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5 months ago

Class 12th Inverse Trigonometric Functions

For $k \in R,$ let the solutions of the equation $c o s (s i n^{- 1} (x c o t (t a n^{- 1} (c o s (s i n^{- 1} x)))))$ =, 0 < $| x | < \frac{1}{\sqrt[]{2}}$ be and , where the inverse trigonometric functions take only principal values. If the solutions of the equation x2 – bx – 5 = 0 are $\frac{1}{α^{2}} + \frac{1}{β^{2}} a n d \frac{α}{β} t h e n \frac{b}{k^{2}}$ is equal to

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Payal Gupta

Contributor-Level 10

use $s i n^{- 1} x = c o s^{- 1} \sqrt[]{1 - x^{2}}$

$t a n^{- 1} \sqrt[]{1 - x^{2}} = c o t^{- 1} \frac{1}{\sqrt[]{1 - x^{2}}}$

$s i n^{- 1} \frac{x}{\sqrt[]{1 - x^{2}}} = c o s^{- 1} \frac{\sqrt[]{1 - 2 x^{2}}}{\sqrt[]{1 - x^{2}}}$

Sum of roots b = 1 + 2 $\frac{(k^{2} - 1)}{k^{2} - 2}$

Product of roots 5 = 2 $(\frac{k^{2} - 1}{k^{2} - 2})$

b = 4, k² = $\frac{1}{3}$

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Class 12th Chemistry

In the following reaction

The % yield for reaction I is 60% and that of reaction II is 50%. The overall yield of the complete reaction is___________% [Nearest integer]

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Payal Gupta

Contributor-Level 10

Let initial moles of reactant taken = n. Total moles obtained for benzene sulphonic acid = 0.6 n (with % yield = 60%)

Moles of benzene sulphonic acid before reaction II = 0.6n

Moles obtained for phenol (with % yield 50%) = 0.6 * 0.5 n = 0.3 n

So, overall % age yield of complete reaction = $\frac{0.3 n}{n} * 100 = 30 %$

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Class 12th Chemistry

Optical activity of an enantiomeric mixture is + 12.6° and the specific rotation of (+) isomer is +30°. The optical purity is_____________%

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Payal Gupta

Contributor-Level 10

$% O p t i c a l p u r i t y = \frac{O b s e r v e d r o t a t i o n o f m i x t u r e * 100}{r o t a t i o n o f p u r e e n a u t i o m e r}$

$= \frac{+ 12.6}{+ 30} * 100 = 42 %$

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Class 12th Chemistry

In the titration of KMnO₄ and oxalic acid in acidic medium, the change in oxidation number of carbon at the end point is____________.

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Payal Gupta

Contributor-Level 10

$2 K M n O_{4} + 5 H_{2} {\overset{+ 3}{C}}_{2} O_{4} + 3 H_{2} S O_{4} (d i l) \to K_{2} S O_{4} + 2 M n S O_{4} + 10 C {\overset{+ 4}{O}}_{2} + 8 H_{2} O$

Oxidation state of carbon changes from +3 to +4

$∴$ change in O. S is 1

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Class 12th Chemistry Coordination Compounds

The conductivity of a solution of complex with formula CoCl₃(NH₃)₄ corresponds to 1 : 1 electrolyte, then the primary valency of central metal ion is__________________.

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Payal Gupta

Contributor-Level 10

Complex is $[C o {(N H_{3})}_{4} C l_{2}] C l$

Primary valency = No. of ionisable species = 1

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Class 12th Chemistry

At 310 K, the solubility of CaF₂ in water is 2.34 * 10^-3 g/ 100 mL. The solubility product of CaF₂ is ____________* 10^-8 (mol/L)³. (Give molar mass : CaF₂ = 78 gmol^-1)

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Payal Gupta

Contributor-Level 10

Solubility of CaF₂ = S mol/L

$S = \frac{2.34 * 1 0^{- 3}}{0.1 * 78} = \frac{2.34}{78} * 1 0^{- 2} = 3 * 1 0^{- 4} m o l / L$

$K_{s p} (C a F_{2}) = 4 S^{3} = 4 {(3 * 1 0^{- 4})}^{3} = 108 * 1 0^{- 12}$

= 0.0108 * 10^-8 (mol/L)³

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Class 12th Chemistry Chemical Kinetics

2NO + 2H₂ → N₂ + 2H₂O

The above reaction has been studied at 800°C. The related data are given in the table below.

Reaction serial number	Initial Pressure of H₂ / kPa	Initial Pressure of NO / kPa	Initial rate (-dP/dT)/(kPa/s)
1	65.6	40.0	0.135
2	65.6	20.1	0.033
3.	38.6	65.6	0.214
4.	19.2	65.6	0.106

The order to the reaction with respect to NO is_______________.

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Payal Gupta

Contributor-Level 10

On decreasing pressure of NO by a factor of '2' the rate of reaction decreases by a factor of '4'

$∴$ Order of reaction w.r.t 'NO' = 2

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Class 12th Chemistry

20 mL of 0.02 M K₂Cr₂O₇ solution is used for the titraction of 10 mL of Fe²⁺ solution in the acidic medium. The molarity of Fe²⁺ solution is ___________* 10^-2 M. (Nearest Integer)

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Payal Gupta

Contributor-Level 10

Meq of K₂Cr₂O₇ = Meq of Fe²⁺

(Molarity * Volume * nf) of K₂Cr₂O₇ = (molarity * volume * nf) of Fe²⁺

0.02 * 20 * 6 = M * 10 * 1

M = 0.24 M

Molarity = 24 * 10^-² M

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Class 12th Physics

A long cylindrical volume contains a uniformly distributed charge of density $ρ C m^{- 3} .$ The electric field inside the cylindrical volume at a distance $x = \frac{2 ε_{0}}{ρ} m$ from its axis is_________Vm^-1.

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Payal Gupta

Contributor-Level 10

$x = \frac{2 ε_{0}}{ρ}$

$E 2 π x l = \frac{ρ π x^{2} l}{ε_{0}}$

$E_{x} = \frac{ρ x^{2}}{2 x ε_{0}} = \frac{ρ x}{2 ε_{0}}$

$= \frac{ρ}{2 ε_{0}} * \frac{2 ε_{0}}{ρ} = 1 v / m$

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Class 12th Physics

A 1 m long copper wire carries a current of 1 A. If the cross section of the wire is 2.0mm² and the resistivity of copper is 1.7 * 10^-8 $Ω m,$ the force experienced by moving electron in the wire is _______* 10^-23N.

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Payal Gupta

Contributor-Level 10

i = 1 A $j = σ E$

A = 2mm²

$ρ = 1.7 * 1 0^{- 8} Ω m$ $F = e E = \frac{e j}{σ} = \frac{e i}{A σ} = \frac{e i ρ}{A}$

= $\frac{1.6 * 1 0^{- 19} * 1.7 * 1 0^{- 8}}{2 * 1 0^{- 6}}$

= 136 * 10^-23 N

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