Question

Give the conditions for a neutral aqueous solution at$\text{25}°\text{C}$ , in terms of$\left[{\text{H}}^{\text{+}}\right]$ , pH, and the relationship between $\left[{\text{H}}^{\text{+}}\right]$and $\left[{\text{OH}}^{-}\right]$. Do the same for an acidic solution and for a basic solution. As a solution becomes more acidic, what happens to pH, pOH,$\left[{\text{H}}^{\text{+}}\right]$ , and$\left[{\text{OH}}^{-}\right]$ ? As a solution becomes more basic, what happens to pH, pOH, $\left[{\text{H}}^{\text{+}}\right]$and$\left[{\text{OH}}^{-}\right]$ ?

Short answer

For a solution to be neutral at$25°\text{C}$,$\text{pH}\text{=}\text{7}$

For neutral solution:data-custom-editor="chemistry" $\left[{\text{H}}^{\text{+}}\right]=\left[{\text{OH}}^{-}\right]$

For acidic solution:$\left[{\text{H}}^{\text{+}}\right]>\left[{\text{OH}}^{-}\right]$,$\text{pH}<\text{7,}\text{pOH}$

For basic solution: $\left[{\text{H}}^{\text{+}}\right]<\left[{\text{OH}}^{-}\right]$, $\text{pH}>\text{7,}\text{pOH}<\text{7}$

Step-by-step solution

Neutral Aqueous Solution

For a solution to be neutral at $25°\text{C}$, because at $25°\text{C}$

$\left[{\text{H}}^{\text{+}}\right]=\left[{\text{OH}}^{-}\right]=1.{\text{0×10}}^{\text{- 7}}\text{mol/L}$

When the concentrations of ${\text{H}}^{\text{+}}$ and ${\text{OH}}^{-}$ ions is equal then the solution is neutral.

Acidic Aqueous Solution

For a solution to be acidic, the$\left[{\text{H}}^{\text{+}}\right]>\left[{\text{OH}}^{-}\right]$.

pH scale is 0-14 and for acidic solution pH is lower than 7. For strong acids its near 0 and for weak acid its near but below 7.

As the solution becomes more and more acidic, ${\text{H}}^{\text{+}}$ ion concentration increases, ${\text{OH}}^{-}$ ion concentration decreases, value of pH decreases and value of pOH increases.

Basic Aqueous Solution

For a solution to be basic, the$\left[{\text{H}}^{\text{+}}\right]<\left[{\text{OH}}^{-}\right]$

pH scale is 0-14 and for a basic solution pH is greater than 7. For strong bases its near 14 and for weak base its near but above 7.

As the solution becomes more and more basic, ${\text{H}}^{\text{+}}$ion concentration decreases, ${\text{OH}}^{-}$ ion concentration increases, value of pH increases and value of pOH decreases.