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AP Chemistry > Chapter 4 Review > Flashcards

Chapter 4 Review Flashcards

1
Q

20.0 mL of acetone are mixed with 2.0 mL of ethanol. Both chemicals are liquids and miscible with each other. Which is the solvent in this solution?

A

acetone

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2
Q

What is the easiest way to determine that a suspension rather than a solution is formed when a liquid and a solid are mixed?

A

the mixture scatters light

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3
Q

An aqueous solution of sodium chloride is placed in an electric circuit. A light bulb connected to the circuit is weakly illuminated, showing that a weak current is passing through it. How can the conductivity of the solution be increased?

A

by adding calcium chloride (CaCl2 ) to the solution

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4
Q

You have 250 mL of a 0.80 M solution of silver nitrate AgNO3 (169.87 g / mol) dissolved in water. How many grams of AgNO3 does the solution contain?

A

34 g

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5
Q

If 30. g of potassium iodide KI (166.00 g / mol) is dissolved in 250 g of water, what is the molality of this solution?

A

0.72 molal

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6
Q

You have 50. mL of a 1.7 M solution of acetic acid dissolved in water. Approximately how many milliliters of water must be added to dilute it to a 0.20 M solution? (assume volumes are additive)

A

380 mL

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7
Q

Suppose 50.0 g of alcohol are dissolved in 230. g of water. What is the percent of alcohol by mass of the solution?

A

17.9%

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8
Q

Solid iodine (I2 ) is nearly insoluble in water, somewhat soluble in ethanol, and very soluble in hexane. Based on this information, what can you conclude about I2?

A

It contains a nonpolar bond.

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9
Q

Which of these diagrams best represents a solution of cyclohexane (the solute) dissolved in hexane (the solvent)? (Cyclohexane is a nonpolar compound composed of hydrogen and carbon.)

A

Cyclohexane and hexane are both nonpolar compounds. Therefore, the solution of these compounds will depend on entropy rather than on dipole interactions between the solvent and the solute. Entropy acts to increase the randomness of a system. Therefore, the molecules of cyclohexane and hexane will be dispersed randomly throughout the solution. Of the four diagrams, choice A shows the most disordered arrangement of these two molecules.

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10
Q

The compound CH3(CH2 )4CH2OH is only slightly soluble in water. (This compound is identical to hexane except that one of the hydrogen atoms has been replaced with the −OH group of an alcohol.) A second compound has the formula HOCH2(CH2 )4CH2OH. (It is identical to the first compound except that it has two −OH groups instead of one.) How is the solubility of the second compound likely to compare to that of the first compound in water?

A

The second compound is likely to be more soluble in water.

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11
Q

Which of these methods would best allow you to distinguish between a sample of pure water and a sample of pure ethanol?

A

Stir several grams of Potassium Chloride into each sample.

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12
Q

The fluid inside and surrounding the cells of your body is an aqueous solution. The membrane around cells that forms the boundary between these two solutions consists mainly of compounds called phospholipids. These compounds have two parts: One part is polar and one part is nonpolar. Which of these diagrams represents the structure of a cell membrane?

A

In this structure, the polar ends of the phospholipids are exposed only to the aqueous solutions inside and outside the cell. Because polar compounds will dissolve in aqueous solutions, this arrangement will tend to increase the stability of the membrane. In addition, the nonpolar ends of the phospholipids are exposed only to the nonpolar ends of other phospholipids. Because nonpolar compounds tend to dissolve in other nonpolar compounds, this arrangement will also increase the stability of the membrane. Of the four choices given, answer C will be the most stable.

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13
Q

A solution of barium nitrate (Ba(NO3 )2 ) is combined with a solution of copper(II) sulfate (CuSO4 ). What is the overall precipitation reaction that will occur?

A

Ba2+ + 2NO3− + Cu2+ + SO42− → BaSO4 (s) + 2NO3− + Cu2+

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14
Q

A solution of silver nitrate (AgNO3 ) is added to a solution of sodium hydroxide (NaOH). In the precipitation reaction that occurs, which ions will be spectator ions?

A

Na+ and NO3−

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15
Q

Suppose you have a solution of K2SO4. If you want to separate the potassium and sulfate ions from each other, which of these should you add?

A

a solution of Pb(NO3 )2

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16
Q

The nitarate of an unknown cation is mixed with four different solutions. the results of these mixtures are shown below Solution Result NaCl no precipitate Na2SO4 precipitate NaOH no precipitate Na2CO3 precipitate Based on these results which of these is most likely the unknown cation

A

Ba2+

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17
Q

What is the total ionic equation for a reaction between a solution of sodium hydroxide (NaOH) and a solution of perchloric acid (HClO4 )?

A

Na+ + OH − + ClO4− + H + → Na+ + ClO4− + H2O

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18
Q

a solution of an acid is mixed with a solution of a base. the neutral mixture that results contains magnesium nitrate (Mg(NO3)2). this mixture could have resulted from the combination of which of these pairs of solutions

A

a solution of Mg(OH)2 and a solution of HNO3

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19
Q

Which of these aqueous solutions is likely to be the best electrical conductor?

A

a 0.10 M solution of hydrochloric acid, HCl

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20
Q

What is the total number of electrons transferred in the following oxidation-reduction reaction?
2Al(s) + 3Cu2+ (aq) + 6Cl − (aq) →
2Al 3+ (aq) + 6Cl − (aq) + 3Cu (s)

A

6

21
Q

What type of reaction is shown below?

Cu2+ (aq) + SO42− (aq) + 2Na+ (aq) + S2− (aq) → 2Na+ (aq) + SO42− (aq) + CuS (s)

A

precipitation

22
Q

What is the oxidation half-reaction of the following redox reaction?

2Fe(s) + 6H + (aq) + 6Cl − (aq) → 2Fe3+ (aq) + 6Cl − (aq) + 3H2(g)

A

2Fe (s) → 2Fe3+ (aq) + 6e−

23
Q

Which of these titrations will require the greatest volume of base to reach the last equivalence point?

A

50 mL of 0.01 M, phosphoric acid, H3PO4 titrated with 0.01 M KOH

24
Q

A 0.0680 M solution of KOH is used to titrate 42.3 mL of H3PO4, a triprotic acid. The initial reading of the buret is 61.7 mL, and the final reading is 12.4 mL. What is the molar concentration of the H3PO4 solution?

A

0.0265 M

25
Q

Why couldn’t a 0.22 M solution of ammonia (NH3 ) be titrated with a 0.22 M solution of sodium hydroxide (NaOH)?

A

Sodium hydroxide is incapable of neutralizing ammonia, since both are bases.

26
Q

It takes 34.3 mL of a 0.398 M solution of HClO3 to titrate 40.0 mL of a solution of Mg(OH)2. How many grams of magnesium does the titrated solution contain?

A

0.166 g

27
Q

It takes 34.8 mL of a 0.0482 M solution of KMnO4 to titrate 20.4 mL of a solution of Na2C2O4 (sodium oxalate) in the presence of excess acid. What is the concentration of the Na2C2O4 solution? (The net ionic equation of the redox reaction is shown below.)

2 MnO4− + 5 C2O42− + 16 H + → 2 Mn2+ + 10 CO2 + 8 H2O

A

0.205 M

28
Q

Suppose that you titrate 18.8 mL of a solution of sodium sulfite (Na2SO3 ) with a 0.0772 M solution of potassium dichromate (K2Cr2O7 ) in the presence of excess acid. The products of the titration reaction include sulfate ions, chromium(III) ions, and water. Which of the following pieces of information would allow you to calculate the concentration of the original sodium sulfite solution?

Cr2O72− + 3SO32− + 8H + → 2Cr3+ + 3SO42− + 4H2O

A

The volume of potassium dichromate used in the titration

29
Q

It takes 26.9 mL of a 0.0854 M solution of K2Cr2O7 to titrate 31.0 mL of a solution of Na2SO3 in the presence of an excess of acid. What is the concentration of Na2SO3 in the original solution? (The net ionic equation of the redox reaction is shown below.)

Cr2O72− + 3SO32− + 8H + → 2Cr3+ + 3SO42− + 4H2O

A

0.222 M

30
Q

Which of these is not a similarity between redox titrations and acid-base titrations?

A

Both involve changes in the oxidation state of atoms.

31
Q

A sample of a barium halide has a mass of 2.34 g. When the sample is treated with an excess of sulfuric acid, 1.84 g of barium sulfate (BaSO4 ) precipitate. What is the identity of the halide in the original barium compound?

A

bromine

32
Q

Suppose you want to use gravimetric analysis to determine the concentration of iron(III) ions in a solution. Which of these steps would not eliminate a source of error in the analysis?

A

measuring the solution’s volume after the precipitation reaction, rather than before

33
Q

A 2.16 g sample of a silver alloy is dissolved in nitric acid. (An alloy is a solid solution of metals.) When an excess of sodium chloride is added to the solution, 1.42 g of AgCl precipitate. What is the percent by mass of silver in the alloy? (Assume that all the silver in the sample precipitates as AgCl.)

A

49.5%

34
Q

Which statement about oxidation states (or numbers) is not correct?

A

Because the electronegativity difference can be small, electronegativity is not an important consideration when determining oxidation states.

35
Q

What are the oxidation numbers for magnesium and oxygen (in that order) in the MgO molecule?

A

+2, −2

36
Q

What is an oxidation state?

A

It is a charge assigned to an atom. It tells you how many electrons the atom controls in a compound.

37
Q

Let’s look at the methane molecule, CH4.

We learned that the electronegativity difference between carbon and hydrogen is very slight. Which statement about this molecule is not correct?

A

There are four (very) polar C–H bonds in the molecule. They are polar towards the carbon atom because carbon is more electronegative.

38
Q

Look at the reaction between oxalate and iodate ions.
5C2O42-(aq) + 2IO3-(aq) + 12H+(aq) ->
10CO2(g) + I2(aq) + 6H2O(l)
Which of the following correctly identifies the oxidizing agent, the reducing agent, the oxidized compound, and the reduced compound

A

IO3− is the oxidizing agent and the reduced compound.

C2O42− is the reducing agent and the oxidized compound.

39
Q

Which of the following best describes what a redox reaction is?

A

It is a reaction in which the oxidation state of one element increases and the oxidation state of another element decreases.

40
Q

Which of the following is not a correct rule for determining oxidation states?

A

Any compound’s component species have oxidation states that add up to zero.

41
Q

Which of the following correctly identifies the oxidizing agent and the reducing agent?

3H2S(aq) + 2NO3−(aq) + 2H +(aq) → 3S(s) + 2NO(g) + 4H2O(l)

A

H2S is the reducing agent. NO3− is the oxidizing agent.

42
Q

Which of the following correctly summarizes the electron transfer in the given reaction?

10H +(aq) + 8I −(aq) + SO42−(aq) → H2S(aq) + 4I2(aq) + 4H2O(l)

A

I − → I 0; S6+ → S2−

43
Q

Which of the following correctly describes the two half-reactions in the redox reaction below?

CuS(s) + NO3− (aq) → Cu2+ (aq) + SO42− (aq) + NO(g)

A

CuS(s)→ Cu2+ (aq) + SO42− + 8e − is the oxidation step.

NO3− (aq) + 3e −→ NO(g) is the reduction step.

44
Q

Suppose that you have to balance the following reaction in basic solution.

NH3(aq) + ClO− (aq) → N2H4(aq) + Cl − (aq)

Which of the following is not a step you would take to balance this reaction?

A

After balancing the oxygen atoms, multiply one of the half-reactions by 2 to balance electrons

45
Q

How does the half-reaction (or half-cell) balancing method differ from the oxidation number method?

A

The half-reaction (or half-cell) method isolates the two half-reactions (i.e., the oxidation step and the reduction step) that, together, comprise a redox reaction.

46
Q

This list of reduction reactions is a helpful tool for predicting how two metals and metal ions will interact with one another. Which statement about the redox activity series is not correct?

A

As you move down the list, the ability of the metal component to reduce another metal increases.

47
Q

This list of reduction reactions is a helpful tool for predicting how two metals will interact with one another. Suppose that we are looking for a metal to react in a specific manner with magnesium. Which of the following correctly describes and lists the metal that will achieve our desired goal?

A

We want a metal that will cause magnesium ion(Mg2+ ) to be reduced spontaneously. We choose calcium metal.

48
Q

Which of the following correctly shows what happens in the two half-reaction steps (oxidation and reduction) in a redox reaction?

A 
Oxidation
loss of electrons 
increase in the oxidation number
-2 -1 0 +1 +2
Reduction
gain of electrons
decrease in the oxidation number

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