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Chemistry Chapter 9 > Chapter 9.1 > Flashcards

Chapter 9.1 Flashcards

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1
Q

Intrduction to Redox Reactions?

What is an oxidation reaction?

A

It involves the gain of oxygen or the loss of hydrogen, or loss of electrons

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2
Q

Introduction to Redox Reactions

What is a reduction recation?

A

It involves the gain of hydrogen or the loss of oxygen, or gain of electrons

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3
Q

Introduction to redox Reactions

What is special about redox reactions?

A

Oxidation and reduction
will always occur together

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4
Q

Oxidation Numbers Enable Us to Track Redox Change

How can we determine the movement of electrons happening in a covalent bond?

A

Oxidation states

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5
Q

Oxidation Numbers Enable Us to Track Redox Change

What is an oxidation state?

A

A value we assign to each atom in a compound that is a measure of the electron
control or possession it has relative to the atom in the pure element

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6
Q

Oxidation Numbers Enable Us to Track Redox Change

What do the signs and values of the oxidation states determine?

A

The positive sign shows a loss of electeron control while a negative sign shows a gain of control in electrons. The value shows how many electrons the atom has gained or lost

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7
Q

Strategy for Assigning Oxidation States

What is the oxidation state of free elements (uncombined)?

A

Zero

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8
Q

Strategy for Assigning Oxidation States

What is the oxidation state of simple ions?

A

It is the same as their charge

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9
Q

Strategy for Assigning Oxidation States

What is the oxidation states of atoms in neutral compound?

A

Add up to zero

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10
Q

Strategy for Assigning Oxidation States

What is the oxidation states of all atoms ina polyatomic ion?

A

They must add up to charge on ion

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11
Q

Strategy for Assigning Oxidation States

What is the ususal oxidation state for an element?

A

The charge of its most common ion

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12
Q

Strategy for Assigning Oxidation States

What is the oxidation states of most non-metals and transition elements?

A

Vary in different compounds –
depending on the conditions and other elements present

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13
Q

Strategy for Assigning Oxidation States

What are the usual oxidation numbers for Li, Na, K, H

A

+1

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14
Q

Strategy for Assigning Oxidation States

What are the usual oxidation numbers for Mg, Ca

A

+2

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15
Q

Strategy for Assigning Oxidation States

What are the usal oxidation numbers for F, Cl

A

–1

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16
Q

Strategy for Assigning Oxidation States

What is the usual oxidation state of O?

A

–2

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17
Q

Interpreting Oxidation States

What does a higher poistive number in the oxidation state mean?

A

The more the atom has lost control over electrons, in other words the more
oxidized it is.

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18
Q

Interpreting Oxidation States

What does a higher negative number in the oxidation state mean?

A

The more the atom has gained control over electrons, in other words the more reduced it is

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19
Q

Interpreting Oxidation States

What does an increase and decrease in oxidation state mean?

A

An increase in oxidation stae signifies oxidation and a decrease signifies reduction

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20
Q

Systematic names of compounds use oxidation numbers

How is oxidation number shown in the element?

A

Oxidation number is
shown by inserting
a Roman numeral
in brackets after the
name or symbol of the
element.

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21
Q

Redox Equations

What are half-equations?

A

Equations that represent the seperate oxidation and reduction of elements

22
Q

Redox Equations

What are half-equations?

A

Equations that represent the seperate oxidation and reduction of elements

23
Q

Redox Equations

What are the steps to follow in order to determine the full redox reaction?

A
  1. Assign oxidation states to determine which atoms are being oxidized and which are being reduced.
  2. Write half-equations for oxidation and reduction as follows:
    (a) balance the atoms other than H and O;
    (b) balance each half-equation for O by adding H2O as needed;
    (c) balance each half-equation for H by adding H+ as needed;
    (d) balance each half-equation for charge by adding electrons to the sides with the more positive charge.
    (e) check that each half-equation is balanced for atoms and for charge.
  3. Equalize the number of electrons in the two half-equations by multiplying
    each appropriately
  4. Add the two half-equations together, cancelling out anything that is the same
    on both sides.
24
Q

**Oxidizing and Reducing Agents **

What is the oxidizing agent?

A

The reactant that accepts electrons, it brings about oxidation of the other reactant. In the
process it becomes reduced

25
Q

**Oxidizing and Reducing Agents **

What is the reducing agent?

A

The reactant that supplies the electrons, it brings about reduction and itself becomes oxidized

26
Q

Oxidizing and Reducing Agents

What are examples of oxidizing agents?

A

O2, O3, H+/MnO4–, H+/Cr2O72–, F2, Cl2, conc. HNO3, H2O2

27
Q

**Oxidizing and Reducing Agents **

What are examples of reducing agents?

A

H2, C, CO, SO2, reactive metals

28
Q

**Oxidizing and Reducing Agents **

Whether a species acts as an oxidizing or as a reducing agent actually
depends on what?

A

What is it reacting with as agents can act as either reducing or oxdizing agents based on what they are reacting with

29
Q

Oxiadizing and Reducing Agents

Why is water used as a solvent in redox reactions?

A

Water is weak both as an oxidizing agent and as a reducing agent

30
Q

More reactive metals are stronger reducing agents

What does the strength of oxidizing and reducing agents depend on?

A

Their relative tendencies to lose or gain electrons

31
Q

More reactive metals are stronger reducing agents

Why do metals work as reducing agents?

A

Have a tendency to lose electrons and form positive ions

32
Q

More reactive metals are stronger reducing agents

What makes a metal a strong reducing agent?

A

The ability to lose electrons more readily than others, which means being more recative

33
Q

More reactive metals are stronger reducing agents

How can we check if the metal is more reactive than another?

A

If it is able to reduce ions of other metal

34
Q

More reactive non-metals are stronger oxidizing agents

Why do non-metlas work as oxidizng agents?

A

React by gaining electrons
and forming negative ions, remove electrons from other substances

35
Q

More reactive non-metals are stronger oxidizing agents

What makes a non-metal a strong oxidizing agent?

A

The ability to gain electrons more readily which decreases down a group

36
Q

More reactive non-metals are stronger oxidizing agents

A
37
Q

More reactive non-metals are stronger oxidizing agents

How can we check if the non-metal is more reactive than another?

A

A more reactive nonmetal
is able to oxidize
the ions of a less reactive
non-metal.

38
Q

Redox Titration

What is a titre?

A

The volume of the solution added from the burette to reach
equivalence

39
Q

Redox Titrations

What does the analysis of iron with manganate(VII) involve?

A

This redox titration uses KMnO4 in an acidic solution as the oxidizing agent, which
oxidizes Fe2+ ions to Fe3+, MnO4– is reduced to Mn2+,

40
Q

What does the reaction of iron with manganate(VII) result in?

A

Colour change from deep purple to colourless

41
Q

Redox Reaction

What is the full redox reaction of iron with manganate(VII)?

A

Page 420

42
Q

Redox Reaction

What does the iodine-thiosulfate reaction involve?

A

The reaction of excess iodide with an oxidizing agnet(KMnO4, KIO3, K2Cr2O7, NaOCl) to form iodine

43
Q

Redox Titrations

What happens to the liberated iodine molecules?

A

They are titrated against sodium thiosulfate using starch as indicator

44
Q

Redox Titrations

What are the half equations and full redox reaction of iodine and thiosulfate?

A

Page 421

45
Q

Redox Titrations

What happens to the blue color of the starch indicator?

A

It forms a blue color when it forms a complex awith I2, however this blue color disappears when is reduced to I–

46
Q

Redox Titration

Why is determining the dissolved oxygen quantity of water important?

A

As oxygen is essential to the survival of aquatic life. As the level of pollution in water increases, the dissolved oxygen content generally decreases

47
Q

Redox Titrations

What is the BOD

A

BOD is the quantity
of oxygen needed to
oxidize organic matter
in a sample of water
over a five-day period at
a specified temperature.

48
Q

Redox Titrations

What is the Winkler method?

A

A series of redox recations which helps determine quantity of dissolved oxygen in water

49
Q

Redox Titrations

What is the first step of the Winkler method?

A

The dissolved oxygen, O2(g), in the water is ‘fixed’ by the addition of amanganese(II) salt such as MnSO4. Reaction of this salt with O2 in basic solution causes oxidation of Mn(II) to higher oxidation states, such as Mn(IV). Page 423

50
Q

Redox Titrations

What is the second step of the Winkler method?

A

Acidified iodide ions, I–, are added to the solution, and are oxidized by the Mn(IV)
to I2

51
Q

Redox Titrations

What is the third step of the Winkler method?

A

The iodine produced is then titrated with sodium thiosulfate, or every 1 mole of O2 in the water, 4 mol of S2O32– are used

Chemistry Chapter 9 (2 decks)

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