Class 12th

Which one of the following is correct for the adsorption of a gas at a given temperature on a solid surface?

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Vishal Baghel

Contributor-Level 10

During adsorption of a gas on solid surface, process is exothermic i.e. $Δ H = - v e (Δ H < 0)$ and entropy decreased, because gas particle resides on solid surface. Hence $Δ S < 0 .$

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11 months ago

83 g of ethylene glycol dissolved in 625 g of water. The freezing point of the solution is________K. (Nearest integer).

[Use: Molal Freezing point depression constant of water = 1.86 K kg mol^-1

Freezing point of water = 273K

Atomic masses: C : 12.0u, O : 16.0u, H : 1.0u]

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alok kumar singh

Contributor-Level 10

$Δ T_{f} = i * K_{f} * m$

{for ethylene glycol I = 1, due to non-ionisable}

$= 1 * 1.86 * \frac{83 * 1000}{62 * 625} K$

$= 3.984 K \approx 4 K$ (the nearest integer)

Hence, freezing point of solution = 273 K – 4K = 269 K.

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11 months ago

The major product formed in the following reaction is:

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Vishal Baghel

Contributor-Level 10

Kindly consider the following figure

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11 months ago

A college stores data on students, showing their gender and performance, on a computer disc. Due to virus, some of the data is lost and only the following could be recovered.

Study the table carefully and answer the questions given below it.

	Performance			Total
	Average	Good	Excellent	Total
Male			50
Female				96
Total		54

However, an expert committee arrived at the following conclusions

I. One-third of the male students were 'average'.

II. 40% of the students were female.

III. Half the total numbers of students were 'excellent'.

What fraction of total excellent students are female excellent students?

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Contributor-Level 10

Total number of excellent students = 120

Number of female excellent students = 70

Required fraction

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11 months ago

Given below are two statements:

Statement I: Sphalerite is a sulphide ore of zinc and copper glance is a sulphide ore of copper.

Statement II: It is possible to separate two sulphide ores by adjusting proportion of oil to water or by using 'depressants' in a froth flotation method.

Choose the most appropriate answer from the options given below:

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alok kumar singh

Contributor-Level 10

Sphalerite is the sulphide ore of zinc (ZnS) and copper glance Cu₂S is the sulphide ores of copper. Two sulphide ores can be separated by adjusting proportion of oil to water or by using depressant in froth flotation method.

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11 months ago

A college stores data on students, showing their gender and performance, on a computer disc. Due to virus, some of the data is lost and only the following could be recovered.

Study the table carefully and answer the questions given below it.

	Performance			Total
	Average	Good	Excellent	Total
Male			50
Female				96
Total		54

However, an expert committee arrived at the following conclusions

I. One-third of the male students were 'average'.

II. 40% of the students were female.

III. Half the total numbers of students were 'excellent'.

The ratio of female 'good' students to male 'average' students is

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Contributor-Level 10

Number of female good students = 8

Number of males average students = 48

Required ratio = 8 : 48 = 1 : 6

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11 months ago

Given below are two statements: one is labelled as Assertion (A) and the other is labelled as Reason (R).

Assertion (A): Photochemical smog causes cracking of rubber.

Reason (R): Presence of ozone, nitric oxide, acrolein, formaldehyde and peroxyacetyl nitrate in phtochemical smog makes it oxidizing.

Choose the most appropriate answer from the options given below:

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alok kumar singh

Contributor-Level 10

Photo-chemical smog is the mixture of various component like, O₃, NO, acrolein formaldehyde and peroxyacetyl nitrate and other oxidizing agents, which causes the cracking of rubber.

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11 months ago

The correct options for the products A and B of the following reactions are

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Vishal Baghel

Contributor-Level 10

CS₂ is non-polar, non-ionisable solvent and produce only para substituted compound due to the production of less Br⁺ ion, while H₂O itself a polar solvent and produce sufficient concentration of Br⁺ to attack on ortho and para position.

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11 months ago

A college stores data on students, showing their gender and performance, on a computer disc. Due to virus, some of the data is lost and only the following could be recovered.

Study the table carefully and answer the questions given below it.

	Performance			Total
	Average	Good	Excellent	Total
Male			50
Female				96
Total		54

However, an expert committee arrived at the following conclusions

I. One-third of the male students were 'average'.

II. 40% of the students were female.

III. Half the total numbers of students were 'excellent'.

The number of female 'good' students is

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Contributor-Level 10

From the above table, it is clear that number of female good students = 8

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New answer posted

11 months ago

Directions for questions: Answer the questions on the basis of the information given below.

A college stores data on students, showing their gender and performance, on a computer disc. Due to virus, some of the data is lost and only the following could be recovered.

Study the table carefully and answer the questions given below it.

	Performance			Total
	Average	Good	Excellent	Total
Male			50
Female				96
Total		54

However, an expert committee arrived at the following conclusions

I. One-third of the male students were 'average'.

II. 40% of the students were female.

III. Half the total numbers of students were 'excellent'.

The number of male 'good' students is

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