Question

What is the pH of 0.63% nitric acid solution ? (a) 1 (b) 2 (c) 3 (d) 4

Answer 1

In chemistry, pH denoting 'potential of hydrogen' or 'power of hydrogen' . pH is a scale used to specify the acidity or basicity of an aqueous solution . Acidic solutions (solutions with higher concentrations of H+ ions) are measured to have lower pH values than basic or alkaline solutions.

Complete answer:
The pH scale is logarithmic and inversely indicates the concentration of hydrogen ions in the solution. This is because the formula used to calculate pH approximates the negative of the base 10 logarithm of the molar concentration[a] of hydrogen ions in the solution. More precisely, pH is the negative of the base 10 logarithm of the activity of the H+ ion. At 25 °C, solutions with a pH less than 7 are acidic, and solutions with a pH greater than 7 are basic. Solutions with a pH of 7 at this temperature are neutral (e.g. pure water). The neutral value of the pH depends on the temperature – being lower than 7 if the temperature increases. The pH value can be less than 0 for very strong acids, or greater than 14 for very strong bases. The calculation of the pH of a solution containing acids and/or bases is an example of a chemical speciation calculation, that is, a mathematical procedure for calculating the concentrations of all chemical species that are present in the solution. The complexity of the procedure depends on the nature of the solution. For strong acids and bases no calculations are necessary except in extreme situations. The pH of a solution containing a weak acid requires the solution of a quadratic equation. The pH of a solution containing a weak base may require the solution of a cubic equation. The general case requires the solution of a set of non-linear simultaneous equations. $M = \dfrac{n}{V}\; = \dfrac{w}{{mm \times V}}$ mm = molar mass, V = volume, w = weight of solution, M = molarity, n = number of moles . $\to \dfrac{{{\text{0}}{\text{.63x1000}}}}{{63}}$ $\to 0.01mol{L^{ - 1}}$ $[{H^ + }] = [HN{O_3}] = {10^{ - 2}}mol{L^{ - 1}}$ ${\text{ pH = - log(}}{{\text{H}}^ + }{\text{)}}$ ${\text{ = - log(1}}{{\text{0}}^{ - 2}}{\text{) = - ( - 2)log10}}$ $\to {\text{PH = 2}}$

Note:
The term pH refers to the "potential of hydrogen ions . Sorensen defined pH as the negative of the logarithm of the concentration of hydrogen ions. In terms of hydronium ion concentration, the equation to determine the pH of an aqueous solution is: ${\text{ pH = - log(}}{{\text{H}}^ + }{\text{)}}$