Question

Part 1:

What is the pH of a neutral substance?



Part 2:

If a substance has a pH of 2, is it acidic or basic? What is one tool that you can use to indicate whether a substance is an acid or base?

Answer 1

\[pH = -\log[H ^{+}]\]

In water solutions concentration of hydrogen cations is rather small. Water has a dissociation constant \[K _{w}=[H ^{+}][OH ^{-}]=14\] corresponding to the equation \[H _{2}O \leftarrow \rightarrow H ^{+}+OH ^{-}\]

This means that concentration is very low, it is not convenient to say it is \[10 ^{-8}\] or something like that. That's why we take the logarithm of the concentration - the power to which number ten is raised.

pH = 7 means that the concentration is \[10^{-7}\]

Due to the magnitude of Kw, it is obvious that the sum of the concentrations of hydrogen and hydroxide ions has to be equal at all times.

pH + pOH = 14

So, pH = 7 when concentrations of H and OH are equal, so the solution is neutral.

pH = 2 means that the concentration of hydrogen cations is much larger than that of hydroxide ions - it is \[10^{-2}\]. There's a large excess of them, so the solution is acidic.

Answer 2

part-1 Neutral substance has 7 pH value.
part -2 Substance which have below 7pH value consider as acidic in nature and above are basic so 2 is smaller than 7 means substance is acdic in nature. And tool to measure pH value we use litmus paper

Answer 3

Neutral substance has a pH of 7 AT STANDARD TEMP.