AP Chemistry Exam

X(g) + Y(g) -> 2 Z(g) When 4.00 mol each of X(g) and Y(g) are placed in a 1.00 L vessel and allowed to react at constant temperature according to the equation above, 6.00 mol of Z(g) is produced. What is the value of the equilibrium constant, Kc ?

• 3

• 6

• 8

• 16

• 36

Tags

NGSS.HS-PS1-6

NaOH(aq) + HCl(aq) → H₂O(l) + NaCl(aq) A student is trying to determine the heat of reaction for the acid-base neutralization reaction represented above. The student uses 0.50 M NaOH and 0.50 M HCl solutions. Which of the following situations, by itself, would most likely result in the LEAST error in the calculated value of the heat of reaction

• The thermometer was incorrectly calibrated and read 0.5 Celsius degree too high during the procedure.

• The volume of the acid solution added to the calorimeter was actually 1.0 mL less than what was recorded.

• The calorimeter was poorly insulated, and some heat escaped to the atmosphere during the procedure.

• The actual molarity of the base solution was 0.53 M but was recorded as 0.50 M.

• The final temperature of the mixture was taken before the contents of the calorimeter had reached thermal equilibrium.

Tags

NGSS.HS-PS3-2

NGSS.HS-PS3-4

A molecular solid coexists with its liquid phase at its melting point. The solid-liquid mixture is heated, but the temperature does not change while the solid is melting. The best explanation for this phenomenon is that the heat absorbed by the mixture

• is lost to the surroundings very quickly

• is used in overcoming the intermolecular attractions in the solid

• is used in breaking the intramolecular bonds within the molecules of the solid

• causes the nonbonding electrons in the molecules to move to lower energy levels

Tags

NGSS.MS-PS1-4

NGSS.MS-PS3-4

NGSS.MS-PS3-5

Which of the following substances is a strong electrolyte when dissolved in water?

• Sucrose

• Ethanol

• Sodium nitrate

• Acetic acid

• Ammonia

Tags

NGSS.HS-PS1-3

Concentrations of colored substances are commonly measured by means of a spectrophotometer. Which of the following would ensure that the correct values are obtained for the measured absorbance?

I. There must be enough sample in the test tube to cover the entire light path

II. The instrument must be calibrated using a component of the standard solution (“blank”)

III. The solutions must be saturated

• I only

• II only

• I and II

• II and III

• I, II and III

Which of the transition arrows in the above energy level diagram best describes the energy change for this reaction?

• A

• C

• B

• E

• F

Tags

NGSS.HS-PS1-4

What happens to an electron as it gets farther from the nucleus of an atom?

• I only

• II only

• I and II

• I and III

• I, II and III

Tags

NGSS.HS-PS1-1

The atomic radius of main-group elements generally increases down a group because __________.

• effective nuclear charge increases down a group

• effective nuclear charge decreases down a group

• effective nuclear charge zigzags down a group

• the principal quantum number of the valence orbitals increases

• both effective nuclear charge increases down a group and the principal quantum number of the valence orbitals increases

Tags

NGSS.HS-PS1-1

NGSS.HS-PS1-2

A reaction has a very large equilibrium constant of 3.3 x 10¹³. Which statement is NOT true about this reaction?

• the reaction is very fast.

• The reaction is essentially complete.

• The reaction is spontaneous.

• The equilibrium constant will change if the temperature is changed.

• The reaction is thermodynamically favorable.

The diagram above represents H_2(g) and N_2(g) in a closed container. Which of the following diagrams would represent the results if the reaction shown below were to proceed as far as possible?

N_2(g) + 3H_2(g) ↔ 2NH_3(g)

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Tags

NGSS.MS-PS1-2

NGSS.MS-PS1-5