Which of the following is a base–conjugate acid pair?
h2o and h3o+
h2o and h2po4–
h2po4– and hpo42–
h2po4– and h3o+

Answer : The correct options is,

Explanation :

According to the Bronsted Lowry conjugate acid-base pair concept, an acid is a substance which donates protons and a base is a substance which accepts protons.

From the given options, and represents a base-conjugate acid pair.

The balanced reaction will be :

In this, is a base which accepts a proton to form conjugate acid .

Hence, the correct options is,

the best answer is d because the strong cohesion is caused by the ability of water molecules to undergo hydrogen bonding.

a is incorrect because when water solidifies, it becomes   ice, which expands and occupies a bigger volume for the same mass of water in its liquid state.

b is incorrect because water has high surface tension. besides bonding to itself it hydrogen bonds to other molecules at the top decreasing possibility for breaking of attractive forces.

c is incorrect because the water molecule has oxygen which is highly electronegative and so pulls the electron pair towards itself creating a dipole moment, making the molecule polar.

e is incorrect because water has strong adhesion, ability to stick to other molecules such as glass because of this molecules having stronger hydrogen bonding than water.