AP Chemistry Unit 4-6 Review

5.3 After a certain pesticide compound is applied to crops, its decomposition is a first-order reaction with a half-life of 56 days. What's the rate constant, k, for the decomposition reaction?

0.012 day-1

4.1 A chemistry teacher conducted several demonstrations, and students recorded their observations. For one of the demonstrations, a student concluded that a physical change occurred, but not a chemical change. What observation could the student have made of the results of the demonstration?

1 piece of solid substance was changed into small pieces

6.5 How much energy is required to melt 64 g of methane (mm = 16 g/mol) at 90 K?

3.8 kJ

6.4 A hot iron ball is dropped into a 200. g sample of water initially at 50°C. If 8.4 kJ of heat is transferred from the ball to the water, what is the final temperature of the water? (The specific heat of water is 4.2 J/(g·°C).)

60 degrees C

4.7 What best describes the process that occurs as NH3 is added to water?

Acid-base reaction, a proton is exchanged from H2O to NH3

5.1 Which of the following will most likely increase the rate of the reaction C2H4 (g) + H2 (g) --> C2H6 (g)

Adding a heterogeneous catalyst to the reaction system

4.2 A student combines a solution of NaCl (aq) with a solution of AgNO3 (aq), and a precipitate forms. What's the balanced net ionic equation for the formation of the precipitate?

Ag+ (aq) + Cl- (aq) --> AgCl (s)

6.1 For a classroom demonstration, a chemistry teacher puts samples of 2 different pure solid powders in a beaker. They place the beaker on a small wooden board with a wet surface, then stirs the contents of the beaker. After a short time, students observe that the bottom of the beaker is frozen to the wood surface. The teacher asks the students to make a claim about the observation and to justify their claims. What's the best claim and justification based on the students' observation?

An endothermic chemical change occurred because the temperature of the beaker and the water on the board decreased as heat was absorbed by the reaction

5.5 What best helps explain why an increase in temperature increases the rate of a chemical reaction?

At higher temperatures, high-energy collisions happen more frequently

4.1 A student combined 2 colorless aqueous solutions. One of the solutions contained Na2CO3 as the solute, and the other contained HCl. What experimental result would be evidence that a chemical reaction occurred when the solutions were combined?

Bubbles formed as the 2 solutions were combined

4.4 A beaker was half filled with freshly distilled H2O and placed on a hot plate. As the temperature of the water reached 100°C, vigorous bubbling was observed in the beaker. The gaseous contents of the bubbles were analyzed. The presence of what substance would support the claim that the observed phenomenon was a physical change?

H2O (g)

4.2 What's the correct net ionic equation of the neutralization reaction between hydrofluoric acid and sodium hydroxide in aqueous solution?

HF (aq) + OH- (aq) --> H2O (l) + F- (aq)

4.8 Based on the Bronsted-Lowry theory of acids and bases, what species can act as both a conjugate acid and a conjugate base?

HS-

4.2 What's the correct net ionic equation of the reaction that occurs when aqueous solutions of ammonia and hydrochloric acid are combined?

NH3 (aq) + H+ (aq) --> NH4+ (aq)

4.4 A student combines a solution of NaCl (aq) with a solution of AgNO3 (aq), and a precipitate forms. What's evidence that ionic bonds formed during the precipitation?

Precipitate has a high melting point

4.1 A student was given 2 clear liquids; colorless and dark-blue. They were asked to combine the liquids in a beaker and record observations. What result, if true, would provide the best evidence that a chemical change occurred as the liquids were combined?

Resulting mixture was cloudy

4.8 In the reaction between C5H5N (aq) and HCl (aq), C5H5N acts as:

a Bronsted-Lowry base

6.3 A 30. g sample of Al (s) is heated to 50 degrees C and placed in a calorimeter containing 150g of water at 20 degrees C. As the system approaches thermal equilibrium, energy is transferred

from the Al (s) to the water and the temperature of the Al (s) decreases

5.11 The role of a catalyst in a chemical reaction is to

lower the activation energy for the reaction

4.5 A student combines a solution of NaCl (aq) with a solution of AgNO3 (aq), and a precipitate forms. Assume that 50.0 mL of 1.0 M NaCl (aq) and 50.0 mL of 1.0 AgNO3 (aq) were combined. If 50.0 mL of 2.0 M NaCl (aq) and 50.0 mL of 1.0 M AgNO3 (aq) were combined, the precipitate formed would

not change, because the amount of AgNO3 (aq) didn't change