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11 months ago

Class 12th Chemistry

Number of paramagnetic oxides among the following given oxides is_________.

Li₂O, CaO, Na₂O₂, KO₂, MgO and K₂O

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alok kumar singh

Contributor-Level 10

Given are the oxide of alkali and alkaline earth metals which are ionic in nature.

Simple oxide are Li₂O, CaO, MgO and K₂O.

Peroxide is Na₂O₂ and superoxide is KO₂.

All simple oxides are diamagnetic as it has no unpaired electron.

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11 months ago

Class 12th Chemical Kinetics

For the reaction A -> B, the rate constant K(in s^-1) is givne by

$l o g_{10} K = 20.35 - \frac{(2.47 * 1 0^{3})}{T} .$

The energy of activation in KJ mol^-1 is ______. (Nearest integer)

[Given : R = 8.314 J K^-1 mol^-1]

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Vishal Baghel

Contributor-Level 10

log k = 20.35 - $\frac{(2.47 * 1 0^{3})}{T}$

Comparing with,

$l o g k = l o g A - \frac{E a}{2.303 R T}$

$\frac{E a}{2.303 R} = 2.47 * 1 0^{3}$

= 47.29 kJ/mole

Ans. = 47

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11 months ago

Class 12th Chemistry

1.22 g of an organic acid is separately dissolved in 100 g of benzene (K_b = 2.6 K kg mol^-1) and 100 g of acetone (K_b = 1.7 K kg mol^-1). The acid is known to dimerize in benzene but remain as a monomer in acetone. The boiling point of the solution in acetone increases by 0.17°C. The increase in boiling point of solution in benzene in °C is x * 0^-2. The value of x is ________. (Nearest integer)

[Atomic mass : C = 12.0, H = 1.0, O = 16.0]

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Vishal Baghel

Contributor-Level 10

$Δ T_{b} = i K_{b} m$ $_{}_{}$

$m = \frac{w * 1000}{M * W_{s o l v e n t}}$

For acetone solution,

$0.17 = 1 * 1.7 * \frac{1.22 * 1000}{M * 100}$

For Benzene solution,

$2 A c i d \to {(A c i d)}_{2} ∴ i = 1 / 2$

$Δ T_{b} = i * K_{b} * m$

$= \frac{1}{2} * 2.6 * \frac{1.22 * 1000}{122 * 100} ° C$

= $0.13 ° C = 13 * 1 0^{- 2} ° C$ $^{}$

$∴ x * 1 0^{- 2} = 13 * 1 0^{- 2}$

$∴ x = 13$

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11 months ago

Class 12th Chemistry

The empirical formula for a compound with a cubic close packed arrangement of anions and with cations occupying all the octahedral sites is A_xB. The value of x is _______.

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Vishal Baghel

Contributor-Level 10

Effective number of atom in C.C.P

$∴ = \frac{1}{8} * 8 + \frac{1}{2} * 6$

= 4

Number of octahedral void = 4

Number of cations = 4

Number of anion = 4

Formula of compound = A₄B₄

Empirical formula = AB

Ans. x = 1

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11 months ago

Class 12th Physics

A carrier wave with amplitude of 250 V is amplitude modulated by a sinusoidal base band signal of amplitude 150V. The ratio of minimum amplitude to maximum amplitude for the amplitude modulated wave is 50 : x, then value of x is__________.

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alok kumar singh

Contributor-Level 10

$A_{m a x} = A_{c} + A_{m}$

$A_{m i n} = A_{c} - A_{m}$

$\frac{A_{m i n}}{A_{m a x}} = \frac{A_{c} - A_{m}}{A_{c} + A_{m}} = \frac{250 - 150}{250 + 150}$

$\Rightarrow \frac{100}{400} = \frac{50}{200}$

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11 months ago

Class 12th Maths

An electric instrument consists of two units. Each unit must function independently for the instrument to operate. The probability that the first unit functions is 0.9 and that of the second unit is 0.8. The instrument is switched on and it fails to operate. If the probability that only the first unit failed and second unit is functioning is p, then 98 p is equal to________.

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Raj Pandey

Contributor-Level 9

P (E₁)= 0.9 $P ({\bar{E}}_{t}) = 0.1 a n d P (E_{2}) = 0.8, P ({\bar{E}}_{2}) = 0.2$

$∴ R e q u i r e d p r o b a b i l i t y P = \frac{0.8 * 0.1}{0.8 * 0.1 + 0.2 * 0.1 + 0.9 * 0.2} = \frac{0.8}{2.8} = \frac{2}{7}$

$∴ 98 P = 28$

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11 months ago

Class 12th English

Answer the questions on the basis of the information given below.

In a school when a survey is conducted on liking of subjects out of three subjects physics, chemistry mathematics then outcome is as follow.

Total number of students who like physics, chemistry and mathematics is 30, 40, 50 respectively. 10 students shown interest in all three subjects, Number of students who like physics and mathematics both is equal to number of students who like chemistry and mathematics both and is equal to 3/4 times number of students who like physics and chemistry both 15 students like only chemistry.

When class teacher saw this survey report he to

...more

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alok kumar singh

Contributor-Level 10

From the given condition g = 10,

Number of students who like both Physics and Maths = 10 + f

Number of students who like both chemistry and Maths = 10 + e

From given condition 10 + f = 10 + e or e = f

Similarly from 3^rd condition ¾ (10 + e) = 10 + d

Or 30 + 3e = 40 + 4d

Since 15 students like only chemistry hence b = 15

Number of students who like only chemistry is 40

Hence e + g + d + b = 40

or e + 10 + (3e – 10)/4 + 15 = 40

or (7e – 10)/4 = 15 or 7e = 70 or e = 10

Hence a = 5, c = 20, f = e = 10, d = 5

Hence the distribution is as follows

As per the observation of class teacher actual numbers of students who like Physics in

...more

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11 months ago

Class 12th English

Parakrima band members are late for a concert in the evening. On their way, they come across a cracked bridge which has no lighting. The bridge is strong enough to hold at most two of them, and they have only one torch with them. Andy can get across the bridge in 2 minutes, Sandy takes 3 minutes, Kandy takes 6 minutes, but Mandy takes 9 minutes. Two band members together can move only as fast as the slower between the two, and one band member must be carrying the torch during the crossing. The band crosses the bridge in such a manner that the total time taken is minimum.

How many ways are there such that all can cross the bridge in min

...more

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Payal Gupta

Contributor-Level 10

Following are the possible ways in which Andy, Kandy, Mandy and Sandy can cross the bridge in minimum time.

Case I:

Journey	Men	Time
1 st trip	Andy, Sandy	3 min
Return	Andy, Sandy	2 min
2 nd trip	Kandy, Mandy	9 min
Return	Sandy	3 min
Final trip	Sandy, Andy	3 min
Total time		20 min

Case II:

Journey	Men	Time
1 st trip	Sandy	3 min
Return	Andy, Sandy	3 min
2 nd trip	Kandy, Mandy	9 min
Return	Andy	3 min
Final trip	Sandy, Andy	2 min
Total time		20 min

In total, there are 2 ways to do so.

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11 months ago

Class 12th Ncert Solutions Maths class 12th

A point z moves in the complex plane such that arg $(\frac{z - 2}{z + 2}) = \frac{π}{4},$ then the minimum value of ${| z - 9 \sqrt[]{2} - 2 i |}^{2}$ is equal to________.

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Raj Pandey

Contributor-Level 9

Let zc be the centre of the circle

$\frac{z_{c} - 2}{z_{c} + 2} = i \Rightarrow z_{c} = 2 i$

Radius of the circle = $\sqrt[]{4 + 4} = 2 \sqrt[]{2}$

Square off minimum distance AB = ${(7 \sqrt[]{2})}^{2} = 98$

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11 months ago

Class 12th English

Who are the last two persons to move across the bridge?

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Payal Gupta

Contributor-Level 10

Sandy and Andy are the last to cross the bridge.

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