Redox Reactions Test

Result

Redox Reactions Test - 18

Score
-
out of -
Rank
-
out of -

TIME Taken - -

SHARING IS CARING

If our Website helped you a little, then kindly spread our voice using Social Networks. Spread our word to your readers, friends, teachers, students & all those close ones who deserve to know what you know now.

Weekly Quiz Competition

Question 1
1 / -0

Which reaction involves neither oxidation nor reduction?

A
$$CrO_{4}^{2-}\rightarrow Cr_{2}O_{7}^{2-}$$

B
$$Cr\rightarrow CrCl_{3}$$

C
$$Na\rightarrow Na^{+}$$

D
$$S_{2}O_{6}^{2-}\rightarrow S_{4}O_{6}^{2-}$$

Solution

Hint: If a species releases an electron, it is called oxidation and if a species accepts an electron, it is called reduction.

Step 1: Option A

$${CrO_4}^{2-}\rightarrow {Cr_2{O_7}^{2-}}$$

Here oxidation number of $$Cr$$ in $${CrO_4}^{2-}$$ is-

$$x+{(4\times{-2})}=-2$$, where $$x$$ is the oxidation number of $$Cr$$.

$$x=+6$$.

Oxidation number of $$Cr$$ in $${Cr_2O_7}^{2-}$$ is-

$$2x-14=-2$$

$$x=+6$$

So, there is no change in oxidation number. It does not undergo an oxidation or reduction reaction.

Step 2: Option B

$$Cr\rightarrow CrCl_3$$

Oxidation number of $$Cr$$ is $$0$$ and oxidation number of $$Cr$$ in $$CrCl_3$$ is

$$x-3=0$$, where $$x$$ is the oxidation number of $$Cr$$.

$$x=+3$$

Here $$Cr$$ releases three electrons to get converted to $$Cr^{+3}$$ and undergoes oxidation.

Step 3: Option C

$$Na\rightarrow Na^+$$

Here $$Na$$ converted to $$Na^+$$ by releasing an electron and undergoes oxidation.

Step 4: Option C

$${S_2O_6}^{2-}\rightarrow {S_4O_6}^{2-}$$

Oxidation number of $$S$$ in $${S_2O_6}^{2-}$$ is-

$$2y-12=-2$$ , where $$y$$ is the oxidation number of $$S$$.

$$y=+5$$

Oxidation number of $${S_4O_6}^{2-}$$ is-

$$4y-12=-2$$

$$y=2.5$$

So, here oxidation number decreases that means $$S$$ accepts electrons and undergoes reduction reaction.

Final Step: Correct option is $$(A)$$.
Question 2
1 / -0

The oxidation states of sulphur in the anions, $$SO_{3}^{2-}$$, $$S_{2}O_{4}^{2-}$$ and $$S_{2}O_{6}^{2-}$$ follow the order :

A
$$S_{2}O_{4}^{2-}$$<$$SO_{3}^{2-}$$<$$S_{2}O_{6}^{2-}$$

B
$$SO_{3}^{2-}$$< $$S_{2}O_{4}^{2-}$$< $$S_{2}O_{6}^{2-}$$

C
$$S_{2}O_{4}^{2-}$$< $$S_{2}O_{6}^{2-}$$<$$SO_{3}^{2-}$$

D
$$S_{2}O_{6}^{2-}$$<$$S_{2}O_{4}^{2-}$$<$$SO_{3}^{2-}$$

Solution

Sulphur in $$SO_{3}^{-2}, S_{2}O_{4}^{-2},$$ and $$ S_{2}O_{6}^{-2}$$ has $$+4$$, $$+3$$ and $$+5$$ oxidation state respectively.
Hence, the order is $$S_{2}O_{4}^{2-}$$<$$SO_{3}^{2-}$$<$$S_{2}O_{6}^{2-}$$.
Question 3
1 / -0

The oxidation state of the most electronegative atom in each of the product in the following reaction is
$$H_{2}+O_{2}\rightarrow H_{2}O_{2}+H_{2}O$$

A
$$-2,\: -2$$

B
$$+1,\:-2$$

C
$$+2,\:-1$$

D
$$-1,\:-2$$

Solution

In hydrogen peroxide, the oxidation number of O is $$-1$$ as it is a peroxide (O-O) while in water it is $$-2$$ as it is an oxide (O$$^{2-}$$).
Question 4
1 / -0

Which of the following is a redox reaction?

A
$$NaCl+KNO_{3}\rightarrow NaNO_{3}+KCl$$

B
$$CaC_{2}O_{4}+2HCl\rightarrow CaCl_{2}+H_{2}C_{2}O_{4}$$

C
$$Mg(OH)_{2}+2NH_{4}Cl\rightarrow MgCl_{2}+2NH_{4}OH$$

D
$$Zn+2AgCN\rightarrow 2Ag+Zn(CN)_{2}$$

Solution

$$Zn^{0}+2\mathrm{A}g^{+1}CN\rightarrow 2\mathrm{A}g^{0}+Zn^{+2}(CN)_{2}$$

Oxidation of Zn while reduction of Ag occurs.

Hence, it is a redox reaction.
Question 5
1 / -0

When ammonium nitrate is gently heated, an oxide of nitrogen is formed. What is the oxidation state of nitrogen in this oxide?

A
$$+4$$

B
$$+2$$

C
$$+3$$

D
$$+1$$

Solution

When ammonium nitrate is gently heated, dinitrogen monoxide $$N_2O$$ is obtained.
Let $$x$$ be the oxidation state of $$N$$ in $$N_2O$$.
The oxidation state of oxygen is $$-2$$.
The sum of the oxidation states for neutral molecule is $$0$$.
Hence, $$2x+(-2)=0$$ or, $$x=+1$$.
Therefore, the oxidation state of $$N$$ is $$+1$$.
Question 6
1 / -0

Iron shows least oxidation state in which of the following?

A
$$K_{4}[Fe(CN)_{6}]$$

B
$$K_{3}[Fe(CN)_{6}]$$

C
$$FeSO_{4}(NH_{4})_{2}SO_{4}(6H_{2}O)$$

D
$$Fe_{2}(CO)_{9}$$

Solution

The oxidation states of iron in $$K_4[Fe(CN)_6], \ K_3[Fe(CN)_6], \ FeSO_4(NH_4)_2SO_4(6H_2O) \ and \ Fe_2(CO)_9$$ are $$+2, \:+3,\: +2$$ and $$0 $$ respectively.
Hence, the least oxidation state of Fe is in $$Fe_2(CO)_9$$.
Question 7
1 / -0

In which one of the following compounds does oxygen have an oxidation number of $$+2$$?

A
$$F_{2}O$$

B
$$Cl_{2}O$$

C
$$Na_{2}O_{2}$$

D
$$Na_{2}O$$

Solution

Flourine is more electronegative than oxygen which in turn is more electronegative than Cl and Na.
The oxidation number of oxygen in $$F_2O, Cl_2O, Na_2O_2$$ and $$Na_2O$$ are $$+2, \:-2,\: -1$$ and $$-2$$ respectively.
Question 8
1 / -0

The oxidation number of $$Mn$$ in potassium permanganate is :

A
$$+6$$

B
$$+7$$

C
$$+5$$

D
$$+8$$

Solution

Let $$x$$ be the oxidation number of manganese in potassium permanganate. ($$KMnO_4$$)

The oxidation numbers of potassium and oxygen are $$+1$$ and $$-2$$ respectively.

The sum of the oxidation numbers in a neutral molecule is zero.

Hence, $$1+x+4(-2)=0$$ or, $$x=+7$$.
Question 9
1 / -0

In which of the following compounds, is the oxidation number of sulphur is the least?

A
$$SO_{2}$$

B
$$SO_{3}$$

C
$$Na_{2}S_{4}O_{8}$$

D
$$H_{2}SO_{4}$$

Solution

The oxidation number of sulphur in $$SO_2, \: SO_3,\: Na_2SO_4$$ and $$H_2SO_4$$ are $$+4,\: +6,\: +2.5$$ and $$+6$$ respectively. Hence, it is least in $$Na_2SO_4$$.
Question 10
1 / -0

Which of the following does not involve the change of valency?

A
$$SO_{2}+2H_{2}S\rightarrow 2H_{2}O+2S$$

B
$$2Na+O_{2}\rightarrow Na_{2}O_{2}$$

C
$$Na_{2}O_{2}+H_{2}SO_{4}\rightarrow Na_{2}SO_{4}+H_{2}O_{2}$$

D
$$Zn+CuSO_{4}\rightarrow ZnSO_{4}+Cu$$

Solution

The reaction between sodium peroxide and sulphuric acid to obtain sodium sulphate and hydrogen peroxide is a double displacement reaction in which the cations switch positions. Hence, there is no change in valency in this reaction.

User

Question Analysis

Correct -
Wrong -
Skipped -

My Perfomance

Score
-
out of -
Rank
-
out of -

Re-Attempt Weekly Quiz Competition

Redox Reactions Test - 18

Result

Redox Reactions Test - 18

Score

-

Rank

-

SHARING IS CARING

Question 1

$$CrO_{4}^{2-}\rightarrow Cr_{2}O_{7}^{2-}$$

$$Cr\rightarrow CrCl_{3}$$

$$Na\rightarrow Na^{+}$$

$$S_{2}O_{6}^{2-}\rightarrow S_{4}O_{6}^{2-}$$

Solution

Question 2

$$S_{2}O_{4}^{2-}$$<$$SO_{3}^{2-}$$<$$S_{2}O_{6}^{2-}$$

$$SO_{3}^{2-}$$< $$S_{2}O_{4}^{2-}$$< $$S_{2}O_{6}^{2-}$$

$$S_{2}O_{4}^{2-}$$< $$S_{2}O_{6}^{2-}$$<$$SO_{3}^{2-}$$

$$S_{2}O_{6}^{2-}$$<$$S_{2}O_{4}^{2-}$$<$$SO_{3}^{2-}$$

Solution

Question 3

$$-2,\: -2$$

$$+1,\:-2$$

$$+2,\:-1$$

$$-1,\:-2$$

Solution

Question 4

$$NaCl+KNO_{3}\rightarrow NaNO_{3}+KCl$$

$$CaC_{2}O_{4}+2HCl\rightarrow CaCl_{2}+H_{2}C_{2}O_{4}$$

$$Mg(OH)_{2}+2NH_{4}Cl\rightarrow MgCl_{2}+2NH_{4}OH$$

$$Zn+2AgCN\rightarrow 2Ag+Zn(CN)_{2}$$

Solution

Question 5

$$+4$$

$$+2$$

$$+3$$

$$+1$$

Solution

Question 6

$$K_{4}[Fe(CN)_{6}]$$

$$K_{3}[Fe(CN)_{6}]$$

$$FeSO_{4}(NH_{4})_{2}SO_{4}(6H_{2}O)$$

$$Fe_{2}(CO)_{9}$$

Solution

Question 7

$$F_{2}O$$

$$Cl_{2}O$$

$$Na_{2}O_{2}$$

$$Na_{2}O$$

Solution

Question 8

$$+6$$

$$+7$$

$$+5$$

$$+8$$

Solution

Question 9

$$SO_{2}$$

$$SO_{3}$$

$$Na_{2}S_{4}O_{8}$$

$$H_{2}SO_{4}$$

Solution

Question 10

$$SO_{2}+2H_{2}S\rightarrow 2H_{2}O+2S$$

$$2Na+O_{2}\rightarrow Na_{2}O_{2}$$

$$Na_{2}O_{2}+H_{2}SO_{4}\rightarrow Na_{2}SO_{4}+H_{2}O_{2}$$

$$Zn+CuSO_{4}\rightarrow ZnSO_{4}+Cu$$

Solution

User

Question Analysis

My Perfomance

Score

-

Rank

-

Results Announcement on: coming Monday

Stay Tuned: We’ll update you on your result via email or SMS.