Class 12th

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$K = A . e^{- E a / R T} = (6.5 * 1 0^{2}) e^{- 26000 K / T}$

$\frac{E a}{8.314} = 26000$

E_a = 216.164kJ/mol $≅$ 216

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Which one of the following techniques is not used to spot components of a mixture separated in thin layer chromatographic plate?

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Contributor-Level 9

In thin layer chromatography, the spots of colourless compounds, which are invisible to eyes can be detected by putting the plate under UV light.

Another detection technique is to place the plate in a covered jar containing I₂ (s). Sometimes an appropriate reagent may also be sprayed on the plate, ninhydrin in case of amino acids.

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The cell potential for the given cell at 298 K

$P t | H_{2} (g, 1 b a r) | H^{+} (a q) | | C u^{2 +} (a q) | C u (s) i s 0.31 V .$ The pH of the acidic solution is found to be 3, whereas the concentration of Cu²⁺ is 10^-x M. The value of x is________.

(Given : $E_{C u^{2 +} / C u}^{Θ} = 0.34 V a n d \frac{2.303 R T}{F} = 0.06 V)$

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Contributor-Level 10

H₂ (g) + Cu²⁺ (aq) $\overset{}{\to}$ 2H⁺ (aq) + Cu (s)

$∴ E_{c e l l} = E_{c e l l}^{0} - \frac{2.303 R T}{n f} l o g Q$

0.31 = 0.34 - $\frac{0.06}{2} l o g \frac{[H^{+}]}{C u^{2 +}}$

$[C u^{2 +}] = 1 0^{- 7} (? [H^{+}] = 1 0^{- 3})$

x = 7

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3 months ago

Which amongst the following is not a pesticide?

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Class 12th Chemistry Coordination Compounds

Contributor-Level 9

DDT, organophosphates and dieldrin are pesticides.

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Given below are two statements:

Statement I : ${[N i {(C N)}_{4}]}^{2 -}$ is square planar and diamagnetic complex, with dsp² hybridizatin for Ni but $[N i {(C O)}_{4}]$ is tetrahedral, paramagnetic and with sp³ hybridization for Ni.

Statement II : ${[N i C l_{4}]}^{2 -} a n d [N i {(C O)}_{4}]$ both have same d-electron configuration have same geometry and are paramagnetic.

In light the above statements, choose the correct answer from the options given below:

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Contributor-Level 9

${[N i {(C N)}_{4}]}^{2 -}$

CN^- is strong field ligand

$N i^{2 +} = 4 s^{0} 3 d^{8}$

Here; ${[N i {(C N)}_{4}]}^{2 -}$ is square planar and diamagnetic.

$[N i {(C O)}_{4}]$

Ni = 4s²3d⁸ Co is strong field ligand.

Here ; $[N i {(C O)}_{4}]$ is tetrahedral and diamagnetic

${[N i {(C N)}_{4}]}^{2 -}$ has 3d⁸ configuration while $[N i {(C O)}_{4}]$ has 3d¹⁰ configuration.

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Class 12th Solutions

Elevation in boiling point for 1.5 molal solution of glucose in water is 4 K. The depression in freezing point for 4.5 molal solution of glucose in water is 4K. The ratio of molal elevation constant to molal depression constant (K_b/K_f) is________.

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Contributor-Level 10

$Δ T_{b} = i K_{b} m$

$Δ T_{f} = i K_{f} m$

$∴ \frac{4}{4} = \frac{K_{b} * 1.5}{K_{f} * 4.5}$

$\frac{K_{b}}{K_{f}} = 3$

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3 months ago

Which one of the lanthanoids given below is the most stable in divalent form?

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Contributor-Level 9

Valence shell electronic configuration of Eu in +2 O.S is,

$E u^{2 +} = 6 s^{0} 4 f^{7}$

It has half filled f-sub shell and stable.

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3 months ago

The mixture of chloroxylenol and terpineol is an example of

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Contributor-Level 10

Antiseptic Dettol is mixture of chloroxylenol and terpineol

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Given are two statements one is labeled as Assertion A and other is labeled as Reason R.

Assertion A : Magnesium can reduce Al₂O₃ at a temperature below 1350°C, while above 1350°C aluminium can reduce MgO

Reason R : The melting and boiling points of magnesium are lower thatn those of aluminium.

In light of the above statements, choose most appropriate answer for the options given below:

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Contributor-Level 9

Below 1350° C, Mg can reduce Al₂O₃ and above 1350°C, Al can reduce MgO (from Ellingham diagram).

Melting and boiling point of Mg are lower than that of Al.

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3 months ago

The structure of protein that is unaffected by heating is

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