Question

pH of pure water is _ _ _ _ _ _ _ _
A. $0$
B. $1$
C. $7$
D. $14$

Answer 1

Hint: To a very small but very important extent, water is a weak acid that ionizes to hydrogen and hydroxide ions. This equilibrium reaction has the equation: .
Formula used : , $\left[ {{H^ + }} \right] = \left[ {O{H^ - }} \right] = 1\; \times \;{10^{ - 7}}M$ and $pH = - \log 10[H + ]$

Complete answer:

Pure water all by itself is always neutral pH, neither acidic or basic. Water molecules must always ionize to H+ and OH- in equal amounts. The H+ and OH- ion concentrations will be the same .
The neutral pH of water is $7.0$ at about ${25^ \circ }C$ or about ${77^ \circ }F$.
The very tiny fraction of water molecules that ionize in a volume of water varies with temperature. As the temperature goes up molecules get more active and ionize more.
The “neutral pH” of pure water becomes less than $7$ at temperatures above ${25^ \circ }C$(the concentration of [H+] ion increases) and greater than $7$ at colder temperatures below ${25^ \circ }C$(the concentration of [H+] ions decreases)
The “pH” is a measure of the [H+] ion concentration at a given temperature . The pH is a clever way to change very small numbers into a number scale from $0$ to $14$ and is given by this equation .
$pH = - \log 10[H + ]$
Because of this variation of pH with temperature , to be accurate a reference temperature must always be included when reporting pH values.

Note: A neutral solution is one that is neither acidic nor basic. The hydrogen ion concentration equals the hydroxide ion concentration, and both equal $1\; \times \;{10^{ - 7}}M$. In a neutral solution, the, $pH = pOH = 7$. The hydrogen ion concentration is greater than $1\; \times \;{10^{ - 7}}M$ and the hydroxide ion concentration is less than $1\; \times \;{10^{ - 7}}M$. In terms of $pH$, an article solution has a $pH$ less than 7.