Two Students Measured an Equilibrium Constant for the Same Chemical

question 88

Multiple Choice

Two students measured an equilibrium constant for the same chemical reaction. Ken obtained a value of 130 for the equilibrium constant, but Barbie obtained a value of 11.4. The instructor checked their results and said they were both correct. How can that be?

• A)The values vary according to the way the measurement is made.Ken must have measured product concentrations, while Barbie measured reactant concentrations.
• B)The values vary according to the starting conditions of the reaction prior to equilibrium.Ken must have started with all reactants, while Barbie must have started with all products.
• C)The values vary according to the stoichiometric coefficients that are used.The balancing coefficients that Ken used must have been twice those that Barbie used.
• D)The values vary according to direction of the reaction.Ken must have used the reverse reaction.
• E)The instructor must have made a mistake, because the equilibrium constant for a reaction must always be the same.

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Definitions:

Clamp-on Ammeter

A measuring instrument that can measure the current flow in a conductor without requiring any physical contact or disconnecting the circuit.

Ayrton

Refers to Hertha Ayrton, a British engineer, mathematician, physicist, and inventor, known for her work on electric arcs and ripples in sand and water.

D'Arsonval

Refers to a type of galvanometer used for detecting and measuring small electric currents by the mechanical movement it produces through a magnetic field.

D'Arsonval Meter

A type of ammeter, based on the D'Arsonval galvanometer, used to measure electric current with a moving coil in a magnetic field.