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Chemistry NEET Questions — Free MCQ Practice

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${MnO}_{4}^{2 -}$ (1 mole ) in neutral aqueous medium is disproportionate to :

A.

2/3 mole of ${MnO}_{4}^{-}$ and 1/3 mole of ${MnO}_{2}$

B.

1/3 mole of ${MnO}_{4}^{-}$ and 2/3 mole of ${MnO}_{2}$

C.

1/3 mole of ${Mn}_{2} O_{7}$ and 1/3 mole of ${MnO}_{2}$

D.

2/3 mole of ${Mn}_{2} O_{7}$ and 1/3 mole of ${MnO}_{2}$

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Explanation

MnO2-4 in neutral aqueous medium is disproportionate to 2/3 mole of MnO-4 and 1/3 mole of MnO2.

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The oxidation number of phosphorus in $Ba {(H_{2} {PO}_{2})}_{2}$ is :

A.

-1

B.

+1

C.

+2

D.

+3

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Explanation

In the compound Ba(H2PO2)2, phosphorus is present in the oxidation state of +1. This can be determined by following the rules for assigning oxidation numbers, where the sum of oxidation numbers of all elements in a neutral compound is zero.

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If it is known that in ${Fe}_{0.96} O$ , Fe is present in +2 and +3 oxidation state. What is the mole fraction of ${Fe}^{2 +}$ in the compound ?

A.

12/25

B.

25/12

C.

1/12

D.

11/12

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Which ordering of compounds is according to the decreasing order of the oxidation state of nitrogen ?

A.

${HNO}_{3}, NO, {NH}_{4} Cl, N_{2}$

B.

${HNO}_{3}, NO, N_{2}, {NH}_{4} Cl$

C.

${HNO}_{3}, {NH}_{4} Cl, NO, N_{2}$

D.

$NO, {HNO}_{3}, {NH}_{4} Cl, N_{2}$

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Explanation

N is having Ox.no

5 ,2,0 , -3

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2 mole of $N_{2} H_{4}$ loses 16 mole of electron is being converted to a new compound X. Assuming that all of the N appears in the new compound. What is the oxidation state of 'N' in X ?

A.

-1

B.

-2

C.

+2

D.

+4

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Explanation

2 moles of N loses 16 moles of electron,so one N will lose 4 electron

it means oxid no should increase by +4 unit..

in N₂H₄

_{-2 +4 = 2}

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When $K_{2} {Cr}_{2} O_{7}$ is converted to $K_{2} {CrO}_{4}$ , the change in the oxidation state of chromium is :

A.

0

B.

6

C.

4

D.

3

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When a manganous salt is fused with a mixture of ${KNO}_{3}$ and solid NaOH, the oxidation number of Mn changes from +2 to :

A.

+4

B.

+3

C.

+6

D.

+7

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Explanation

Reaction involved:

M n O + N a O H + K N O_{3} \to N a_{2} M n O_{4} + K N O_{2} + H_{2} O

Assign the oxidation number to Mn as:

Let the oxidation number of Mn be 'x'.

Oxidation number of

N a = + 1, O = - 2

.

In

M n O

:

x + (- 2) = 0

x = + 2

In

N a_{2} M n O_{4}

:

2 \times 1 + x + 4 \times (- 2) = 0

x + 2 - 8 = 0

or

x = + 6

thus can be written as:

M +2 n O + N a O H + K N O_{3} \to N a_{2} M +6 n O_{4} + K N O_{2} + H_{2} O

When a manganous salt (MnO) is fused with a mixture of

K N O_{3}

and solid NaOH the oxidation number of Mn changes from +2 to +6.

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In $Fe (II) - {MnO}_{4}^{-}$ titration, ${HNO}_{3}$ , is not used because :

A.

it oxidises ${Mn}^{2 +}$

B.

it reduces ${MnO}_{4}^{-}$

C.

it oxidises ${Fe}^{2 +}$

D.

it reduces ${Fe}^{3 +}$ formed

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Explanation

3.

Nitric acid itself is a powerful oxidising agent, and so it will also react with and consume part of the oxalate ions. Therefore, in the presence of nitric acid, lesser amount of KMnO4 will be needed to reach the end poin

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Which species are oxidized and reduced in the reaction ?

${FeC}_{2} O_{4} + {KMnO}_{4} \to {Fe}^{3 +} + {CO}_{2} + {Mn}^{2 +}$

A.

Oxidised : Fe,C ; Reduced : Mn

B.

Oxidised : Fe; Reduced : Mn

C.

Reduced : Fe,Mn ; Oxidised : C

D.

Reduced : C; Oxidised : Mn,Fe

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Explanation

1.

oxidized

Fe goes from +2 to +3..

C goes from +3 (oxalate) to +4 (CO2)

reduced

Mn goes from +7 to +2

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In which of the following reactions, $H_{2} O_{2}$ is acting as a reducing agent ?

A.

${SO}_{2} + H_{2} O_{2} \to H_{2} {SO}_{4}$

B.

$2 KI + H_{2} O_{2} \to 2 KOH + I_{2}$

C.

$PbS + 4 H_{2} O_{2} \to {PbSO}_{4} + 4 H_{2} O$

D.

${Ag}_{2} O + H_{2} O_{2} \to 2 Ag + H_{2} O + O_{2}$

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Explanation

4.

O is going from -1 to zero , so getting oxidized ,so will act as R.A

Chemistry MCQs for NEET — Practice Questions with Answers

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