Aph 4 buffer solution is prepared by dissolving one mole of a weak acid ha (pka = 4.0) and one mole naa in 1 l of water. when the volume is increased to 10 l by adding distilled water, the ph of the resulting solution is closest to:

pH is closest to 4.0

Explanation:

According to Henderson-Hasselbalch equation for a buffer consist of an weak acid (HA) and it's conjugate base ()-

where and [HA] represents concentration (in molarity) of and HA respectively.

We know,

Number of moles of HA and remains same even after diluting the solution to 10 L.

So,

So,

Hence pH is closest to 4.0

1. for the first question, we must find the mass of the anhydrous salt, mgso₄. the molar mass for mgso₄·7h₂o is 246.47 g/mol, while that of mgso₄ is 120.37 g/mol.7.834 g mgso₄·7h₂o * 1 mol mgso₄·7h₂o/246.47 g * 1 mol mgso₄/1 mol mgso₄·7h₂o * 20.37 g mgso₄/mol = 0.647 g mgso₄

2. mass of water = mass of sample - mass of anhydrous salemass of water = 7.834 - 0.647 = 7.19 gpercent water in hydrate = 7.19/7.834 * 100 = 91.74%