AP Chemistry Unit 4 Test Review

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(s)+3Sn2+(aq)→2Al3+(aq)+3Sn(s)

N2 + 3H2 --> 2 NH3 3 moles of N2 and 5 moles of H2 will produce how many moles of NH3?

3.2 mol

ClO2- --> ClO2 + Cl- in acidic solution

5 ClO2- + 4 H+ --> 4 ClO2 + Cl- + 2 H2O

When 44.0 grams of propane (C3H8) undergoes complete combustion, how many grams of water will be produced?

72.0 g

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 Conjugate base C6H5COO−

2 As (s) + 3 Cl2 (g) --> 2 AsCl3

As: oxidized, Cl2: reduced

Another student is asked to formulate a hypothesis about what would happen to sodium metal when it is placed in water. Which of the following hypotheses indicates that the student thinks a chemical change will occur?

B. If sodium is added to water, heat and light will be released.

NaBr + Cl2 --> NaCl + Br2

Balanced: 2 NaBr + Cl2 --> 2 NaCl + Br2

CO + I2O5 --> CO2 + I2 in basic solution

Balanced: 5 CO + I2O5 --> 5 CO2 + I2

Fe2O3 + CO --> Fe + CO2 in acidic solution

Balanced: Fe2O3 + 3 CO --> 2 Fe + 3 CO2

Balanced equation for Ca(OH)2(s) dissolution in pure water?

Ca(OH)2 → Ca2+ + 2OH-

Cr+ + Sn4+ --> Cr3+ + Sn2+

Cr+: oxidized, Sn4+: reduced

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+(aq)→Fe3+(aq)+e−

Strong acids that always dissociate?

HCl, HBr, HI, H2SO4, HNO3, HClO4, HClO3

3 Hg2+ + 2 Fe (s) --> 3 Hg2 + 2 Fe3+

Hg2+: reduced, Fe: oxidized

2 Mg + O2(g) --> 2 MgO What is the limiting reactant if 4 mol of Mg is reacted with 4 mol of oxygen?

Mg

Sr(NO3)2 is soluble in water. Write a balanced equation illustrating the dissolution (dissolving in water) of Sr(NO3)2(s).

Sr(NO3)2 -> Sr 2+ 2(NO3) 1-

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.

Chemical changes

reactivity with acid or flammability are examples of a reaction, Heat or light being produced is evidence of a chemical change, Formation of a precipitate (ppt)

According to the balanced equation above, how many moles of sulfurous acid are needed to react completely with 100 mL of 0.20 M potassium permanganate solution?

0.050 moles

According to the balanced reaction above, how many moles of reactant is left over when 3.6 grams of hydrochloric acid (36 g/mol) and 2.4 grams of magnesium reacts?

0.050 moles

Apply the solubility rules to the following compounds and determine if they soluble or insoluble. 1. Na2SO4 2. BaCO3 3. NaI

1. soluble 2. insoluble 3. soluble

When 72 grams of hydrochloric acid and 24 grams of magnesium react, how many moles of magnesium chloride will be produced?

1.0 moles

Cr(OH)3 + Br2 --> CrO42- + Br- in basic solution

10 OH- + 2 Cr(OH)3 + 3 Br2 --> 2 CrO42- + 8 H2O + 6 Br-

When 54.0 g of aluminum metal (27.0 g/mol) reacts according to the equation above, what is the maximum mass of aluminum oxide that can be produced?

102 g

When 16.0 g of oxygen (32.0 g/mol) reacts according to the equation above, what is the maximum mass of carbon dioxide that can be produced?

13.2 g

O2 + Sb --> H2O2 + SbO2- in basic solution

2 OH- + 2 Sb + 3 O2 + 2 H2O --> 2 SbO2- + 3 H2O2

According to the balanced equation above, how many moles of oxygen are needed to react completely with 22.0 grams of propane?

2.50 moles

Titration reveals that 11.6 mL of 3.0 M sulfuric acid are required to neutralize the sodium hydroxide in 25.00 mL of NaOH solution. What is the molarity of the NaOH solution? H2SO4(aq) + 2NaOH(aq) → 2H2O(l) + Na2SO4(aq)

2.8 M

When 2.00 moles of each hydrochloric acid and magnesium react, how many liters of hydrogen gas will be produced (at STP)?

22.4 L

When 41.0 g of sulfurous acid (82.0 g/mol) reacts according to the equation above, what is the maximum mass of manganese II sulfate (151 g/mol) that can be produced?

30.2 g

According to the balanced equation above, how many moles of aluminum are needed to react completely with 96.0 grams of oxygen?

4.00 moles

When 27.0 grams of aluminum reacts with excess oxygen gas, how many grams of aluminum oxide (102 g/mol) will be produced?

51.0 g

HCOOH + MnO4- --> CO2 + Mn2+ in acidic solution

6 H+ + 2 MnO4- + 5 HCOOH --> 2 Mn2+ + 8 H2O + 5 CO2

When 158 grams of potassium permanganate (158 g/mol) reacts completely with sulfurous acid, how many grams of potassium sulfate (135 g/mol) will be produced?

67.5 g

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.

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+(aq)+Cl−(aq)→AgCl(s)

A student is carrying out various experiments in a laboratory. In one experiment, the student mixes two clear, colorless solutions together, and a yellow precipitate is formed. The student determines that this is evidence of a chemical reaction. Do you agree with the student? Justify your answer.

Agree with the student. This is an example of a chemical reaction because a precipitate is formed. When a new substance is formed from two substances that have different chemical properties that the original solutions.

Define a spectator ion.

An ion that isn't a part of the reaction, alone, and on both sides of the equation

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.

Diagram with four water molecules for Ca(OH)2(s)?

Ca2+ in the center with the oxygen pointing towards the center and the two hydrogens pointing away

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+(aq)+2e−→Cu(s)

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(aq)+OH−(aq)→H2O(l)+F−(aq)

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.

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(aq)+H+(aq)→NH4+(aq)

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.

Fe3O4

Oxidation #: Fe: +8/3, O: -2

H2CO3

Oxidation #: H: +1, O: -2, C: +4

LiH

Oxidation #: Li: +1, H: -1

NO2-

Oxidation #: N: +3, O: -2

N2

Oxidation #: N: 0

Zn(OH)42-

Oxidation #: Zn: 2+, H: +1, O: -2

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 the following changes would double the volume of SO2 produced at the same temperature and pressure? (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 these are the required stoichiometric amounts

A student is given a small mass of baking soda and a sample of vinegar. The student is asked to predict what will happen when the two substances are added together, as well as whether a physical or a chemical process will occur. What prediction should the student make, and how could she provide evidence to justify her answer?

When baking soda and vinegar react together, a gas forming reaction occurs. The formation of carbon dioxide will result in new bonds being made and an exothermic reaction. It takes energy to break apart the baking soda and vinegar and energy is released when carbon dioxide, water and sodium acetate are formed. The production of heat from the reaction as well as the observation of gas evolution are evidence of a chemical change.

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

a Brønsted-Lowry base

HF(aq) + NH3(aq) --> F-(aq) + NH4(aq)

acid base reaction

Ca3(PO4)2(s) + H3PO4(l) --> Ca(H2PO4)2

coefficient for H3PO4(l) is 4

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 20.0mL of NaOH(aq) had been added to the flask. How does the amount of HC2H3O2(aq) in the flask after the addition of 5.0mL of NaOH(aq) compare to the amount of HC2H3O2(aq) in the flask after the addition of 1.0mL of NaOH(aq), and what is the reason for this result?

it is less because more HC2H3O2(aq) reacted with the 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

Physical properties

shape, solubility, phase, separation of mixtures are examples of changes that do not change the chemical composition of a substance