NEET
Practice Test 8
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DIRECTION : These are Assertion-Reason type question. Question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer the question from the following four options.

Statement-1:In a reaction
Zn(s) + CuSO4 (aq) ⟶ ZnSO4(aq) + Cu(s)
Zn is a reductant but itself get oxidized.
Statement-2 : In a redox reaction, oxidant is reduced by accepting electrons and reductant is oxidized by losing electrons.

  • Solution

DIRECTION : These are Assertion-Reason type question. Question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer the question from the following four options.

Statement-1: HClO4 is a stronger acid than HClO3.
Statement-2 :Oxidation state of Cl in HClO4 is +VII and in HClO3 +V

  • Solution

    Both statement-1 and statement-2 are true but reason is not the correct explanation of assertion. Greater the number of negative atoms present in the oxy-acid make the acid stronger. In general, the strengths of acids that have general formula (HO)mZOn can be related to the value of n. As the value of n increases, acidic character also increases. The negative atoms draw electrons away from the Z-atom and make it more positive. The Z-atom, therefore, becomes more effective in withdrawing electron density away from the oxygen atom that bonded to hydrogen. In turn, the electrons of H – O bond are drawn more strongly away from the H-atom. The net effect makes it easier from the proton release and increases the acid a strength.

DIRECTION : These are Assertion-Reason type question. Question contains two statements:Statement-1 (Assertion) and Statement-2 (Reason). Answer the question from the following four options.

Statement-1 :Stannous chloride is a powerful oxidising agent which oxidises mercuric chloride to mercury.
Statement-2 :Stannous chloride gives grey precipitate with mercuric chloride, but stannic chloride does not do so.

  • Solution

    Here, statement-1 is false, because stannous chloride is a strong reducing agent not strong oxidising agent.Stannous chlorides gives Grey precipitate with mercuric chloride. Hence statement-2 is true.

Consider the following reaction :

x\(MnO_{4}^{-}\) + y\(C_{2}O_{4}^{2-}\) + zH\(C_{2}O_{4}^{2-}\) ⟶ xMn2+ + 2yCO+ + \(\frac{Z}{2}\) H2O

The value’s of x, y and z in the reaction are, respectively :

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For H3PO3 and H3PO4 the correct choice is

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The standard reduction potential values of three metallic cations, X, Y and Z are 0.52,– 3.03 and – 1.18 V respectively.The order of reducing power of the corresponding metals is

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    More negative or lower is the reduction potential , more is the reducing property. Thus the reducing power of the corresponding metal will follow the reverse order,i.e. Y > Z > X.

Which of the following is a redox reaction?

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Oxidation numbers of Pin \(PO_{4}^{3-}\), of S in \(SO_{4}^{2-}\) and that of Cr in \(Cr_{2}O_{7}^{2-}\) are respectively

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    \(PO_{4}^{3-}\) = x + 4 (– 2) = – 3; x– 8= – 3; x= + 5
    \(SO_{4}^{2-}\) = x + 4 (–2) = – 2; x– 8= – 2; x= + 6
    \(Cr_{2}O_{7}^{2-}\) = 2x + 7 (–2) = – 2; 2x– 14 = –2;
    2x = 12 ; x = + 6

  • Solution

    \(SO_{3}^{2-}\) ⟶ S is in + 4 oxidation state
    \(S_{2}O_{4}^{2-}\) ⟶ S is in + 3 oxidation state
    \(S_{2}O_{6}^{2-}\) ⟶ S is in + 5 oxidation state

Zn gives H2 gas with H2SO4 and HCl but not with HNO3 because

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    Zinc gives H2 gas with dil H2SO4/HCl but not with HNO3 because in HNO3, \(NO_{3}^{-}\) ion is reduced and give NH4NO23, N2O, NO and NO2(based upon the concentration of HNO3)
    4Zn + 10HNO3 ⟶ 4Zn(NO3)2 + NH4NO3 + 3H2O
    Zn is on the top position of hydrogen in electrochemical series. So Zn displaces H2 from dilute H2SO4 and HCl with liberation of H2.
    Zn + H2SO4 ⟶ ZnSO4 + H2

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Redox Reactions
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