Answer
It is necessary 0.163g of KOH.
Work Step by Step
1. Calculate the hydroxide ion concentration:
pH + pOH = 14
11.56 + pOH = 14
pOH = 2.44
$[OH^-] = 10^{-pOH}$
$[OH^-] = 10^{- 2.44}$
$[OH^-] = 3.631 \times 10^{- 3}M$
- Since KOH is a strong base, $[KOH] = [OH^-] = 3.631 \times 10^{- 3}M$
2. Calculate the number of moles:
- 800ml = 0.8L
$n(moles) = concentration(M) * volume(L)$
$n(moles) = 3.631\times 10^{- 3} * 0.8$
$n(moles) = 2.905\times 10^{- 3}$
3. Find the mass value in grams:
39.1* 1 + 16* 1 + 1.01* 1 = 56.11g/mol
$mass(g) = mm(g/mol) * n(moles)$
$mass(g) = 56.11 * 2.905\times 10^{- 3}$
$mass(g) = 0.163$
