Question

What is the pH of a $ 0.005 $ (M) $ {H_2}S{O_4} $ solutions?
(A) 3
(B) 4
(C) 2
(D) 5

Answer 1

Hint: The concentration of any compound can be written by molarity. pH helps to calculate the hydrogen ion concentration in a solution. It can be calculated by the given formula. We have to find the moles of hydrogen ion released by 1 mole of sulphuric acid and substitute the value.
Formula Used: $ pH = - \log \left[ {{H^ + }} \right] $

Complete step by step solution:
Molarity is also known as the molar concentration or the substance concentration or the amount concentration. It is the measure of concentration of a chemical species in a particular solute or solution. The most commonly used unit for molarity is moles per litre. Molarity is equal to the number of moles of the solute divided by the volume of solution in litres. Molarity is a volume dependent quantity. Hence, as the temperature changes, volume changes and molarity also changes.
pH denotes the potential of hydrogen or the power of hydrogen. It is used to specify acidity or basicity of an aqueous solution. Acidic solutions have lower pH values and basic solutions have higher pH values. pH is the negative of the base 10 logarithm of hydrogen ion concentration. At $ {25^ \circ } $ C, solutions are acidic when pH is less than seven, basic when pH is greater than 7 and neutral when pH is 7.
The formula for pH is as follows,
 $ pH = - \log \left[ {{H^ + }} \right] $
Sulphuric acid is a diprotic acid. Hence, the concentration of hydrogen ions is double the concentration of sulphuric acid. The concentration of hydrogen ions is $ 0.01 $ M.
The pH of sulphuric acid is given as follows,
 $ \left[ {{H^ + }} \right] = 2 \times 0.005{\rm{ M = 0}}{\rm{.01 M}} $
 $ \therefore pH = - \log \left[ {0.01} \right] = 2 $
Therefore, the pH of sulphuric acid is 2.
Hence the correct answer is option C.

Note:
The other name of sulphuric acid is the oil of vitriol. It is composed of the elements sulphur, oxygen and hydrogen. It is a colourless, odourless, viscous liquid soluble in water. It is a very important chemical commodity and a nation's sulphuric acid production is a good indicator of its industrial strength.