Question

According to Bronsted concept, water is a/an:
A) Base
B) Acid
C) Both acid and base
D) Salt

Answer 1

Hint: We have to know that in generally, pH value of all acids are in between \[{\text{0}}{\text{.9}}\]-\[6.9\] and all the bases are in between \[7.1 - 14.0\]. But, Arrhenius theory has some limitations. One of the main limitations is not being able to explain the behaviour of acids and bases in non-aqueous solvents such as acetone etc,. It is not able to explain the acid which doesn't contain hydrogen and bases don’t contain hydroxyl ion in the formula. Ammonia is a well known base that is not accepted as base in Arrhenius base. These limitations are recovered by further coming theories like the Bronsted and Lowry concept of acids and bases.

Complete answer:
We have to know that according to the Bronsted concept, acid is nothing but the substance able to donate protons to other substances.
According to the Bronsted concept, base is nothing but the substance able to accept protons from other substances.
According to the Bronsted concept, water acts both acid and base because it is able to donate protons to other substances and also able to accept protons from other substances.
According to the above discussion, we conclude water is both acid and base.

Hence, the option C is the correct answer.

Note:
We need to know that Arrhenius is one of the concepts for acid and bases. Swedish chemist Arrhenius is the world's first chemist to talk about acid and bases. Depending on his concept and limitations later so many concepts are developed. Even Arrhenius is the birthplace of the concept of acids and bases. Followed by Arrhenius the concept of acids and bases discuss Bronsted and Lowry in the world.
According to the Arrhenius concept, one substance said to be acid means acid is nothing but a substance that dissociates to give hydrogen ion when decomposed in the water.
Examples of Arrhenius acids are hydrochloric acid (\[HCl\]), sulphuric acid (\[{H_2}S{O_4}\]), nitric acid (\[HN{O_3}\]) etc,.
According to Arrhenius' concept one substance said to base means bases is nothing but a substance that dissociates to give hydroxyl ion when decomposed in water.
Examples of Arrhenius bases are sodium hydroxide (\[NaOH\]), calcium hydroxide (\[Ca{(OH)_2}\]) etc,.