Question

9. State reason for the following statements: (2015)
i) Tap water conducts electricity where as distilled water does not.
ii) Dry Hydrogen chloride gas does not turn blue litmus red whereas dilute hydrochloric acid does.
iii) During summer season, a milk man usually adds a very small amount of baking soda to fresh milk.
iv) For a dilution of acid, acid is added into water and not water into acid.
v) Ammonia is a base but does not contain hydroxyl group.

please answer:)

Answer 1

1) this is because tap water contains some amount of impurities that distilled water doesn't contain and that's why it conducts electricity
2) an acid should be moist to change blue litmus to red because ionization takes place only in the presence of water by which h+ ions get activated.
3) because when we add water to acid it produces so much heat that the acid could splash out and may harm our face or body
4) this is because if water is added into the acid the reaction becomes highly exothermic and the acid will have the possibility of splashing onto ones face
5)Ammonia (NH3) is a weak base, which does not have hydroxyl group in its formula but it gives OH- ions when it reacts with water.

hope it helps!

Answer 2

I)Tap water contains dissolved salts in it. These salts dissociates into ions when electricity passed through it which are responsible for the electricity conductivity of tap water. But distilled water does not contain any dissolved salts, so it does not conduct electricity.

ii)HCl is acidic in aqueous as it dissociate into H+ and Cl- , in presence of water the Cl- ion get solvated and thus HCl show its acidic property but in gas phase the dissociation is not possible as nothing is there to stabilise the Cl- ion so no dissociation hence no acidic property.

iii)lactobacillus increases which converts into lactic acid decreasing the pH of milk During summers,temperature is high and hence The milkman adds baking soda to the milk to increase the pH of the solution as it is a base and neutralises the milk in summers.

iv)The mixing of water to an acid is highly exothermic in nature.
If water is added to an acid it produces very large amount of heat which can brake the container in which diluting the acid and some times even causes burnings.
So, it is adivised to add concentrated acid to water very slow manner.

v)Ammonia when dissolved in water it forms ammonium hydroxide.

Ammonium hydroxide redily ionizes to form ammonium ions (NH4+) and hydroxide ions(OH-). Thus the solution ammonia is considered as a base.

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