Neutral solutions are those that have an equal concentration of hydrogen ions (`H^+` ) and hydroxide ions (`OH^-` ) and the concentration of both is equal to `10^-7` M. A solution that is acidic has a concentration of `H^+` ions greater than `10^-7` M and the corresponding concentration of `OH^-` ions is less than `10^-7` M. For a basic solution on the other hand the `H^+` concentration is less than `10^-7` M and the `OH^-` concentration is greater than `10^-7` M.
pH is the negative logarithm of the hydrogen ion concentration. For any solution pH = `-log_10[H^+]` . A neutral solution has a pH value of 7. Solutions with a pH value less than 7 are acidic in nature and the pH value of basic solutions is greater than 7.
Acids and bases undergo different chemical reactions with compounds. For example, acids react with metals to liberate hydrogen gas and react with carbonates to releases water and carbon dioxide. Bases react with most compounds to form hydroxides. In the litmus test bases turn litmus paper blue and acids turn litmus paper red.
We can talk about the acids and bases using the pH scale at room temperature which goes from 0 to 14.
A neutral solution has pH of 7. The hydrogen ion concentration of a neutral solution can be found by using `k_w` , the dissassociation constant of water.
`k_w = [H^+][OH^-]`
At room temperature, `k_w = 1 xx 10^(-14) mol^2dm^(-6)`
In a neutral solution `[H^+] = [OH^-]` . Therefore,
`[H^+] = [OH^-] = 1 xx 10^(-7) moldm^(-3)`
Acids have a pH lower than 7. Depending on how low the number is acids are catgorised into weak acids and strong acids. The hydrogen ion concentration of acids is higher than `1 xx 10^(-7)` and hydroxyl ion concentation is lower than `1 xx 10^(-7)` .
For example: An acid with pH of 3 will have,
`[H^+] = 1 xx 10^(-4)`
`[OH^-] = 1 xx 10^(-10)`
On the other hand, bases have pH higher than 7. Depending on how high the pH value is they are categorised into weak bases and strong bases.
For example: A base with pH value 10 would have,
`[H^+] = 1 xx 10^(-10)`
`[OH^-] = 1 xx 10^(-4)`
Due to this difference in H+ and OH- ions, acids and bases react differently to reactions. Acids react with metals and bases usually react with non-metals.