Question

(a) What is produced if an acid is added to a base?
(b) Why does dry HCl gas not change the colour of dry litmus paper?
(c) What colour does phenolphthalein indicator turn when added to an alkali (such as sodium hydroxide)?

Answer 1

Answer:

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Here's your answer.......

a) When an acid is added to a base, then the following bi-products are "salt" and "water"..

b) Dry HCl gas does not change the colour of dry litmus paper as because it does not have any H+ ions. or may be there may be a red litmus paper... so it won't react with HCl..

c) As we know that phenolphthalein is a weak acid.... When any alkali ( sodium hydroxide) is added to it, then it changes its colour into pink.....

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Answer 2

The Phenolphthalein Indicator Turns Pink

Explanation:

(a) When an acid is added to a base, the acid nullifies the effect of the base, and conversely, the effect of an acid is nullified by a base to give a salt and water. Such a type of reaction between an acid and a base to give a salt and water is known as a neutralization reaction.

The reaction is shown as-

Acid + Base → Salt + Water

 For example, when sodium hydroxide is treated with hydrochloric acid, the reaction can be written as follows.

$NaOH(aq) + HCl(aq) --> NaCl(aq) + H_2O(l)$  

(b) Dry HCl gas does not undergo dissociation to form ions, because of the absence of an aqueous medium, whereas the color of litmus paper changes only in the presence of ions.  

So,  

The color of the dry Litmus paper does not changes owing to dry HCl

 

(c) A phenolphthalein indicator turns pink when added to an alkali (such as sodium hydroxide).