Question

Which of the following statements about pH and ${{\text{H}}^{\text{+}}}$ ion concentration is incorrect?
(A) Addition of one drop of concentrated HCI in $N{{H}_{4}}OH$ solution decreases pH of the solution
(B) A solution of the mixture of one equivalent of each of $C{{H}_{3}}COOH$ and NaOH has a pH of 7
(C) pH of pure neutral water is not zero
(D) A cold and concentrated ${{H}_{2}}S{{O}_{4}}$ has lower H+ ion concentration than a dilute solution of ${{H}_{2}}S{{O}_{4}}$

Answer 1

pH is a scale used in chemistry to describe the acidity or basicity of an aqueous solution. Acidic solutions (those containing a larger concentration of ${{H}^{+}}$ ions) have a lower pH than basic or alkaline solutions.
The pH scale is logarithmic, indicating the concentration of hydrogen ions in a solution in inverse order. Because the pH formula approximates the negative of the base 10 logarithm of the molar concentration of hydrogen ions in the solution, this is the case.

Complete Step By Step Answer:
At $25\text{ }{}^\circ C$ , acidic solutions have a pH less than 7, while basic solutions have a pH greater than 7. At this temperature, pH 7 solutions are neutral (e.g. pure water). The pH neutral value changes with temperature, becoming lower than 7 as the temperature rises. For highly strong acids, the pH value can be less than 0 and for very strong bases, it can be more than 14.
The pH scale may be traced back to a collection of standard solutions whose pH has been agreed upon internationally. The potential difference between a hydrogen electrode and a standard electrode, such as the silver chloride electrode, is measured in a concentration cell with transference to derive primary pH standard values. A glass electrode with a pH metre, or a color-changing indicator, can be used to determine the pH of aqueous solutions. pH measurements are useful in chemistry, agronomy, medicine, water treatment, and a variety of other fields.
Because $C{{H}_{3}}COOH$ is a weak acid and NaOH is a strong base, one equivalent of $C{{H}_{3}}COOH$ cannot neutralise one equivalent of NaOH. As a result, a solution containing one equivalent of each does not have a pH of 7. Because NaOH is a strong base, its pH will be on the basic side. As a result, the concentration of OH will be greater than the concentration of ${{H}^{+}}$ .
Hence option B and D are correct.

Note:
By utilising the fact that indicators' colour varies with pH, they may be utilised to monitor pH. The colour of a test solution may be visually compared to a standard colour chart to obtain a pH reading that is accurate to the nearest whole integer. A universal indicator is made up of a combination of indicators that produces a continuous colour shift from pH 2 to pH 10. Universal indicator paper is made out of absorbent paper impregnated with universal indicator. An electronic pH metre is another option for monitoring pH.