Textbook Ch.4: Reactions in Aqueous Solution

Question 1

Molarity

Answer 1

the concentration of a solute in solution

molarity (M) = moles of solute / liters of solution

Question 2

What does the symbol [ ] represent?

Answer 2

the molarity of a species in solution

Question 3

What can the molarity of a solution be used to calculate?

Answer 3

• The number of moles of solute in a given volume of solution
• The volume of solution containing a given number of moles of solute

Question 4

Precipitate

Answer 4

formed when two different ionic compounds are mixed, an insoluble solid separates out of a solution

• The precipitate that forms is itself ionic
• The cation comes from one solution, the anion comes from the other

Question 5

Net ionic equation

Answer 5

the chemical equation that shows only those elements, compounds, and ions that are directly involved in the chemical reaction.

Question 6

What does a net ionic equation have to show?

Answer 6

• Atom balance (same number of atoms of each element on both sides)
• Charge balance (must be the same total charge on both sides)

Question 7

Acid

Answer 7

a species that produces H⁺ ions in water solution

Question 8

Base

Answer 8

a species that produces OH⁻ ions in a water solution

Question 9

Strong acids

Answer 9

acids that ionize completely, forming H⁺ ions and anions

Question 10

Weak acids

Answer 10

acids that only partially ionize to H⁺ ions in water

Question 11

What does a double arrow ⇌ symbol mean?

Answer 11

the reaction does not go into completion, instead a mixture is formed containing significant amounts of both products and
reactants

Question 12

Strong bases

Answer 12

bases that completely ionize into OH⁻ ions and cations

Question 13

Weak bases

Answer 13

produce OH⁻ ions by reacting with water molecules, acquiring H⁺ ions and leaving OH⁻ ions behind

Question 14

Strong acid-strong base reactions

Answer 14

acids and bases both completely and the H⁺ and OH⁻ ions react with each other to form H₂O molecules, this reaction is referred to as neutralization

Question 15

What is the net ionic equation for a strong acid-strong base reaction?

Answer 15

H⁺(aq) + OH⁻(aq) —> H₂O

Question 16

Weak acid-strong base reactions

Answer 16

a two-step reaction occurs

1. Ionization of the weak acid into H+ and an anion
2. Neutralization of the H+ ions produced from (1) react with the OH- of the base to produce water

Question 17

What is the net ionic equation for a weak acid-strong base reaction?

Answer 17

HB(aq) + OH⁻(aq) —> H₂O + B⁻(aq)

Question 18

Strong acid-weak base reactions

Answer 18

two-step reaction occurs

1. Acid reacts with water to form cations and OH⁻
2. Neutralization occurs when ions produced from (1) react with the OH⁻ of the base to produce water

Question 19

What is the net ionic reaction for a strong-acid weak base reaction?

Answer 19

H⁺(aq) + B(aq) —> BH⁺(aq)

Question 20

Titration

Answer 20

when acid-base reactions in water solution are commonly used to determine the concentration of a dissolved species or its
percentage in a solid measure, so the volume of a standard solution (a solution of known concentration) required to react with a measured amount of sample is measured

Question 21

Redox reaction

Answer 21

a reaction in an aqueous solution that involves a transfer of electrons between two species

Question 22

Which species in a redox reaction is considered to be oxidized?

Answer 22

the species that loses (i.e. donates) electrons

Question 23

Which species in a redox reaction is considered to be reduced?

Answer 23

the species that gains (i.e. received) electrons

Question 24

How are redox reactions split?

Answer 24

it can be split into two half-equations, one of oxidation and the other of reduction

Question 25

What is unique to redox reactions?

Answer 25

- Oxidation and reduction occur together in the same reaction; you can't have one without the other - there is no net charge in the number of electrons in a redox reaction. Those given off in the oxidation half-reaction are taken on by another species in the reduction half-reaction

Question 26

Oxidizing agent

Answer 26

the ion or molecule that accepts electrons

Question 27

Reducing agent

Answer 27

the ion or molecule that donates electrons

Question 28

Oxidation number

Answer 28

a concept that is used to simplify the electron bookkeeping in redox reactions

Question 29

The oxidation number of an element in an elementary substance is: (I.e. Cl₂, P₄)

Answer 29

0

Question 30

The oxidation number of an element in a monatomic ion is:

Answer 30

equal to the charge of the ion Ex: in NaCl, sodium has an oxidation number of +1 (because it has a charge of +1) and chlorine has an oxidation number of -1 (because it has a charge of -1)

Question 31

Group 1 elements always have an oxidation number of ____ in their compounds

Answer 31

they always have an oxidation number of +1 because they always exist as +1 ions in their compounds

Question 32

Group 2 elements always have an oxidation number of ____ in their compounds

Answer 32

they always have an oxidation number of +2 because they always exist as +2 ions in their compounds

Question 33

Oxygen is ordinarily assigned an oxidation number of ____ in its compounds

Answer 33

-2 (except for peroxide, where the oxidation number of oxygen is -1)

Question 34

The sum of the oxidation numbers in a neutral species is:

Answer 34

0

Question 35

The sum of oxidation numbers in a polyatomic ion is:

Answer 35

equal to the charge of that ion

Question 36

Define oxidation in terms of increasing/decreasing oxidation number

Answer 36

oxidation is defined as an increase in oxidation number

Question 37

Define reduction in terms of increasing/decreasing oxidation number

Answer 37

reduction is defined as a decrease in oxidation number

Question 38

Half-equation

Answer 38

two equations that come from a redox reaction: one for oxidation (electron loss) and one for reduction (electron gain

Question 39

When balancing half-reactions, what aspects need to be balanced and in what order should you balance them?

Answer 39

1. Number of atoms of the element being oxidized or reduced 2. Oxidation number 3. Charge 4. Hydrogen 5. Oxygen

Question 40

When you are balancing the oxidation number in reduction half-equations, which side do you add electrons onto?

Answer 40

left

Question 41

When you are balancing the oxidation number in oxidation half-equations, which side do you add electrons onto?

Answer 41

right

Question 42

When balancing the charge of a half-equation in an acidic solution, what do you add?

Answer 42

H⁺ ions

Question 43

When balancing the charge of a half-equation in a basic solution, what do you add?

Answer 43

OH⁻ ions

Question 44

In order to put the two half-equations together to balance the entire redox reaction, what should you make sure cancels?

Answer 44

the electrons