M1 = 17.45 M
M2 = 0.83 M
V2 = 250 ml
M1. V1= M2. V2
V1 = (M2. V2)/M1 = (0.83× 250)/ 17.45= 11.89 ml
3. Decreases
The concentration of hydrogen ions increasing creates an acid, which is 7 or below on the pH scale. If the pH value lessens from 7 to create an acid, that would mean it decreases.