chapter 4 types of chemical reactions and solutions stoichiometry

Chapter 4

Types of Chemical Types of Chemical Reactions and Solutions Reactions and Solutions

StoichiometryStoichiometry

Copyright © Houghton Mifflin Company. All rights reserved. CRS Question, 4–2

QUESTION

An unknown substance dissolves readily in water but not in benzene (a nonpolar solvent). Molecules of what type are present in the substance? 1) Neither polar nor nonpolar 2) Polar 3) Either polar or nonpolar 4) Nonpolar 5) none of these


ANSWER

2) Polar

Section 4.1 Water, the Common Solvent (p. 127)

The solubility rule for molecular compounds is “like dissolves like”, that is, polar molecules dissolve in polar solvents and nonpolar molecules dissolve in nonpolar solvents.


QUESTION

How many grams of NaCl are contained in 350. mL of a 0.250 M solution of sodium chloride? 1) 41.7 g 2) 5.11 g 3) 14.6 g 4) 87.5 g 5) None of these


ANSWER

2) 5.11 g

Section 4.3 The Composition of Solutions(p. 133)

Volume (L) times concentration (mol/L) gives moles. Moles are then converted to grams.


QUESTION

What volume of 18.0 M sulfuric acid must be used to prepare 15.5 L of 0.195 M H2SO4? 1) 168 mL 2) 0.336 L 3) 92.3 mL 4) 226 mL 5) None of these


ANSWER

M 1 2 V ,

V

1) 168 mL


Use the dilution formula, 1 V = M 2 M is in mol/L and is in L.


QUESTION

The net ionic equation for the reaction of aluminum sulfate and sodium hydroxide contains which of the following species? 1) 3Al

3+(aq)

2) OH–(aq)

3) 3OH–(aq)

4) 2Al3+

(aq) 5) 2Al(OH)3(s)


ANSWER

–

3) 3OH(aq)

Section 4.6 Describing Reactions in Solution(p. 145)

The net ionic equation is found by canceling the spectator ions from the total ionic equation.


QUESTION

Which of the following is a strong acid? 1) HF 2) KOH 3) HClO4 4) HClO 5) HBrO


ANSWER

4

:

3) HClO

Section 4.2 The Nature of Aqueous SolutionsStrong and Weak Electrolytes (p. 129)

Memorization of the list of strong acids will allow one to determine the difference between strong acids and weak acids.


QUESTION

All of the following are weak acids except: 1) HCNO. 2) HBr. 3) HF. 4) HNO2. 5) HCN.


ANSWER

.

2) HBr

Section 4.2 The Nature of Aqueous Solutions: Strong and Weak Electrolytes (p. 129)

Knowing the list of strong acids will allow one to determine which acids are strong and which are weak.


QUESTION

Which of the following is not a strong base? 1) Ca(OH)2 2) KOH 3) NH3 4) LiOH 5) Sr(OH)2


ANSWER

3

3) NH

Section 4.2 The Nature of Aqueous Solutions: Strong and Weak Electrolytes (p. 129)

Knowing the list of strong bases will allow one to determine which bases are strong and which are weak.


QUESTION

The interaction between solute particles and water molecules, which tends to cause a salt to fall apart in water, is called: 1) hydration. 2) polarization. 3) dispersion. 4) coagulation. 5) conductivity.


ANSWER

.

1) hydration

Section 4.1 Water, the Common Solvent (p. 127)

Hydration is the process of water molecules surrounding and stabilizing ions so that they can be pulled into solution.


QUESTION

The concentration of a salt water solution that sits in an open beaker decreases over time.

1) True 2) False


ANSWER

2) False


The amount of water decreases over time so the concentration (mol NaCl/volume of water) increases over time.


QUESTION

The following reactions: Pb

2+ + 2I

– PbI2

2Ce4+ + 2I

– I2 + 2Ce

3+

HOAc + NH3 NH4

+ + OAc

–

are examples of


QUESTION (continued)

1) acid-base reactions. 2) unbalanced reactions. 3) precipitation, acid-base, and redox

reactions, respectively. 4) redox, acid-base, and precipitation

reactions, respectively. 5) precipitation, redox, and acid-base

reactions, respectively.


ANSWER

-

24+ 3+

3

5) precipitation, redox, and acid base reactions, respectively.

Section 4.5 Precipitation Reactions (p. 140)

PbI is insoluble, Ce changes to Ce and HOAc is an acid while NH is a base.


QUESTION

Which of the following salts is insoluble in water? 1) Na2S 2) K3PO4 3) Pb(NO3)2 4) CaCl2 5) All of these are soluble in water.


ANSWER

5) All of these are soluble in water.

Section 4.5 Precipitation Reactions (p. 140)

According to the solubility rules for ionic compounds, compounds containing Group IA ions or nitrate ions will always be soluble. Compounds containing halides are generally soluble, aside from silver, lead and mercury(I) halides.


QUESTION

When NH3(aq) is added to Cu2+

(aq), a precipitate initially forms. Its formula is: 1) Cu(NH3)4

2+

2) Cu(NO3)2 3) Cu(OH)2 4) Cu(NH3)4

2+

5) CuO


ANSWER

2

s

3 4+

3) Cu(OH)

Section 4.4 Types of Chemical Reaction(p. 140)

Ammonia produces hydroxide ion in water:NH + H2O NH + OH

–


QUESTION

In the balanced molecular equation for the neutralization of sodium hydroxide with sulfuric acid, the products are: 1) NaSO4 + H2O 2) NaSO3 + 2H2O 3) 2NaSO4 + H2O 4) Na2S + 2H2O 5) Na2SO4 + 2H2O


ANSWER

5) Na2SO4 + 2H2O Section 4.8 Acid-Base Reactions (p. 149) The salt is made from the anion of the acid and the cation of the base.


QUESTION

What mass of NaOH is required to react exactly with 25.0 mL of 1.2 M H2SO4? 1) 1.2 g 2) 1.8 g 3) 2.4 g 4) 3.5 g 5) None of these


ANSWER

-

2 4

2 4 2

2

3) 2.4 g

Section 4.8 AcidBase Reactions (p. 149)

Remember that the reaction is 2NaOH + H SO Na SO + 2H O, so there are two moles of

NaOH used per one mole of H SO4.


QUESTION

In which of the following does nitrogen have an oxidation state of +4? 1) HNO3 2) NO2 3) N2O 4) NH4Cl 5) NaNO2


ANSWER

2

-

–

2O2

2) NO

Section 4.9 Oxidation Reduction Reactions(p. 154)

Oxygen almost always has an oxidation state of 2 when part of a compound. The exception is

when it is part of a peroxide. For example, hydrogen peroxide H . Then it has an oxidation state of –1.


QUESTION

In the reaction 2Cs(s) + Cl2(g) 2CsCl(s), Cl2 is 1) the reducing agent. 2) the oxidizing agent. 3) oxidized. 4) the electron donor. 5) two of these


ANSWER

-

2) the oxidizing agent.


Metals lose electrons, so they are oxidized, making the other reactant an oxidizing agent.


QUESTION

Which of the following statements is(are) true? Oxidation and reduction: 1) cannot occur independently of each other. 2) accompany all chemical changes. 3) describe the loss and gain of electron(s),

respectively. 4) result in a change in the oxidation states of

the species involved. 5) 1, 3, and 4 are true


ANSWER

.

-

5) 1, 3, and 4 are true


(2) is false because certain reactions, such as double displacement reactions, are not redox reactions.


QUESTION

How many of the following are oxidation-reduction reactions? NaOH + HCl NaCl + H2O Cu + 2AgNO3

2Ag + Cu(NO3)2 Mg(OH)2

MgO + H2O N2 + 3H2

2NH3


QUESTION (continued)

1) 0 2) 1 3) 2 4) 3 5) 4


ANSWER

-

3) 2

Section 4.9 OxidationReduction Reactio ns(p. 154)

If an element is found on the reactant’s side, this is almost always a redox reaction, since an element usually becomes part of a compound during a chemical reaction.