Redox Reactions Test

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Redox Reactions Test - 3

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Weekly Quiz Competition

Question 1
1 / -0

The oxidation number of oxygen in most compounds is

A
1

B
-2

C
-3

D
4

Solution

Oxygen is the most electronegative element. Oxygen have 6 electrons in its outermost shell and to gain noble gas configuration oxygen have to take 2 more electrons.
Question 2
1 / -0

Aurous chloride and auric chloride are written as Au(l)Cl and Au(lll)Cl₃.The roman numeral in parenthesis after the symbol of the metal in the molecular formula represents the

A
basic character

B
oxidation number

C
electronegativity

D
Ionic state

Solution

The roman number represents the oxidation number/oxidation state of an element.It is popularly known as Stock notation given by the german scientist Alfred stock.
Question 3
1 / -0

Both CO₂ and H₂ gases are

A
colourless

B
heavier than air

C
acidic in nature

D
soluble in water

Solution

colourless
Question 4
1 / -0

All combustion reactions, which make use of elemental dioxygen, as well as other reactions involving elements other than dioxygen are:

A
decomposition reactions

B
displacement reactions

C
disproportionation reactions

D
Combination reaction

Solution

A combination reaction (also known as a synthesis reaction) is a reaction where two or more elements or compounds (reactants) combine to form a single compound (product). Such reactions may be represented by equations of the following form: X + Y → XY.
Question 5
1 / -0

Which of the following gases can be used for storage of fresh sample of oil for a long time?

A
Nitrogen or helium

B
Helium or oxygen

C
Carbon dioxide or oxygen

D
Nitrogen or oxygen

Solution

Nitrogen or helium
Question 6
1 / -0

The electrolytic decomposition of water gives H₂ and O₂ in the ratio of

A
1 : 2 by volume

B
8 : 1 by mass

C
2 : 1 by volume

D
1 : 2 by mass

Solution

2 : 1 by volume
Question 7
1 / -0

Displacement of hydrogen from cold water is done by

A
superoxides

B
all alkaline earth metals

C
all alkali metals

D
all transition elements

Solution

A common characteristic of most Alkali metal is their ability to displace H₂(g) from water. This is represented by their large, negative electrode potentials. In this event, the Group 1 metal is oxidized to its metal ion and water is reduced to form hydrogen gas and hydroxide ions. The general reaction of an alkali metal (M) with H₂O (l) is given in the following equation:

2M(s)+2H2O(l)⟶2M+(aq)+2OH−(aq)+H2(g)

From this reaction it is apparent that OH^- is produced, creating a basic or alkaline environment. Group 1 elements are called alkali metals because of their ability to displace H₂(g) from water and create a basic solution.Alkali metals are also known to react violently and explosively with water. This is because enough heat is given off during the exothermic reaction to ignite the H₂(g).
Question 8
1 / -0

Fractional Oxidation Number exists because

A
the average oxidation state of the element is divided by two

B
electrons are never shared/transferred in that element

C
middle carbon in such elements has always zero oxidation state

D
the element is present in different oxidation states
Solution
The oxidation states are usually in whole numbers, but in some cases, they are in fractional numbers. Consider Fe₃O₄.
- Using rule #2, the sum of the oxidation state of all atoms is 0
- Using rule #6, the O has the oxidation state of -2. 4x(-2) = -8
- Equation: 3Fe + (-8) = 0
- 3Fe = 8
- Fe = 8/3
In most cases, atoms of the same element in a given compound have the same oxidation states, but each atom can have a different state than the other. For Fe₃O₄, two Fe atoms have an oxidation state of +3 and one of +2, which makes the total oxidation state of Fe= 8/3.

Instead of averaging the oxidation states, we must keep them separated. This is called fragmenting, which occurs if there is an ionic compound, and the ions can be separated. The oxidation state of the individual atoms in the different ions can be determined.
Question 9
1 / -0

The strength of a reductant/oxidant in redox systems can be determined

A
by taking into consideration only half reactions involving oxidation

B
by the titration method using a redox sensitive indicator

C
by taking into consideration the different oxidation states of the atom in the element

D
by taking into consideration only half reactions involving reduction

Solution

Because a redox indicator (also called an oxidation-reduction indicator) is an indicator which undergoes a definite color change at a specific electrode potential.
Question 10
1 / -0

One of the following has application in electrode processes and cells

A
the concept of redox reactions

B
the different oxidation states of the atom in the element

C
half reactions involving reduction

D
half reactions involving oxidation

Solution

The concept of redox reaction is used in electrode processes and cells. Because in these processes an electrode loose or gain electrons, electrode with higher reduction potential undergo reduction, electrode potential is given a positive sign if oxidation occures at the electrode.

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Re-Attempt Weekly Quiz Competition

Redox Reactions Test - 3

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Redox Reactions Test - 3

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SHARING IS CARING

Question 1

1

-2

-3

4

Solution

Question 2

basic character

oxidation number

electronegativity

Ionic state

Solution

Question 3

colourless

heavier than air

acidic in nature

soluble in water

Solution

Question 4

decomposition reactions

displacement reactions

disproportionation reactions

Combination reaction

Solution

Question 5

Nitrogen or helium

Helium or oxygen

Carbon dioxide or oxygen

Nitrogen or oxygen

Solution

Question 6

1 : 2 by volume

8 : 1 by mass

2 : 1 by volume

1 : 2 by mass

Solution

Question 7

superoxides

all alkaline earth metals

all alkali metals

all transition elements

Solution

Question 8

the average oxidation state of the element is divided by two

electrons are never shared/transferred in that element

middle carbon in such elements has always zero oxidation state

the element is present in different oxidation states

Solution

Question 9

by taking into consideration only half reactions involving oxidation

by the titration method using a redox sensitive indicator

by taking into consideration the different oxidation states of the atom in the element

by taking into consideration only half reactions involving reduction

Solution

Question 10

the concept of redox reactions

the different oxidation states of the atom in the element

half reactions involving reduction

half reactions involving oxidation

Solution

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