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Class 12th Chemistry

The most common oxidation state of Lanthanoid elements is +3. Which of the following is likely to deviate easily from +3 oxidation state?

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Payal Gupta

Contributor-Level 10

$C e^{3 +} \to [X e] 4 f^{1} 5 d^{0}$

$C e^{4 +} \to [X e] 4 f^{0} 5 d^{0}$ (Noble gas configuration)

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Class 12th Chemistry

SO₂Cl₂ on reaction with excess of water results into acidic mixture

SO₂Cl₂ + H₂O -> H₂SO₄ + 2HCl

16 moles of NaOH is required for the complete neutralization of the resultant acidic mixture. The number of moles of SO₂Cl₂ used is:

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alok kumar singh

Contributor-Level 10

Let a moles of SO₂Cl₂ is taken

Then no. of moles of H₂SO₄ = a moles

No. of moles of HCl = 2a moles

No. of moles of NaOH required = 2a + 2a = 4a = 16

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Class 12th Chemistry

The role depressants in 'Froth Floatation method' is to

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Payal Gupta

Contributor-Level 10

In sulphide ore, depressants selectively prevent impurity from coming to the fourth.

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Class 12th Physics Moving Charges and Magnetism

Metallic disc of inner radius and outer radius $2 R$ is rotating with an angular speed w . What will be the electric potential difference that appears between the inner and outer periphery. The mass of electrons is $m$ and charge is $e$ .

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Vishal Baghel

Contributor-Level 10

Answer (1)

$e E = e \frac{d V}{d r} = m ω^{2} r$

$? V = \int d V = \int_{R}^{2 R} \frac{m}{e} ω^{2} r d r$

$= ? V = \frac{3 m ω^{2} R^{2}}{2 e}$

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Class 12th Chemistry Coordination Compounds

Total number of relatively more stable isomer(s) possible for octahedral complex $[C u {(e n)}_{2} {(S C N)}_{2}]$ will be________________.

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alok kumar singh

Contributor-Level 10

$[C u {(e n)}_{2} {(S C N)}_{2}]$

More stable isomers = 3 (trans isomers)

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Class 12th Chemistry

Match List I with List II

List I Enzyme	List II Conversion of
A. Invertase	I. Starch into maltose
B. Zymase	II. Maltose into glucose
C. Diastase	III. Glucose into ethanol
D. Maltase	IV. Cane sugar into glucose

Choose the most appropriate answer from the options given below

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Payal Gupta

Contributor-Level 10

Invertase → Cane sugar to glucose and fructose

Zymase → Glucose to ethanol

Diastase → Starch to Maltose

Maltase → Maltose to glucose

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Class 12th Physics

In the circuit shown below, maximum zener diode current will be _________mA.

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Payal Gupta

Contributor-Level 10

$l = \frac{120 - 60}{4000} = 0.015 A$

Thus l₂ = l - L_L

= 0.015 – 0.006

= 0.009 = 9mA

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Class 12th Physics Atoms

In the hydrogen spectrum, $λ$ be the wavelength of first transition line of Lyman series. The wavelength difference will be $" a λ "$ between the wavelength of 3^rd transition line of Paschen series and that 2^ndtransition line B Balmer series where a = __________.

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Payal Gupta

Contributor-Level 10

For first line of Lyman

$\frac{1}{λ} = R (1 - \frac{1}{4}) = R \frac{3}{4}$

$λ = \frac{4}{3 R}$

3rd line (Paschen)

$\frac{1}{λ_{3}} = R (\frac{1}{3^{2}} - \frac{1}{6^{2}}) = \frac{R}{9} * \frac{3}{4}$

2nd line (B almer)

${\frac{1}{λ}}_{2} = R (\frac{1}{2^{2}} - \frac{1}{4^{2}}) = \frac{R}{4} * \frac{3}{4}$

$a (\frac{4}{3 R}) = \frac{20}{3 R} \Rightarrow a = 5$

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Class 12th Physics Ray Optics and Optical Instruments

The graph between $\frac{1}{u} a n d \frac{1}{v}$ for a thin convex lens in order to determine its focal length is plotted as shown in the figure. The refractive index of lens is 1.5 and its both the surfaces have same radius of curvature R. The value of R will be _________cm. (where u = object distance, v = image distance)