Equilibrium Questions and Answers

A chemistry graduate student is given 125 mL of a 0 30M chloroacetic acid HCH CICO solution Chloroacetic acid is a weak acid with K 1 3 10 What mass of NaCH CICO should the student dissolve in the HCH CICO solution to turn it into a buffer with pH 3 17 You may assume that the volume of the solution doesn t change when the NaCH CICO is dissolved in it Be sure your answer has a unit symbol and round it to 2 significant digits D

10 A chemist is studying the following reaction below The reaction has an equilibrium constant of 17 M The chemist measures the concentrations of each substance to be NH3 0 80M 2 5M and H 2 3M Is the reaction at equilibrium If not which way will it shift to attain equilibrium 2NH3 g N2 g 3H2 g nd nd W21

alculate the pH and pOH of the following solutions 1 H 1 0 x 105 M Ph 5 pOH 2 H 2 5 x 10 M 3 H 1 2 x 10 4 M 4 H 3 25 x 10 4 M 5 OH 3 0 x 108 M 10 0 0075 M hydrochloric acid HC1 6 OH 7 5 x 10 M 7 OH 5 2 x 10 M 8 OH 6 0 x 10 M questions 9 and 10 calculate the pH and the pOH of the acid 9 0 050 M perchloric acid HC104 11 Calculate the H and the OH of a substance that has a pH of 5 45 12 Calculate the OH and the H of a substance that has a pOH of 9 45 13 Using Kw 1 0 x 10 14 calculate the OH if the H is 8 7 x 104 14 Using Kw 1 0 x 10 14 calculate the H if the OH is 2 4 x 10

A solution is prepared at 25 C that is initially 0 25M in dimethylamine CH3 NH bromide CH3 NH Br Calculate the pH of the solution Round your answer to 2 decimal places pH 0 X NH a weak base with K 5 4 x 104 and 0 23M in dimethylammonium C

The conjugate acid of H 20 is H3O OH H O H H O has no conjugate acid

Caffeine C8H10N4O2 aq is a weak base with a base equilibrium constant K of 4 4 x 10 5 at 25 degrees Celsius Determine the pH of a 0 65 M solution of caffeine at this temperature 6 marks

A chemical reaction that happens quickly is spontaneous and a reaction that happens slowly is non spontaneous O True O False

013 points A mixture consisting of 1 mol of H O g and 1 mol CO g is placed in a 15 L reaction vessel at 800 K At equilibrium 0 559 mol CO g is present as a result of the reaction CO g H2O g CO2 g Hz g What is Ke at 800 K

Given the following exothermic equilibrium reaction 3 H g N g 2NH3 g Using Le Chatelier s Principle which of the following changes would shift the equilibrium toward more production of NH3 O Adding heat O Increasing the volume of the container O Adding a catalyst Removing NH3

Complete the table by indicating how each change will impact the following equilibrium system over time Write increase decrease or no change 6 Marks NO2 g 2 NO g O2 g Paragraph v B I UV A Change NO NO is added NO is added O2 is removed Increase temperature AH 62 kJ NO 0

A chemistry graduate student is given 250 mL of a 0 90M nitrous acid HNO solution Nitrous acid is a weak acid with K 4 5 x 104 What mass of KNO should the student dissolve in the HNO solution to turn it into a buffer with pH 2 95 C You may assume that the volume of the solution doesn t change when the KNO is dissolved in it Be sure your answer has a unit symbol and round it to 2 significant digits 11 0x10

50 ml of a solution containing 10 3 mol of Agt is mixed with 50 ml of 0 1 M HCl solution How many moles of Ag remain in solution Ksp AgCl 1 2 10 0 O 3 10 12 O 3 10 7 O 3 108 3 10 10

019 10 0 points A 1 0 liter container is filled with 0 300 M of PC15 at 250 C The vessel is then held at a constant temperature until the reaction PC15 g PC13 g Cl g comes to equilibrium It is found that the vessel contains 0 200 moles of PC15 What is the value of the equilibrium constant for the reaction at this temperature

What mass in grams of Na S O3 is needed to dissolve 0 44 g of AgBr in a solution volume of 1 0 L given that Ksp for AgBr is 3 3 x 10 13 and K for Ag S 03 1 is 4 7 x 10 3 Your answer should include two significant figures

A chemistry graduate student is given 125 mL of a 0 20M dimethylamine CH3 NH solution Dimethylamine is a weak base with K 5 4 10 What mass of CH3 NH Cl should the student dissolve in the CH3 2NH solution to turn it into a buffer with pH 10 55 C You may assume that the volume of the solution doesn t change when the CH3 2NH Cl is dissolved in it Be sure your answer has a unit symbol and round it to 2 significant digits 1 Da x10

What is the hybridization around the central atom in CIF4 chlorine tetrafluoride

A chemistry graduate student is given 125 mL of a 0 60M pyridine C H N solution Pyridine is a weak base with K 1 7 x 10 What mass of CH NHBr should the student dissolve in the C3H N solution to turn it into a buffer with pH 5 09 C You may assume that the volume of the solution doesn t change when the C H NHBr is dissolved in it Be sure your answer has a unit symbol and round it to 2 significant digits

The Haber process is a method to produce ammonia from hydrogen and nitrogen gases The reaction is N g 3 H g 2 NH3 g If hydrogen gas is added after the reaction has reached equilibrium the reaction will O Need more information Shift to the right to produce more product O Stop All of the nitrogen gas has been used up Shift to the left to produce more reactants

rxn for the following reaction AG rxn 6C s 3H2 g C6H6 1 2C6H6 1502 g 12CO2 g 6H O l C s O g CO2 g H g O2 g H O 1 h Calculate the value of K AG 6399 kJ mol AG 394 kJ mol AG 237 kJ mol Free Energy Equilibrium 8 Consider the following reaction at 298 K 2 NO2 g N2O4 g The values of AH and AS are 58 03 kJ mol and 176 6 J K mol respectively a Calculate the value of AG

Which of the following systems is at equilibrium O A balloon filled with hydrogen and oxygen O A bottle of water you remove from an ice chest during the summer O A bottle of carbonated water just after you unscrew the cap The pencil lead with which you are answering questions on this exam

12 Using Le Chatelier s principles for the following equilibrium predict the direction that the equilibrium will shift towards the products or towards the reactants for each of the following changes by circling either products or reactants Circle neither if the change would not affect the reaction 2 points per answer 10 points total 2 Ag2CO3 s 2 H aq 2 CH aq 2AgCl s CO2 g H O l AH 47 kcal mole Decrease H O Increase in Ag2CO3 Decrease pressure Increase H Decrease temperature Reactants Products Reactants Products Reactants Products Reactants Products Reactants Products Neither Neither Neither Neither Neither

31 Calculate the H3O of each aqueous solution with the following OH a vinegar 1 0 10 M b urine 2 0 X 10 c ammonia 5 6 M 10 M 5 V 10 2 M

5 Sodium Hydroxide and Chlorine Gas are mixed and produce Sodium Chloride Sodium Hypochlorite and Water How many grams of Sodium Hypochlorite can be produced from 48 9 grams of Chlorine Gas and 54 2 grams of Sodium Hydroxide Determine the limiting reactant

Example 3 Which way will the equilibrium shift if the system temperature goes up heat is added 2 SO2 02 2 SO3 heat Solution Even though heat is not a chemical substance for the purposes of LeChatelier s Principle you can treat it as if it has physical existence Since heat is added the reaction will shift to try and use up some of the added heat In order to do this the reaction must shift to the left Note that since heat is not part of the equilibrium expression the value of Keq would change when the chemical system is heated or cooled

Example 8 The system below is already at equilibrium when a catalyst is added to the system What happens to the position of the equilibrium Does it shift right left or no change PC13 Cl PC15 Solution There will be no change in the equilibrium BOTH with emphasis on both the forward and the reverse reactions are speeded up A catalyst just gets you to equilibrium faster it doesn t affect the final position of equilibrium like changing the concentration would E E

What of HX is hydrolyzed when preparing 0 099 M HX solution pKa HX 5 92 a 7 7 b 0 029 c 9 0 d 0 35

1 Write the equilibrium expressions for the following reactions a 2 N O g O g 4 NO g b H g CO g H O g CO g c 4 HCl g O g 2 Cl g 2 H O g d 3 H g N g 2 NH3 g e H g Cl g 2HCI g f 2 SO g O g 2 SO3 g

Calculate the solubility of PbF2 in water at 25 C You ll find Kp data in the ALEKS Data tab sp Round your answer to 2 significant digits 02 x10

A precipitation reaction occurs when a solution containing a cation red spheres and a solution containing an anion green spheres are mixed The spectator ions have been omitted from the diagram for clarity Which set of reactants best represents the diagram NaCIO aq CaCl aq OKNO3 aq CuCl aq NH Br aq Pb C H O aq Li SO aq AgNO3 aq Write the net ionic equation for the reaction Include physical states net ionic equation 388 2

Calculate the solubility of PbF in water at 25 C You ll find K data in the ALEKS Data tab Round your answer to 2 significant digits C g 3

9 What is the equation for the equilibrium constant for this reaction wollol od dro CH3CO H aq C H5OH CH3CO2C2H5 aq H20 1 noiden ofbest on w w sw

Which of the following statements is true about the reaction Ca s H O Ca OH 2 aq H g heat This reaction is non spontaneous at all temperatures This reaction is spontaneous at all temperatures irreversible As this reaction proceeds to equilibrium in a closed system the pressure wi decrease This reaction is reve

Calculate the solubility at 25 C of Ni OH in pure water and in a 0 0020 M NaOH solution You ll find Kp data in the ALEKS Data tab sp Round both of your answers to 2 significant digits solubility in pure water solubility in 0 0020 M NaOH solution 0 1 00 on 0 0x0 00

A reversible reaction is not very important to the study of chemical equilibrium a reaction that can occur in both forward and reverse directions at the same time a reaction that alternates between going to the right and going to the left a reaction that goes to completion

The solubility of AgBrO3 in water at 25 C is measured to be 1 7 Use this information to calculate Kp for AgBrO3 L sp Round your answer to 2 significant digits

These equations represent precipitation reactions Rewrite them as complete ionic equations Include phase notations AgNO3 aq KCI aq KNO3 aq AgCl s complete ionic equation Ba CIO aq K SO aq BaSO s 2 KCIO aq

9 Identify and define each of the following terms using the scenario below Limiting reactant excess reactant theoretical yield SnF 2 NaCl 2 NaF SnCl The above reaction was performed in lab and produced 2 56 g of NaF This reaction was performed using 5 62 g of SnF with excess NaCl Before starting lab the student did dimensional analysis calculations to determine that the reaction should produce 3 01g NaF a What was the limiting reactant b What was the excess reactant c What was the actual yield and how do you know d What was the theoretical yield and how do you know D The equation below shows nitrogen gas reacting with hydrogen gas to form ammonia NH3 N 3 H 2 NH3 A container contains 6 molecules of N and with 12 molecules of H and they react Draw particle diagrams showing the container before and after the reaction After

B What is the pH after 25 0 mL of 0 50 mol L NaOH is added

a What does the pH scale measure b What is the range of numbers on the pH scale c Approximately where on that scale would find each of the following strong acid strong base weak acid weak base and a neutral solution d What is the pH of a solution with an H concentration of 0 025 M at 298 K What type of solution is this

At temperatures above roughly 800 C calcium carbonate decomposes Write and balance the equation for this reaction Phase symbols are optional

In which of the following systems does the tendency to maximum entropy favour the products and the tendency to minimum enthalpy favour the reactants OPCI5 g heat PCl3 g Cl g Zn OH 2 s H CO3 aq 2 H O 1 ZnCO3 aq heat H O g CO g H CO3 heat P4 s 10 Cl g heat 4 PCI5 g

A Consider a 50 0 mL solution of 0 50 mol L benzoic acid K 6 5 x 105 What is the pH of the solution

Look at each chemical equation Below the value of the equilibrium constant is given If any of these equations can be written with a single arrow then do so making sure the arrow is pointing in the proper direction a 2NO2 Cl2 2NOCI 02 K 4 6x104 b 2Cl2 2H2O 4HCl O2 K 3 2x10 14M c CH4 Cl2 CH3Cl HCl K 1 2 eidi tot eieadroquinoy sinW 1 21 memilers bas in a chemical equilibrium What about with a liquid

Question 1 There are two solutions Solution A has pH 5 0 and solution B has pH 8 0 Select all that apply Solution A is acidic 4 pts O Solution A has higher hydronium ion concentration than solution B O Solution B has higher hydroxide ion concentration than solution A Solution B is basic Solution B has lower hydronium ion concentration than solution B Question 2 4 pts

A chemistry graduate student is given 450 mL of a 0 90M acetic acid HCH3CO solution Acetic acid is a weak acid with K 1 8 10 What mass of KCH3CO should the student dissolve in the HCH3CO solution to turn it into a buffer with pH 5 21 C You may assume that the volume of the solution doesn t change when the KCH3CO is dissolved in it Be sure your answer has a unit symbol and round it to 2 significant digits 7 HADSON 10

A solution is prepared at 25 C that is initially 0 18M in nitrous acid HNO a weak acid with K 4 5 104 and 0 43 M in sodium nitrite NaNO Calculate the pH of the solution Round your answer to 2 decimal places pH 0 X S

Normal gastric juice has a pH of about 3 Assuming that normal gastric juice is primarily aqueous HCl what is the concentration of HCL in the stomach Hint convert pH to hydronium ion concentration 0 001 M HCL 0 01 M HCL 3 M HCLI 1 0 x 102 M HCL

Refer to the chemical equation below to answer this problem Note x means the concentration of x The reaction is at equilibrium If E increases through addition what is a possible result A B C C D E

K a of this equilibrium constant equation for the reaction of acetic acid HCH3CO with water 5 7 X 010

What is the Q value for this equation Which direction will the reaction shift Given CO g H O g CO g H g K 1 0 CO g 2 0 M H 9 2 0 M CO g 1 0 M H O g 1 0 M