Question

At $373K$ temperature, the $pH$ of pure water can be:
A. $< 7$
B. $> 7$
C. $= 7$
D. $= 0$

Answer 1

In chemistry, the $pH$ is a scale used to specify the acidity or basicity of an aqueous solution. The acidic solutions (solutions with higher concentrations of ${H^ + }$ ions) are measured to have lower $pH$ values than basic or alkaline solutions

Complete step by step 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 of hydrogen ions in the solution. This means higher the concentration of protons or hydrogen ions of a solution, the lower the $pH$of the solution. The $pH$of pure water is equal to 6 at a temperature of $373K$. All the experiments in the laboratory are performed at room temperature which is taken as $25\;^\circ C$. But when the water is boiled at $100\;^\circ C$, there is a decrease in the $pH$ due to less availability of protons in the boiled water.

So, the correct answer is Option A.

Note:
At the room temperature ($25\;^\circ C$ ), 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 $pH$ scale is traceable to a set of standard solutions whose $pH$ is established by international agreement. Primary $pH$ standard values are determined using a concentration cell with transference, by measuring the potential difference between a hydrogen electrode and a standard electrode such as the silver chloride electrode.