Which statement is true? (more than one may be selected) a) Substances that release protons when they dissolve in water are termed bases and result in a pH higher than 7. b) Substances that release protons when they dissolve in water are termed acids and result in a pH higher than 7. c) Bases (alkali) are any aqueous environments where the proton content decreases and the pH increases. d) Acids are any aqueous environments where the proton content increases and the pH decreases. e) Substances that release protons when they dissolve in water are termed acids and result in a pH lower than 7. Solution Ans. Which statement is true? (more than one may be selected) a) Substances that release protons when they dissolve in water are termed bases and result in a pH higher than 7. Incorrect- it is an acid b) Substances that release protons when they dissolve in water are termed acids and result in a pH higher than 7. Incorrect- it is “pH lower than 7” c) Bases (alkali) are any aqueous environments where the proton content decreases and the pH increases. d) Acids are any aqueous environments where the proton content increases and the pH decreases. e) Substances that release protons when they dissolve in water are termed acids and result in a pH lower than 7. Correct option Correct option: E Explanation: Acid is a molecule or ion that donates proton. An aqueous environment may facilitate acceptance or release of proton to/from a molecule, but the environment can’t be termed an acid or base because it does not represent a specific molecule or ion. For example, adding HCl to NaCl solution (say, normal saline) cause donation of proton from HCl molecule to the solution. Here, NaCl- the aqueous environment, accept a proton- BUT NaCl solution is NOT a base because it does NOT represent a specific molecule or ion. So, for being an acid or base- it must be a molecule or ion, NOT an aqueous environment. Though H2O (water) alone can act as acid or base depending on the acid/base added to it; but the term ‘aqueous environment’ is NOT exclusive for water. So, it can’t be treated as an acid or base. Therefore, options C, D are incorrect. pH = - log [H]. Addition of an acid to water (solvent) cause an increase in [H+] ions in water because acid donates proton to water. Increase in [H+] lowers the pH , i.e. pH is reduced below 7.0; say pH lowered from 7.0 to 4.0. Thus “Substances that release protons when they dissolve in water are termed acids and result in a pH lower than 7.” So, options A, B are incorrect..

1. Which statement is true? (more than one may be selected)
a) Substances that release protons when they dissolve in water are termed bases and result in a
pH higher than 7.
b) Substances that release protons when they dissolve in water are termed acids and result in a
pH higher than 7.
c) Bases (alkali) are any aqueous environments where the proton content decreases and the pH
increases.
d) Acids are any aqueous environments where the proton content increases and the pH decreases.
e) Substances that release protons when they dissolve in water are termed acids and result in a
pH lower than 7.
Solution
Ans. Which statement is true? (more than one may be selected)
a) Substances that release protons when they dissolve in water are termed bases and result in a
pH higher than 7. Incorrect- it is an acid
b) Substances that release protons when they dissolve in water are termed acids and result in a
pH higher than 7. Incorrect- it is “pH lower than 7”
c) Bases (alkali) are any aqueous environments where the proton content decreases and the pH
increases.
d) Acids are any aqueous environments where the proton content increases and the pH decreases.
e) Substances that release protons when they dissolve in water are termed acids and result in a
pH lower than 7. Correct option
Correct option: E
Explanation: Acid is a molecule or ion that donates proton.
An aqueous environment may facilitate acceptance or release of proton to/from a molecule, but
the environment can’t be termed an acid or base because it does not represent a specific molecule
or ion. For example, adding HCl to NaCl solution (say, normal saline) cause donation of proton
from HCl molecule to the solution. Here, NaCl- the aqueous environment, accept a proton- BUT
NaCl solution is NOT a base because it does NOT represent a specific molecule or ion. So, for
being an acid or base- it must be a molecule or ion, NOT an aqueous environment. Though H2O
(water) alone can act as acid or base depending on the acid/base added to it; but the term
‘aqueous environment’ is NOT exclusive for water. So, it can’t be treated as an acid or base.
Therefore, options C, D are incorrect.
pH = - log [H]. Addition of an acid to water (solvent) cause an increase in [H+] ions in water

2. because acid donates proton to water. Increase in [H+] lowers the pH , i.e. pH is reduced below
7.0; say pH lowered from 7.0 to 4.0. Thus “Substances that release protons when they dissolve in
water are termed acids and result in a pH lower than 7.”
So, options A, B are incorrect.