reaction 2 SO2 g O2 g 2 SO3 g is at equilibrium at 543K Before the reaction the concentrations of the gases were SO 0 060 mol L 0 0 050 mol L and SO3 0 00 mol L At equilibrium SO3 0 040 mol L What are the K and the Kp values R 0 08206 atm L mol K OK 13 3 K 0 325 OKc4 0 Kp 0 090 Ke 133 K 2 98 K 8 88 K 0 200

6 Identify a good buffer small amounts of both a weak acid and its conjugate base b significant amounts of both a strong acid and a strong base C significant amounts of both a weak acid and a strong acid d significant amounts of both a weak acid and its conjugate base 7 Which of the following is the conjugate base of HPO4 H3PO4 b H PO4 c OH e 3 PO4

For the system 2 HI g H g 12 g at 445 C the value for K is 0 020 A mixture of H2 I2 and HI in a vessel at 445 C has the following concentrations HI 2 0 mol L H 0 50 mol L and 12 0 10 mol L Which one of the following statements about Qc is TRUE for the above system Qc is greater than Ke more H and 12 will form Qc is less than Kc more HI will form OQ is less than Ke so more H 12 will form Qc Kc the system is at equilibrium

A reaction quotient is calculated to be 3 2 x 10 5 The equilibrium constant for the same reaction is 5 4 x 10 5 Which statement is correct The system is at equilibrium The system will reach equilibrium by moving to the left The system will reach equilibrium by moving to the right The concentrations of the products are greater than their concentrations at equilibrium

Ime Remaining When a chemical reaction is at equilibrium the concentrations of reactants and products do not change over time This is because the rate in th forward direction becomes equal to the rate in the reverse reaction Note that the rates are not zero So if more reactant is added the forward rates increases and more product is made If more product is added the reverse rate increases and more reactant is made Adding or removing reactant or product is called a stress The chemical reaction responds to the stress in such a way to minimize the stress as the reaction goes to a new point of equilibrium This is called Le Chatelier s Principle We ll use the following exothermic reaction where all are in the gaseous phase 2 NO 0 2 NO 114 kJ mol NO is added the NO will increase For example when result 2 NO 0 2 NO 114 kJ mol stress NO This can also be seen in the constant Keq which must remain a constant Keq NO 0 To reduce the effect of added NO NO will increase and 0 will decrease Answer the following questions about the reaction at equilibrium 2 NO 114 kJ mol 2 NO 0 What happens to the NO when NO is added What happens to the NO when NO is removed What happens to the NO when O is added What happens to the NO when O is removed

Which of the following statements must be true for the entropy of a pure solid to be zero 1 The temperature must be 0 K 2 The solid must be crystalline not amorphous 3 The solid must be perfectly ordered 4 The solid must be an element 01 O 1 2 3 and 4 O1 and 2 1 2 and 3

The Keq for the reaction of water with water is called Kw H O H O H30 OH H3O OH Kw H 0 OH 1 x 10 7 1 x 10 14 H O The inverse logarithm or log of H3O OH 10 14 is pH pOH 14 1 What happens to the H30 when acid is added to neutral water the H30 goes 2 What happens to the pH when acid is added to neutral water an example of an increased H3O is H30 1 x 106 Thus pH log 106 6 thus adding acid makes the pH go 3 What happens to the OH when acid is added to neutral water in the equation H O OH 10 14 when H30 increases the OH goes 4 What happens to the pOH when acid is added to neutral water when OH decreases the pOH goes this can also be seen using pH pOH 14 5 What happens to the Kw when acid is added to neutral water since the pOH log OH

Heat is treated as any other reactant or product We also saw this in stoichometry Answer the following questions about the reaction at equilibrium 2 NO 0 2 NO 114 kJ mol What happens to the NO when heat is added What happens to the NO when heat is removed The reaction would respond to an increase in pressure by trying to reduce this stress With gases the pressure is related to moles by PV Thus reducing the moles at equilibrium will reduce the pressure Which side of the reaction has the most moles reactants or products What happens to the NO when the pressure is increased What happens to the NO when the pressure is decreased A increases B decreases C no change D reactants E products

The following is list of weak acids and their pk values weak acid benzoic acid hydrogen citrate 6 40 hydrocyanic acid 9 31 hydrogen phosphate 12 38 Which would be the best buffer to use at pH 7 at pH 7 For benzoic acid a 50 50 mixture of benzoic acid and its conjugate base the benzoate lon would have pH The buffering capacity of a benzoic acid benzoate buffer would be A 4 20 86 40 C 9 31 D 12 38 E benzoic acid H hydros acid DK 4 20 osphate I good F hydrogen citrate I had

For the following reaction at equilibrium NH3 H O NH OH K 1 K is a constant What happens to the NH3 if some base is added and the OH increases What happens to the NH3 if some acid is added and the OH decreases a NH3 b H O C NH T d OH e increases f decreases

Consider the reaction 2Na s 2H O 1 2NaOH aq H g Using standard thermodynamic data at 298K calculate the free energy change when 2 46 moles of Na s rea standard conditions AG rxn KJ

Without doing any calculations determine whether the standard entropy change AS is positive or negative for each of the following reactions AS 0 for reaction 1 AS 0 for both reactions AS 0 for both reactions OASO A for manction 2 Reaction 1 C graphite O g CO g Reaction 2 2 CO g O g 2 CO g AS 0 for reaction 2 ASO 0 for reaction 1

start 0 050 M equil 0 045 M 0 005 M The amount of CH3NH that was converted into product was 0 050 M 0 045 M For each 1 or 0 005 M CH3NH X 0 005 M CH3NH2 1 mol CH3NH Keg 1 mol CH3NH2 1 mol OH 1 mol CH3NH CH3NH3 OH 0 of CH3NH converted into products there will be 0 005 M of CH NH3 and CH NH3 OH 1 of OH

Answer each of the following for the following reaction H SO3 H O HSO3 H 0 For polyprotic acids only one acidic hydrogen is removed by a very weak base such as water is the acid is the base is the conjugate acid is the conjugate base H SO3 is not on the list of seven strong acid so is treated like a a H SO3 b H C H30 d HSO3 e SO3 g strong h weak f H O h acid and we use a double sided arrow

When a weak acid dissolves in water it doesn t completely ionize dissociate but goes to equilibrium At equilibrium the rate in the forward direction is equal to the rate in the reverse reaction thus the concentrations no longer change When the concentrations are constant the ratio of the concentrations are also constant and this is called the equilibrium constant For the weak acid HF dissolving in water the Keq is defined as HF H O F H 0 products reactants A HF B H O C F D H 0

equil 0 030 M 0 020 M The amount of HF that was converted into products was 0 050 M 0 030 M For each 0 020 M HFX 0 020 M HFX Keg 1 mol F1 1 mol HF 1 mol H 0 1 1 mol HF F H0 of HF converted into products there will be 0 020 M of F and H30 1 of H30 or

A similar treatment can be used with weak bases The Keq can then be called K When a weak base dissolves in water it doesn t completely ionize dissociate but goes to equilibrium At equilibrium the rate in the forward direction is equal to the rate in the reverse reaction thus the concentrations no longer change When the concentrations are constant the ratio of the concentrations are also constant and this is called the equilibrium constant For the weak base CH3NH treat just like ammonia NH3 dissolving in water the Keq is defined as CH3NH H O CH3NH OH products Kb reactants A HF B H O C F D H 0 CH NH 2 F CH3NH G OH

Al OH 3 has an OH in the formula so we don t use water in the reaction because it just cancels out Al OH 3 H O Al3 3 OH H O Answer each of the following for the following reaction Al OH 3 Al 3OH Al OH 3 has an OH in the formula so is treated like a There is no acid or conjugate acid a Al 3 g none is the acid is the base is the conjugate acid is the conjugate base d NH4 b H C H30 1 h strong i weak e OH f H O base and we should use a one sided arrow

Answer each of the following for the following reaction HCI H O CI H 0 HCI is a a HCI b H is the acid is the base is the conjugate acid is the conjugate base 6 H 0 1 acid so we use the one directional arrow dc1 f strong ST work

of it req 75 0mL of 0 500M NaOH to neutralize 165 0mL of an HCI soln what is the concentration of the HCI soln

Chemist dissolves 849 mg of pure hydroiodic acid in enough water to make up 250 mL of solution Calculate the pH of the solution Round your answer gnificant decimal places 11

5 0 500 M hypochlorous acid HCLO a weak acid K 3 5 10 8 M 2

ch Substance Lewis base Bronsted Lowry base Arrhenius base Definition A Provides H in water B Provides OH in water C Proton donor D Proton acceptor E Electron pair donor F Electron pair acceptor

When 35 0 mL of 0 400 M hydrochloric acid and 35 0 mL of 0 400 M ammonia are combined the pH of the resulting solution will be A Less than 7 B Equal to 7 C Greater than 7

emist dissolves 271 mg of pure hydrobromic acid in enough water to make up 120 mL of solution Calculate the pH of the solution Round your swer to significant decimal places X C C

The following is the data obtained from noaa gov a website for the National Oceanic and atmospheric Administration NOAA Hawaii Carbon Dioxide Time Series 425 400 375 350 325 300 275 CO2 Time Series in the North Pacific Mauna Loa Atmospheric CO ppm ALOHA seawater pCO2 insitu uatm ALOHA seawater pH insitu 160 W 158 W 156 W Station ALOHA Station Mauna Loa 1967 23 N 22 21 20 19 1985 Relevant chemical equation and formula CO2 H O 6 H CO30 H HCO3 pH log H Year 2003 1958 2012 1976 1994 Data Mauna Loa ftp aftp cmdl noaa gov products trends co2 co2 mm mlo txt ALOHA http hahana soest hawaii edu hot hot dogs bextraction html ALOHA pH PCO are calculated at in situ temperature from DIC TA measured from samples collected on Hawaii Ocean Times series HOT cruises using co2sys Pelletier v25b06 with constants Lueker et al 2000 KSO4 Dickson Total boron Lee et al 2010 KF seacarb Please answer the following questions based on the information provided above 8 30 2021 8 25 1 What problem in the oceans does the data collected from 1985 to 2021 show 8 20 8 15 8 10 8 05 8 00 2 One of the points in article published by Patrick Moore says oceans built in buffer stops pH swinging Do you agree with that Explain

Temperature C Part B Use the graph below to answer the questions that follow 180 160 140 120 100 80 60 40 2 Phase Change Diagram B 4 A 6 8 D 10 12 14 16 18 Time minutes E 20 6 What phase change is occurring between point B to C Is this endothermic or exothermic What are the molecules doing for this change to occur 7 What phase change is occurring between point 22 E to D Is this endothermic or exothermic What are the molecules doing for this change to occur MU 8 The portion labeled CD shows a change in what type of energy Kinetic or potential 9 What is the phase change called when a substance goes from a solid directly to a gas s g 10 As the diagram goes from A to E what is happening to the kinetic energy What happens to the molecules as you go from A to E