The ammonium ion behaves as a weak acid. Under standard conditions, a $0.300\ \text{mol dm}^{-3}$ ammonium chloride solution has pH $4.89$. Calculate the $[\text{H}^+]$ in a $0.300\ \text{mol dm}^{-3}$ ammonium chloride solution.
Calculate the value of $pK_a$ for the ammonium ion.
A buffer solution may be prepared by combining ammonium chloride and ammonia solution. Explain, using an equation, how this mixture can act as a buffer when a small quantity of strong acid is added.
Explain, using an equation, how this mixture can act as a buffer when a small amount of strong base is added.
Use $K_w$ to find $[\text{H}^+]$ in pure water at standard conditions. Show all working.
At $50\ ^\circ\text{C}$, the pH of pure water is $6.64$. Calculate the numerical value of $K_w$ at $50\ ^\circ\text{C}$.