All solutions contain a certain pH value that depends on the nature of both solute and solvent. A pH value tells the nature of a substance whether it is acidic, alkaline, or neutral. An acid is a species that donates a proton in a solution while a base is a specie that dissociates OH ions in the solution.
The pH value of a substance can be calculated using our online pH calculator. A pH value tells the extent of acidity and basicity of a substance. You would learn the calculation of pH value in this article.
Determination of pH value
Different apparatuses are used in the lab to check the pH of a substance. The conventional method is to use litmus paper. Litmus paper gives different colors when dipped in acidic and basic media. Then the color of the litmus paper is matched with the pH scale and checked the exact value of pH between 0 to 14 on a pH scale.
7 indicated neutral nature, a value below 7 indicates acidic nature, and a value above 7 indicates basic nature. Water is a neutral molecule and its pH is 7. The modern apparatus to determine the pH value is a pH meter.
It contains a column that is dipped in the solution and the digital value of pH appears on the screen. Here, we don’t need a pH scale. These were the methods of determining the pH value in the laboratory but suppose you are in an examination hall where you don’t have any of these apparatus. Then how to calculate the pH value? Here you would use a simple formula to calculate the pH value manually.
The pH Calculator
The theoretical calculation of pH is a complex process so we recommend you use a pH calculator for a quick answer. Enter the concentration of hydrogen or hydroxyl ions released in the solution or the simple molarity of the solution and press the “calculate” button. You will the pH value of your desired solution. Also, you can enter the name of the substance like HCl in the case of hydrochloric acid solution.
Calculation of pH value
Theoretically, the pH value for acids is calculated by using the molarity of the solution and the number of free H+ ions released in the solution. In the case of acids, first, calculate the pOH value and then subtract it from 14 to get the pH value (because base releases OH ion). Following is the formula to calculate the pH of the given solution.
pH = -log [H+]
pOH = -log [OH-1]
Concentration of free H+ ions = Molarity x no. of free H+ ions
Let us calculate the pH value of 0.05M H2SO4 solution
H2SO4 2H+ + SO4-
Concentration of free H+ ions = 0.05 x 2
Concentration of free H+ ions = 0.1
pH of H2SO4 = -log [OH-1]
pH of H2SO4 = -log [0.1]
pH of H2SO4 = 1
Answer; The pH of 0.05M sulphuric acid is 1 which means it is a very strong acid and you need to handle it with great care (Lower the pH value, stronger the acid).