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For a reaction at equilibrium, which change can increase the rates of the forward and reverse reactions?*
Which term identifies a factor that will shift a chemical equilibrium?*
Given the equation representing a system at equilibrium:
When the concentration of Cl−(aq) is increased, the concentration of Ag+(aq)*
Given the equation representing a reaction at equilibrium:
2SO2(g) + O2(g) ⇌ 2SO3(g) + heat
Which change causes the equilibrium to shift to the right?*
Which change causes the equilibrium to shift?*
Given the equation representing a chemical reaction at equilibrium in a sealed, rigid container:
H2(g) + I2(g) + energy ⇌ 2HI(g)
When the concentration of H2(g) is increased by adding more hydrogen gas to the container at constant temperature, the equilibrium shifts*
PCl5(g) + energy ⇌ PCl3(g) + Cl2(g)
Which change will cause the equilibrium to shift to the right?*
Base your answers to questions 8 on the information below.
Several steps are involved in the industrial production of sulfuric acid. One step involves the oxidation of sulfur dioxide gas to form sulfur trioxide gas. A catalyst is used to increase the rate of production of sulfur trioxide gas. In a rigid cylinder with a movable piston, this reaction reaches equilibrium, as represented by the equation below.
2SO2(g) + O2(g) ⇌ 2SO3(g) + 392 kJ
State, in terms of the concentration of SO3(g), what occurs when more O2(g) is added to the reaction at equilibrium.*
Base your answers to questions 9 on the information below and on your knowledge of chemistry.
Common household bleach is an aqueous solution containing hypochlorite ions. A closed container of bleach is an equilibrium system represented by the equation below.
Cl2(g) + 2OH−(aq) ⇌ ClO−(aq) + Cl−(aq) + H2O(ℓ)
Explain why the container must be closed to maintain equilibrium.*
Base your answers to questions 10 on the information below and on your knowledge of chemistry.
A student makes an aqueous solution of lactic acid. A formula for one form of lactic acid is shown below.
The solution is placed in a sealed flask to be used in a laboratory investigation. The equation below represents the lactic acid equilibrium system in the flask.
Explain, in terms of LeChatelier’s principle, why increasing the concentration of H+(aq) increases the concentration of lactic acid.*
Base your answers to questions 11 on the information below and on your knowledge of chemistry.
Nitrogen dioxide, NO2, is a dark brown gas that is used to make nitric acid and to bleach flour. Nitrogen dioxide has a boiling point of 294 K at 101.3 kPa. In a rigid cylinder with a movable piston, nitrogen dioxide can be in equilibrium with colorless dinitrogen tetroxide, N2O4. This equilibrium is represented by the equation below.
2NO2(g) ⇌ N2O4(g) + 58 kJ
State one stress, other than adding or removing NO2(g) or N2O4(g), that would increase the amount of the dark brown gas.*
Base your answers to questions 12 on the information below and on your knowledge of chemistry.
The balanced equation below represents the reaction between a 5.0-gram sample of zinc metal and a 0.5 M solution of hydrochloric acid. The reaction takes place in an open test tube at 298 K and 1 atm in a laboratory activity.
Zn(s) + 2HCl(aq) → H2(g) + ZnCl2(aq) + energy
Explain why this reaction will not reach equilibrium.*
Base your answers to questions 13 on the information below and on your knowledge of chemistry.
In a laboratory apparatus, a sample of lead(II) oxide reacts with hydrogen gas at high temperature. The products of this reaction are liquid lead and water vapor. As the reaction proceeds, water vapor and excess hydrogen gas leave the glass tube. The diagram and balanced equation below represent this reaction.
Explain why the reaction that occurs in this glass tube can not reach equilibrium.*
Base your answers to questions 14 on the information below and on your knowledge of chemistry.
The equation below represents an equilibrium system of SO2(g), O2(g), and SO3(g). The reaction can be catalyzed by vanadium or platinum.
2SO2(g) + O2(g) ⇌ 2SO3(g) + energy
State how the equilibrium shifts when SO3(g) is removed from the system.*
Base your answers to questions 15 on the information below and on your knowledge of chemistry.
Stamping an identification number into the steel frame of a bicycle compresses the crystal structure of the metal. If the number is filed off, there are scientific ways to reveal the number.
One method is to apply aqueous copper(II) chloride to the number area. The Cu2+ ions react with some iron atoms in the steel frame, producing copper atoms that show the pattern of the number. The ionic equation below represents this reaction.
Fe(s) + Cu2+(aq) → Fe2+(aq) + Cu(s)
Another method is to apply hydrochloric acid to the number area. The acid reacts with the iron, producing bubbles of hydrogen gas. The bubbles form faster where the metal was compressed, so the number becomes visible. The equation below represents this reaction.
2HCl(aq) + Fe(s) → FeCl2(aq) + H2(g)
Describe one change in the HCl(aq) that will increase the rate at which hydrogen bubbles are produced when the acid is applied to the steel frame.*
