NEET is one of the toughest exams for students looking to pursue their future in the medical field. By cracking this exam, students get a chance to study in the colleges at par with the ivy leagues. If appropriate and to the point study material is in hand, it becomes easier to study for this competitive exam. We at Aakash Institute provide the best study material for NEETexamswith an aim to give our students the best guidance for cracking the exam.
As you know, to crack NEET, the best scoring subject is Chemistry. Divided into three parts this subject can make or break the way into the entrance exam. At Aakash Institute, we provide an elaborate study material across subjects. And in this article, we will be covering the concept of pH in the most comprehensible and effective manner possible.
What is pH?
pH is the abbreviation for ‘Potential of Hydrogen’ and refers to the concentration of hydrogen ions in any liquid substance being measured. One can also say that pH is a unit for measuring the acidity and alkalinity of a liquid. If a substance is neither acidic nor basic, it is termed as neutral. The mathematical value of pH of the concentration of hydrogen ions is:
pH = -log10[H⁺]
Measurement of pH
Calculation of pH of any sample is done by measuring the potential of the solutionin reference to a standard hydrogen electrode. This method provides the value of zero for 1 molar solution of the H⁺ ions; this defines the minimum value of the pH scale. The cell potential for various values of H concentration can be derived by the Nernst Equation. For any solution at 25ºc the equation is:
Ecell = -0.0592log10[H⁺]
or
pH = Ecell/0.0592
But in general practice measurement of pH is not done in this manner as it requires a lot of standard parameters. It is measured with the help of a pH scale. The value on this scale ranges from 0.0 to 14.0. The values define the acidity and alkalinity of solutions like
- 0 is the value of concentrated hydrochloric acid (1M HCl)
- 7 is the value of water (neutral pH)
- 14 is the value of concentrated sodium hydroxide (1M NaOH)
{Note:-1 value of 10 M HCl is possible,but that is about the limit of acidity. Similarly, pH of 15 can be obtained for 10M of NaOH.}
By calculating the values of pH, we can describe the property of the solution if the value is:
- less than 7, the solution is acidic
- more than 7, the solution is basic
- 7 indicates the value of the neutral liquid
One can also calculate the molar concentration of the hydrogen ions if the pH of the solution is known, by this equation:
[H⁺] = 10-pH
The pH Meter
A pH meter is an instrument that translates the pH readings through the voltage difference between electrodes placed in the solution. It comprises of a voltmeter that is attached to a pH-responsive electrode and an unvarying electrode. When both electrodes are submerged in the solution, they replicate a battery. The glass electrode develops a charge directly associated with the activity of hydrogen-ion in the solution. The voltmeter measures the difference between both the electrodes to derive the value of pH of the solution.
The pOH Concept
Similar to the hydrogen-ion concentration, the hydroxide ion concentration can also be expressed logarithmically by pOH scale. The pOH of any solution is the negative logarithm of the concentration of hydroxide ions.
pOH = -log[OH–]
The relation between pH and pOH can be expressed by the equation
pH + pOH = 14
pH of various solutions
Solution | pH value | Acidic/Basic/Neutral |
Battery Acid | 0 | Acid |
Concentrated Sulphuric Acid | 1 | Acid |
Urine, Milk | 6 | Acid |
Pure Water | 7 | Neutral |
Sea Water, Eggs | 8 | Basic/Alkaline |
Ammonia Solution | 11 | Basic/Alkaline |
Bleach | 13 | Basic/Alkaline |
Chemistry holds utmost importance in increasing one’s score in the entrance exam. Students looking for a straightforward approach to understand the complications of the subject can contact us at Akash Institute. With the best study material for NEET exam and extremely dedicated faculty, we provide you with the perfect solution for clearing the upcoming NEET exam.
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