Chemistry
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New answer posted
a year agoContributor-Level 10
This is a Long Answers Type Questions as classified in NCERT Exemplar
Ans: Catalytic reaction which depends on the pore structure of catalyst and size of the reactant, product molecules is known as shape-selective catalysis. Zeolites are considered as good shape-selective catalysts due to their honeycomb-like structures. They are aluminosilicates with three-dimensional network of silicates wherein some of the silicon atoms are replaced by aluminium atoms giving Al-O-Si frame work. The reactions taking place in zeolites depends upon size and shape of reactant and product molecules, the pores and cavities of the zeolites also. They are fo
New answer posted
a year agoContributor-Level 10
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.
New answer posted
a year agoContributor-Level 10
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.
New answer posted
a year agoContributor-Level 10
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.
New answer posted
a year agoContributor-Level 10
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.
New answer posted
a year agoContributor-Level 10
This is a Long Answers Type Questions as classified in NCERT Exemplar
Ans: In heterogeneous catalysis reactants are generally in gas phase and catalyst are in solid phase. The activity of a catalyst depends upon the strength of chemisorption to a large extent. The reactants must get adsorbed reasonably strongly on to the catalyst to become active. However, they must not get adsorbed so strongly that they are immobilized and other reactants are left with no space on the catalyst's surface for adsorption. It has been found that for hydrogenation reaction, the catalytic activity increases from Group 5 to Group 11 metals with maximum activi
New answer posted
a year agoContributor-Level 10
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).
New answer posted
a year agoContributor-Level 10
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)
New answer posted
a year agoContributor-Level 10
This is a short answer type question as classified in NCERT Exemplar
2F2 (g)+2H2O → 4H+ (aq)+4F- (aq)+O2 (g)
New answer posted
a year agoContributor-Level 10
This is a short answer type question as classified in NCERT Exemplar
In water hybridisation of oxygen is sp3. Angle should be109o (approx.) but due to LP - LP repulsion bond angle reduces to 104.5°.
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