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Which is chlorate (I) ion?
a)
b)
c)
d)
Correct answer is option 'B'. Can you explain this answer?

Pooja Shah answered
  • ClO3- : A very reactive inorganic anion.
  • The term chlorate can also be used to describe any compound containing the chlorate ion, normally chlorate salts. 
  • Example: Potassium chlorate, KClO3

Which of the following is not an example of redox reaction?
  • a)
    BaCl2 + H2SO4 ⎯→ BaSO4 + 2HCl
  • b)
    Fe2O3 + 3CO ⎯→ 2Fe + 3CO2
  • c)
    2K + F2 ⎯→ 2KF
  • d)
    CuO + H2 ⎯→ Cu + H2O
Correct answer is option 'A'. Can you explain this answer?

Raghav Bansal answered
a) BaCl2 + H2SO4 → BaSO4 + 2HCl is not a redox reaction, as there is no change in the oxidation state of any element.
It is an example of double displacement reactions.

The oxidation half reaction for following reaction is
Fe2+(aq) + Cr2O72-(aq) → Fe3+ (aq) + Cr3+(aq)
  • a)
    Fe3+(aq) → Fe2+ (aq)
  • b)
    Cr2O72-(aq) → Cr3+(aq)
  • c)
    Cr3+(aq) → Cr2O72-(aq)
  • d)
    Fe2+ (aq) → Fe3+(aq)
Correct answer is option 'D'. Can you explain this answer?

Geetika Shah answered
Oxidation half reaction for a reaction is that reaction which gives us the reactant and product formed after the oxidation of the reactant. In this case Fe+2 oxidizes itself to Fe+3 and so the oxidation of Fe+2 is oxidation half reaction. Option d correct.

Oxidation numbers of P in PO4−3, of S in SO42− and that of Cr in Cr2O72− are respectively,
  • a)
     +5, +6 and +6
  • b)
    +3, +6 and +5
  • c)
    +5, +3 and +6               
  • d)
    -3, +6 and +6
Correct answer is option 'A'. Can you explain this answer?

Raghav Bansal answered
The correct answer is option A
(I) xPO43−​ ⇒ x + 4 × (−2) = −3
                ⇒x = −3 + 8 = +5
                ⇒x = +5
Oxidation number of P = +5
(II) xSO42−​ ⇒ x + 4 × (−2) = −2
                ⇒x = −2 + 8
                  ⇒x = +6
Oxidation number of S=+6
(III) xCr2​O72− ​    ⇒2x + 7 × (−2) = −2
                        ⇒2x =−2+14
                        ⇒2x=12
                        ⇒x= 12/2​ = +6

In Daniel cell, oxidation takes place at
  • a)
    Any of the two electrodes
  • b)
    Depends on the salts and their solutions
  • c)
    Anode
  • d)
    Cathode
Correct answer is option 'C'. Can you explain this answer?

Rohit Shah answered
The solutions in which the electrodes are immersed are called electrolytes. The chemical reaction that takes place in a galvanic cell is the redox reaction. One electrode acts as anode in which oxidation takes place and the other acts as the cathode in which reduction takes place.

Hydrogen is prepared from H2O by adding
  • a)
    Ag, which acts as reducing agent
  • b)
    Ca, which acts as reducing agent
  • c)
    Au, which acts as oxidising agent
  • d)
    AI, which acts as oxidising agent
Correct answer is option 'B'. Can you explain this answer?

Saumya Dey answered
Preparation of Hydrogen from Water

- Hydrogen gas can be prepared from water by using a reducing agent, which reduces water to hydrogen gas and also gets oxidized in the process.
- Calcium (Ca) is a good reducing agent and can be used to prepare hydrogen gas from water.
- When calcium is added to water, it reacts with water to form calcium hydroxide and hydrogen gas.
- The chemical equation for the reaction is:

Ca + 2H2O → Ca(OH)2 + H2

- Calcium has a strong affinity for oxygen and readily reacts with water to form calcium hydroxide, liberating hydrogen gas.
- This reaction is exothermic and produces a considerable amount of heat, which can be used to heat water or other substances.
- The liberated hydrogen gas can be collected by upward displacement of air or by using a gas syringe or gas jar.
- The purity of hydrogen gas prepared by this method is relatively low, as it may contain impurities like calcium hydroxide, unreacted water, and other gases like nitrogen and oxygen.
- Therefore, additional purification steps may be required to obtain pure hydrogen gas.

Advantages of using Calcium as a reducing agent

- Calcium is a readily available and inexpensive reducing agent.
- It reacts readily with water, producing a large amount of hydrogen gas.
- The reaction is exothermic and produces heat, which can be utilized in other processes.
- Calcium is a relatively safe reducing agent, as it does not react violently with water or other substances.
- The by-products of the reaction, calcium hydroxide, and hydrogen gas, are non-toxic and can be disposed of safely.

The reduction potential values of M, N and O are +2.46, -1.13 and -3.13 V respectively. Which of the following order is correct regarding their reducing property?
  • a)
    M>N>O
  • b)
    O>M>N
  • c)
    M>O>N
  • d)
    O>N>M
Correct answer is option 'D'. Can you explain this answer?

Geetika Shah answered
Reduction potential means the tendency to reduce itself, i.e SO if we need reducing agent, then we need elements having more oxidising potential or reversing reduction potential order.
The order of reduction potential - O < N < M
So the order of reducing agent = M < N < O

Oxidation numbers of P in PO43– , of S in SO42– and that of Cr in Cr2O72–  are respectively [2009]
  • a)
    + 3, + 6 and + 5
  • b)
    + 5, + 3 and + 6
  • c)
    – 3, + 6 and + 6
  • d)
    + 5, + 6 and + 6
Correct answer is option 'D'. Can you explain this answer?

Hansa Sharma answered
(i) Sum of oxidation states of all atoms = charge of ion.
(ii) oxidation number of oxygen = -2
Let the oxidation state of P in PO43- is x.
 PO43- 

x + 4 (-2) = - 3
x-8 = - 3
x = +5

Let the oxidation state of S in SO42- is y
y + 4(-2) = -2
y-8 = - 2
y = +6

Let the oxidation state of Cr in Cr2O72- is z.
2 x z+7(-2) = -2
2z-14 = - 2
z=+6
Hence, oxidation state of P, S and Cr are +5, +6 and +6

Which of the following involves a redox reaction?
  • a)
    Reaction of H2SO4 with NaOH
  • b)
    Production of ozone from oxygen in the atmosphere by lightning
  • c)
    Production of nitrogen oxides from nitrogen and oxygen in the atmosphere by lightning
  • d)
    Evaporation of water
Correct answer is option 'C'. Can you explain this answer?

Rocky Handsome answered
•The 1st reaction is acid base reaction which does not involve either oxidation or reduction.

•O3 formation from O2 does not involve either oxidation or reduction.

•Nitrogen oxides from N2 and O2 involves oxidation of nitrogen and reduction of oxygen.

For example, N2 + O2---> NO2.
• Evaporation of H2O is a physical change and is not a chemical change.

Hence answer is C.

Select the set of compounds with oxidation-reduction duality.
  • a)
    Cl2, H3PO4, HCHO, HNO2
  • b)
    Cl2, H3PO3, C6H5CHO, H2O2
  • c)
    Br2, H3PO2, CH3CHO, H3PO4
  • d)
    CrO2Cl2, KMnO4, SO3, CO2
Correct answer is option 'B'. Can you explain this answer?

Neha Sharma answered
Com pounds having oxidising and reducing nature in given reaction are said to have oxidation-reduction duality. Such compounds are said to undergo disproportionation reaction.



(This is called Cannizzaro reaction.)

Note Such compounds have O.N. of the affected atoms intermediate of oxidation part and reduction part

In the following questions a statement of assertion (A) followed by a statement of reason (R) is given. Choose the correct option out of the choices given below each question. 
Assertion(A): Among halogens fluorine is the best oxidant.
Reason(R): Fluorine is the most electronegative atom.
  • a)
    Both A and R are true and R is the correct explanation of A.
  • b)
    Both A and R are true and R is not the correct explanation of A.
  • c)
    Both A and R are false.
  • d)
    A is true but R is false.
Correct answer is option 'B'. Can you explain this answer?

Dhruba Patel answered
Assertion(A): Among halogens fluorine is the best oxidant.
Reason(R): Fluorine is the most electronegative atom.

The correct answer is option B: Both A and R are true and R is not the correct explanation of A.

Explanation:
Assertion:
Fluorine is the best oxidant among halogens. An oxidant is a substance that accepts electrons from another substance during a chemical reaction. Fluorine has a high tendency to gain one electron to achieve a stable electron configuration, making it a strong oxidant.

Reason:
Fluorine is the most electronegative atom. Electronegativity is the measure of an atom's ability to attract electrons towards itself in a chemical bond. Fluorine has the highest electronegativity value among all the elements, indicating its strong ability to attract electrons. This high electronegativity makes fluorine highly reactive and a strong oxidant.

Explanation of the Correct Answer:
Both the assertion and reason are true. Fluorine is indeed the best oxidant among halogens due to its high tendency to gain electrons. Additionally, fluorine is the most electronegative atom, which explains its strong oxidizing power. However, the reason provided does not directly explain why fluorine is the best oxidant among halogens. Other factors such as atomic size and electron shielding also play a role in determining the oxidizing power of halogens. Therefore, the reason is not the correct explanation of the assertion.

In conclusion, fluorine's high electronegativity and strong tendency to gain electrons make it the best oxidant among halogens. However, its status as the best oxidant cannot be solely attributed to its electronegativity.

The oxidation number of oxygen in most compounds is
  • a)
    -3
  • b)
    1
  • c)
    4
  • d)
    -2.0
Correct answer is option 'D'. Can you explain this answer?

Niharika Nair answered
Oxidation number of oxygen in most compounds is -2.

Explanation:
- Oxidation number is the number assigned to an atom to indicate its degree of oxidation or loss/gain of electrons.
- Oxygen is a highly electronegative element, meaning it has a strong tendency to attract electrons.
- In most compounds, oxygen has an oxidation number of -2 because it tends to gain electrons to achieve a stable octet configuration (8 valence electrons).
- For example, in water (H2O), each hydrogen atom has an oxidation number of +1 and the oxygen atom has an oxidation number of -2, which balances out the charge to zero.
- There are some exceptions to this rule, such as in peroxides where oxygen has an oxidation number of -1, and in compounds with more electronegative elements where oxygen may have a positive oxidation number.
- Overall, the oxidation number of oxygen in most compounds is -2.

The oxidation number of chromium in potassium dichromate is [1995]
  • a)
    + 6
  • b)
    – 5
  • c)
    – 2
  • d)
    + 2
Correct answer is option 'A'. Can you explain this answer?

Ayush Sengupta answered
Let x = oxidation no. of Cr in K2Cr2O7.
∴ (2 × 1) + (2 × x) + 7 (– 2) = 0
or 2 + 2x – 14  = 0 or x = + 6.

Equivalent weight of H3PO2 in a reaction is found to be half of its molecular weight. It can be due to its
  • a)
    reaction of two H+ ion
  • b)
    oxidation of H3PO3
  • c)
    oxidation of H3PO4
  • d)
    reduction of PH3
Correct answer is option 'B'. Can you explain this answer?

Anisha Chauhan answered
An equivalent weight of H3PO2 when it disproportionates into PH3 and H3PO3 is
For disproportionation reactions, use a trick to find equivalent mass; E = E1 + E2; where E1 and E2 are equivalent masses of oxidation and reduction half-reactions of the same element.
Now, find the n-factor(total change in oxidation number per molecule) and then equivalent mass = molar mass/n-factor.
So, when H3PO2 changes into PH3, the oxidation state of phosphorous changes from +1 to -3 so as n-factor is 4. Also when H3PO2 changes into H3PO3, the oxidation state of phosphorous changes from +1 to +5 so as n-factor is again 4.
Now equivalent mass of H3PO2, E =(M/4) + (M/4) = M/2
Hence, the correct option is b.

Phosphorus has the oxidation state of + 3 in
  • a)
    Phosphorous acid [1994]
  • b)
    Orthophosphoric acid
  • c)
    Hypophosphorous acid
  • d)
    Metaphosphoric acid.
Correct answer is option 'A'. Can you explain this answer?

Sushant Goyal answered
O.N. of P in H3PO3 (phosphorous acid) 3 × 1 + x + 3 × (– 2) = 0 or x = + 3 In orthophosphoric acid (H3PO4) O.N. of P is + 5, in hypophosphorous acid (H3PO2) it is + 1 while in metaphosphoric acid (HPO3), it is + 5,

 In this method, the two half equations are balanced separately and then added together to give balanced equation
  • a)
    Reluctant method
  • b)
    Oxidizing agent method
  • c)
    Reducing agent method
  • d)
    Half reaction method
Correct answer is option 'D'. Can you explain this answer?

Kavita Joshi answered
In the ion-electron method (also called the half-reaction method), the redox equation is separated into two half-equations - one for oxidation and one for reduction. Each of these half-reactions is balanced separately and then combined to give the balanced redox equation.

Intensity of blue colour increases gradually when _________________
  • a)
    copper rod is dipped in silver nitrate solution
  • b)
    silver rod is dipped in copper nitrate solution
  • c)
    zinc rod is dipped in silver solution
  • d)
    copper rod is dipped in zinc rod solution
Correct answer is option 'A'. Can you explain this answer?

EduRev NEET answered
When a copper rod is dipped in silver nitrate solution, a redox reaction occurs between Copper and an aqueous solution of silver nitrate.
  • So the intensity of blue colour increases gradually as silver deposits on the rod.

Reduction is defined in terms of
I. electronation and hydrogenation
II. deelectronation and gain of oxygen
III. increase in oxidation number
IV. decrease in oxidation number
Select the correct terms
  • a)
    I and IV
  • b)
    I and III
  • c)
    II and II
  • d)
    I and II
Correct answer is option 'A'. Can you explain this answer?

Siddharth Mehra answered
Reduction is defined in terms of electronation and hydrogenation

Reduction is a chemical process that involves the gain of electrons or a decrease in oxidation number. It can be defined in terms of two main reactions: electronation and hydrogenation.

I. Electronation:
- Electronation refers to the process of gaining electrons. In a reduction reaction, a molecule, ion, or atom accepts one or more electrons, resulting in a more negative charge.
- For example, in the reaction: X + e- -> X-, the atom X gains an electron, and its oxidation number decreases. This is a reduction reaction.

II. Hydrogenation:
- Hydrogenation is a specific type of reduction reaction where hydrogen atoms are added to a molecule.
- During hydrogenation, the molecule gains hydrogen atoms, and its oxidation number decreases. This is a reduction reaction.
- For example, in the reaction: X + H2 -> XH2, the molecule X gains hydrogen atoms, and its oxidation number decreases. This is a reduction reaction.

III. Increase in oxidation number:
- Increase in oxidation number is not associated with reduction but with oxidation.
- In oxidation, the oxidation number of an atom, ion, or molecule increases, indicating the loss of electrons.
- Reduction, on the other hand, involves the gain of electrons, resulting in a decrease in oxidation number.

IV. Decrease in oxidation number:
- Decrease in oxidation number is directly associated with reduction.
- Reduction reactions involve the gain of electrons, leading to a decrease in oxidation number.
- For example, if the oxidation number of an atom changes from +2 to 0, it has undergone reduction because its oxidation number has decreased.

Conclusion:
Based on the definitions of reduction and the given options, the correct terms that define reduction are I. electronation and IV. decrease in oxidation number. These two terms accurately describe the process of reduction, where electrons are gained and the oxidation number decreases. Therefore, option A. (I and IV) is the correct answer.

The correct order of N-compounds in its decreasing order of oxidation states is
  • a)
    HNO3, NO, N2, NH4Cl
  • b)
    HNO3, NO, NH4Cl, N2
  • c)
    HNO3, NH4Cl, NO, N2
  • d)
    NH4Cl, N2, NO, HN03
Correct answer is option 'A'. Can you explain this answer?

Infinity Academy answered
To determine the decreasing order of oxidation states of nitrogen in the given compounds, we need to find the oxidation state of nitrogen in each compound:
  1. HNO3 (Nitric acid): Oxidation state of nitrogen: +5
  2. NO (Nitric oxide): Oxidation state of nitrogen: +2
  3. N2 (Dinitrogen): Oxidation state of nitrogen: 0
  4. NH4Cl (Ammonium chloride): Oxidation state of nitrogen: -3
Now, let's arrange these compounds in decreasing order of oxidation states:
  • HNO3: +5
  • NO: +2
  • N2: 0
  • NH4Cl: -3
So, the correct order in decreasing oxidation state is:
HNO3, NO, N2, NH4Cl

Direction: In the following questions, a statement of assertion (A) followed by a statement of Reason (R) is given. Choose the correct option out of the choices given below each question.
Assertion (A) : Redox couple is the combination of oxidised and reduced form of a substance involved in an oxidation or reduction half cell.
Reason (R) : In the representation EOFe3+ /Fe2+ and EO Cu2+/Cu, Fe3+/ Fe2+ and Cu2+ / Cu are redox couples.
  • a)
    Both A and R are true and R is the correct explanation of A.
  • b)
    Both A and R are true but R is not the correct explanation of A.
  • c)
    A is true but R is false.
  • d)
    Both A and R are false.
Correct answer is option 'A'. Can you explain this answer?

Geetika Shah answered
A redox couple is defined as pair of compounds or elements having together the oxidised and reduced forms of it and taking part in an oxidation or reduction half-reaction. So, Fe3+/Fe2+and Cu2+/Cu are redox couples.
Both assertion and reason are true reason is the correct explanation of assertion.

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