Redox Reactions Test

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Redox Reactions Test - 5

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Question 1
1 / -0

2 Na(s) -----------> 2Na⁺ + 2e^-

2H⁺+ 2 e^- --------> H₂

Which is oxidizing and Reducing?

A
electronegativity of sodium determines the direction of the reaction

B
sodium is oxidised and hydrogen is reduced

C
sodium is reduced

D
hydrogen is oxidised

Solution

Oxidation is a process in which one or more electrons are lost and oxidation number is increased. Sodium has 0 oxidation state as reactant and +1 oxidation state as product.

Similarly, Reduction is a process in which one or more electrons are gained and oxidation number is reduced i.e. from +1 to 0.
Question 2
1 / -0

In the free or the uncombined state, each atom in O₂O₃,P_4,S₈ and Mg has the oxidation number

A
zero

B
two

C
three

D
seven

Solution

In free or uncombined state each element has zero oxidation state.
Question 3
1 / -0

For ions composed of only one atom, the oxidation number is equal to the

A
always +1

B
charge on the ion

C
always -1

D
sum of different oxidation states

Solution

By definition, the oxidation number of an atom is the charge that atom would have if the compound was composed of ions.

The oxidation number of simple ions is equal to the charge on the ion. The oxidation number of sodium in the Na⁺ ion is +1, for example, and the oxidation number of chlorine in the Cl^- ion is -1.
Question 4
1 / -0

In the decomposition of lead (II) nitrate to give lead (II) oxide, nitrogen dioxide and oxygen gas, the coefficient of nitrogen dioxide (in the balanced equation) is

A
1

B
2

C
3

D
4
Question 5
1 / -0

Silver article turns black when kept in the open for a few days due to formation of

A
H₂S

B
AgSO₄

C
AgS

D
Ag₂S

Solution

Ag₂S
Question 6
1 / -0

An oxidation number of +1 is found in all their compounds of one of the below given options

A
superoxides

B
all transition elements

C
all alkali metals

D
all alkaline earth metals

Solution

The alkali metals (Group 1) have 1 valence electron. Alkali metals looses this electron to achieve noble gas configuration, and so alkali metals have oxidation number +1.
Question 7
1 / -0

The oxidation number of hydrogen in LiH, NaH and CaH₇is

A
-1

B
1and 2

C
-1 and -2

D
-2

Solution

This is according to the rules of assigning oxidation number i.e.

Metal hydrides, such as NaH, LiH, etc., in which the oxidation state for H is -1.
Question 8
1 / -0

Chlorine, bromine and iodine when combined with oxygen, have oxidation numbers

A
-2

B
-1

C
+1 or any positive number

D
-1 or any negative number

Solution

This is according to the rules of assigning oxidation number i.e.

Chlorine, Bromine, Iodine have positive oxidation numbers when combined with oxygen, for example in oxoacids and oxoanions.
Question 9
1 / -0

The oxidation number of an element in a compound is evaluated on the basis of certain rules. Which of the following rules is not correct in this respect?

A
In all its compounds, the oxidation number of fluorine is – 1.

B
The algebraic sum of all the oxidation numbers in a compound is zero.

C
The oxidation number of hydrogen is always +1.

D
An element in the free or the uncombined state bears oxidation number zero.

Solution

Normally hydrogen's oxidation number is +1, except for when it is part of a binary compound (2 elements) along with a metal. For example, LiH, NaH, CaH₂, all have hydrogen with oxidation number -1.
Question 10
1 / -0

Using the standard electrode potential of redox couples given below find out which of the following is the strongest oxidising agent.

E⁰ values: Fe³⁺/Fe²⁺= +0.77; I²/I^-(s)= +0.54; Cu²⁺/Cu= +0.34; Ag⁺/Ag= +0.80

A
Cu²⁺

B
I₂(s)

C
Fe³⁺

D
Ag⁺

Solution

The more positive the value of E⁰, the greater is the tendency of the species to get reduced, therefore Ag⁺/Ag= +0.80 is strongest oxidising agent.

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Re-Attempt Weekly Quiz Competition

Redox Reactions Test - 5

Result

Redox Reactions Test - 5

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SHARING IS CARING

Question 1

electronegativity of sodium determines the direction of the reaction

sodium is oxidised and hydrogen is reduced

sodium is reduced

hydrogen is oxidised

Solution

Question 2

zero

two

three

seven

Solution

Question 3

always +1

charge on the ion

always -1

sum of different oxidation states

Solution

Question 4

1

2

3

4

Question 5

H2S

AgSO4

AgS

Ag2S

Solution

Question 6

superoxides

all transition elements

all alkali metals

all alkaline earth metals

Solution

Question 7

-1

1and 2

-1 and -2

-2

Solution

Question 8

-2

-1

+1 or any positive number

-1 or any negative number

Solution

Question 9

In all its compounds, the oxidation number of fluorine is – 1.

The algebraic sum of all the oxidation numbers in a compound is zero.

The oxidation number of hydrogen is always +1.

An element in the free or the uncombined state bears oxidation number zero.

Solution

Question 10

Cu2+

I2(s)

Fe3+

Ag+

Solution

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H₂S

AgSO₄

Ag₂S

Cu²⁺

I₂(s)

Fe³⁺

Ag⁺