An aqueous solution at 25 c has a OH- concentration of . Calculate the concentration. Be sure your answer has the correct number of significant digits.

Full Question:

An aqueous solution at 25 C has a OH- concentration of 2.5x10-4M . Calculate the H3O+ concentration. Be sure your answer has the correct number of significant digits.

4×10−9M

Explanation:

From the question;

[OH−] = 2.5x10-4M

[H3O+] = ?

The relationship between both parameters is given as;

Kw = [H3O+] * [OH−]

where k self-ionization constant of water, Kw = 1×10−14, which has no units.

Upon solving for [H3O+];

[H3O+] = Kw / [OH−]

Kw = 1×10−14

[H3O+]  = (1×10−14 ) / 2.5x10-4

[H3O+]  = 0.4 * 10-10

[H3O+]   = 4×10−9M

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%