ap chem unit 4 test

Al(s)→Al3+(aq)+3e− Sn2+(aq)+2e−→Sn(s) Based on the half-reactions represented above, which of the following is the balanced ionic equation for the oxidation-reduction reaction between Al(s) and Sn2+(aq) ?

2Al + 3Sn2+ -> 2Al3+ + 3Sn

When students added 2.0g of NaI crystals to 100.mL of Pb(NO3)2(aq), a yellow precipitate formed. After the solution was filtered, the yellow solid was dried and weighed. Data from the experiment are shown in the table above. Which of the following claims is best supported by the observations?

A chemical change occurred when a yellow, insoluble compound with a larger mass than the original NaI formed.

C6H5COOH(aq)+NaOH(aq)→C6H5COONa(aq)+H2O(l) Which of the following identifies a conjugate acid-base pair in the reaction represented above?

Acid- C6H5COOH Base- C6H5COO-

A student combines a solution of NaCl(aq) with a solution of AgNO3(aq), and a precipitate forms. Which of the following is the balanced net ionic equation for the formation of the precipitate?

Ag+ + Cl- -> AgCl

Na2CO3(aq)+2HCl(aq)→2NaCl(aq)+H2O(l)+CO2(g) A student combined two colorless aqueous solutions. One of the solutions contained Na2CO3 as the solute, and the other contained HCl. The chemical reaction that took place is represented by the equation above. What experimental result would be evidence that a chemical reaction took place when the solutions were combined?

Bubbles formed when the two solutions were combined.

Zn(s)+CuSO4(aq)→Cu(s)+ZnSO4(aq) When a zinc plate is placed in an aqueous solution of copper sulfate, elemental copper forms, as represented by the equation above. Which of the following represents the reduction half-reaction of the reaction?

Cu2+ + 2e- -> Cu

5Fe2+(aq)+MnO4−(aq)+8H+(aq)→5Fe3+(aq)+Mn2+(aq)+4H2O(l) Which of the following represents the oxidation half-reaction based on the balanced ionic equation shown above?

Fe2+ -> Fe3+ + e-

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 which of the following substances would support the claim that the observed phenomenon was a physical change?

H2O(g)

Which of the following is the correct net ionic equation of the neutralization reaction between hydrofluoric acid and sodium hydroxide in aqueous solution?

HF + OH- -> H2O + F-

Based on the Brønsted-Lowry theory of acids and bases, which of the following species can act as both a conjugate acid and a conjugate base?

HS-

Which of the following best describes the process represented above that takes place when NH3 is added to water?

It is an acid-base reaction in which a proton is exchanged from H2O to NH3.

Zn(s)+2HCl(aq)→ZnCl2(aq)+H2(g) When the reaction represented above proceeds, heat is produced. Which of the following best describes the reaction?

It is an oxidation-reduction reaction because zinc is oxidized and hydrogen is reduced.

2Mg(s)+SiCl4(l)→2MgCl2(s)+Si(s) Which of the following statements about the reaction represented above is correct?

It is an oxidation-reduction reaction, and Mg is oxidized.

HC2H3O2(aq)+OH−(aq)→C2H3O2−(aq)+H2O(l) A student carried out a titration using HC2H3O2(aq) and NaOH(aq). The net ionic equation for the neutralization reaction that occurs during the titration is represented above. The NaOH(aq) was added from a buret to the HC2H3O2(aq) in a flask. The equivalence point was reached when a total of 20.0mL20.0mL of NaOH(aq) had been added to the flask. How does the amount of HC2H3O2(aq) in the flask after the addition of 5.0mL5.0mL of NaOH(aq) compare to the amount of HC2H3O2(aq) in the flask after the addition of 1.0mL1.0mL of NaOH(aq), and what is the reason for this result?

It is less because more HC2H3O2(aq) reacted with the base.

Which of the following is the correct net ionic equation of the reaction that occurs when aqueous solutions of ammonia and hydrochloric acid are combined?

NH3 + H+ -> NH4+

A chemistry teacher carried out several demonstrations, and students recorded their observations. For one of the demonstrations, a student concluded that a physical change took place, but not a chemical change. Which of the following observations could the student have made of the results of the demonstration?

One piece of solid substance was changed into small pieces.

A student combines a solution of NaCl(aq) with a solution of AgNO3(aq), and a precipitate forms. Which of the following is evidence that ionic bonds formed during the precipitation?

The precipitate has a high melting point

A student was given two clear liquids; a colorless liquid and a dark-blue liquid. The student was asked to combine the liquids in a beaker and record observations. Which of the following results, if true, would provide the best evidence that a chemical change took place when the liquids were combined?

The resulting mixture was cloudy.

K2SO3(aq)+2HNO3(aq)→2KNO3(aq)+SO2(g)+H2O(l) According to the balanced chemical equation above, when 100.0mL of 0.100MK2SO3(aq) is mixed with 100.0mL of 0.200MHNO3(aq) at 30°C and 1 atm, the volume of SO2 gas produced is 0.24 L. If it is assumed that the reaction goes to completion, which of the following changes would double the volume of SO2 produced at the same temperature and pressure, and why? (For each change, assume that the other solutions and volumes remain the same.)

Using 200.0mL of 0.100MK2SO3(aq) and 200.0mL of 0.200MHNO3(aq), because this provides double the number of moles with the correct stoichiometric ratio

In the reaction between C5H5N(aq) and HCl(aq) represented above, C5H5NC5H5N acts as

a Brønsted-Lowry base

A student combines a solution of NaCl(aq) with a solution of AgNO3(aq), and a precipitate forms. Assume that 50.0mL of 1.0MNaCl(aq) and 50.0mL of 1.0MAgNO3(aq) were combined. According to the balanced equation, if 50.0mL of 2.0MNaCl(aq) and 50.0mL of 1.0MAgNO3(aq) were combined, the amount of precipitate formed would

not change, because the amount of AgNO3(aq) did not change