Chemistry

This is a Long Answers Type Questions as classified in NCERT Exemplar

Ans: This method is used for removing gangue from sulphide ores. In this, a suspension of powdered ore is made with water. To which both the collectors and froth stabilisers are added. Collectors for example pine oils, fatty acids, xanthates enhance non-wettability of the mineral particles and froth stabilisers such as cresols, aniline stabilise the froth.

This is a multiple choice answer as classified in NCERT Exemplar

Option (ii)

LiH < NaH < KH < RbH < CsH

In ionic hydride as it is formed by the s-Block element, down the group, electropositive character increases.

This is a Long Answers Type Questions as classified in NCERT Exemplar

Ans:  (i) Separation of inert gases: Due to a difference in the degree of adsorption of gases by charcoal, a mixture of noble gases can be separated by adsorption on coconut, a charcoal at different temperatures.

(ii) Adsorption indicators: Surfaces of certain precipitates such as silver halides have the property of adsorbing some dyes like eosin, fluorescein, and so produce a characteristic colour at end point.

(iii) Chromatographic analysis: It is based on the phenomenon of adsorption and has a number of applications in analytical and industrial fields.

This is a multiple choice answer as classified in NCERT Exemplar

option (iv)

Loss of an electron from a hydrogen atom results in a nucleus of very small size as compared to other atoms or ions. Due to its small size it cannot exist free.

Loss of the electron from hydrogen atom results in nucleus size (H⁺) of 1.5 * 10^-3. This is extremely small as compared to normal atomic and ionic sizes of 50 to 200 pm. As a consequence, H⁺ does not exist freely and is always associated with other atoms or molecules.

This is a multiple choice answer as classified in NCERT Exemplar

option (ii)

Its tendency to gain a single electron in its valence shell to attain stable electronic configuration.

Like halogens (with ns²np⁵ configuration belonging to the seventeenth group of the periodic table), it is short by one electron to the corresponding noble gas configuration, helium (ls²).

This is a short answer type question as classified in NCERT Exemplar

H₂O (l)+NH₃ (aq) → OH^- (aq)+NH₄⁺ (aq)

H₂O (l)+H₂S (aq) → H₃O⁺ (aq)+HS^- (aq)

This is a short answer type question as classified in NCERT Exemplar

2F₂ (g)+2H₂O → 4H⁺ (aq)+4F^- (aq)+O₂ (g)

This is a short answer type question as classified in NCERT Exemplar

In water hybridisation of oxygen is sp³. Angle should be109^o (approx.) but due to LP - LP repulsion bond angle reduces to 104.5°.

This is a short answer type question as classified in NCERT Exemplar

Because H₂SO₄ can activate the decomposition of H₂O₂.