Ammonium $($NH $4+)$ is a weak acid with a pK A of $9\mathrm{.}26$: NH $4+$ NH$3+$ H$+.$

Calculate the moles of ammonia $($NH$3)$ that need to be added to $1$ L of water to obtain a

pH of $10$ at equilibrium. Answer $=6\mathrm{.}510-4$ moles.