Select the statements that correctly describe buffers. A) A buffer is made up of a strong acid and a strong base.
B) The pH of a buffer solution does not change significantly when a small amount of acid is added.
C) The pH of a buffer solution is determined by the ratio of the concentration of acid to the concentration of base.
D) The K_a of a buffer decreases slightly when a small amount of acid is added to the buffer solution.
E) A strong acid added to the buffer solution reacts with the weak acid of the buffer.

B) The pH of a buffer solution does not change significantly when a small amount of acid is added.

C) The pH of a buffer solution is determined by the ratio of the concentration of acid to the concentration of base.

Explanation:

Buffer solution is useful in maintaining the pH of a solution constant . It is made of a weak acid and its salt or a weak base and  its salt . Ph of a buffer is given by the following relation .

pH = pKa + log [ A⁻ ] / [ HA ]

A- is a base and HA is a weak acid .

When we add acid , it reacts with A⁻ or base and gets neutralised .

When we add base , it reacts with acid HA and gets neutralised . In this way it maintains the pH of the solution .

we can conclude that the melting point of table salt is above room temperature (it's actually 801 deg c). the melting point of mercury must be below room temperature (- 39 deg c).