AP Chemistry Unit 9

Two identical spoons were electroplated with Ag or Cd through the use of the electrolytic cells illustrated above. A current of 5.00A was supplied to each cell for 600. seconds, and the masses of the spoons before and after the electroplating were recorded. Which of the following mathematical equations can best be used to account for the much larger increase in mass of the spoon electroplated with Ag compared with the spoon electroplated with Cd?

• ΔG°=ΔH°−TΔS°

• ΔG°=−RTlnK

• E=E°−(RT/nF)lnQ

• I=q/t

Graphite, an allotrope of carbon, is converted into cubic diamond through a process that may take a billion years or longer. However, these synthetic diamonds have carbon atoms in a hexagonal lattice. Diamonds with a carbon atoms in a cubic lattice are not produced even though they are thermodynamically more stable than hexagonal diamond. Which of the following best justifies why the synthetic process produces hexagonal diamond and not the more thermodynamically stable cubic diamond?

• The amount of energy required to create new bonds between carbon atoms in cubic diamond is much greater than the amount of energy required to create hexagonal diamond.

• The amount of energy required to create new bonds between carbon atoms in cubic diamond is much smaller than the amount of energy required to create hexagonal diamond.

• The activation energy needed to form cubic diamond is much less than the activation energy needed to form hexagonal diamond.

• The activation energy needed to form cubic diamond is much greater than the activation energy needed to form hexagonal diamond.

Tags

NGSS.HS-PS1-3

The chemical equation above represents the formation of SeF₆(g) from its elements and the table provides the approximate values of S° for Se(s) and SeF₆(g). Based on the data, which of the following mathematical expressions can be used to correctly calculate S° for F₂(g)?

• S=[-337+314-42] J(mol*K)

• S= -[-337-314+42] J/(mol*K)

• S= (1/3)[-337+314-42] J/(mol*K)

• S= -(1/3)[-337-314+42] J/(mol*K)

Entropy is always ________ in the Universe

• increasing

• decreasing

• constant

Tags

NGSS.HS-PS3-4

Which has the HIGHEST entropy change?

• 1 --> 2 particles

• gas --> liquid

• solid --> gas

• low to high temperature (same phase)

Which has a negative sign for S?

• water evaporating

• NaCl dissolving in water

• water freezing

• sublimation of CO2

Which has a positive sign for S?

• 2Na (s) + Cl2 (g) --> 2NaCl (s)

• H2O (g) --> H2O (l)

• H+ (aq) + NO3- (aq) --> HNO3 (l)

• CaCl2 (s) --> Ca2+ (aq) + 2Cl- (aq)

Tags

NGSS.HS-PS3-4

reaction is ALWAYS spontaneous

• - H, - S

• + H, + S

• + H, - S

• - H, + S

Tags

NGSS.HS-PS1-4

a reaction that is exothermic and has a decrease in entropy is

• spontaneous at high temps

• spontaneous at low temps

• always spontaneous

• never spontaneous

Which of the following best describes the role of a catalyst in a chemical reaction?

• A) It increases the activation energy of the reaction.

• B) It decreases the activation energy of the reaction.

• C) It changes the equilibrium position of the reaction.

• D) It is consumed in the reaction.