We are being asked to calculate the Kb of quinine (Q).
Quinine chloride salt dissociates into:
QHCl(aq) + H2O(l)→QH+(aq) + Cl-(aq)
Since we’re dealing with a weak acid and Ka is an equilibrium expression, we will have to create an ICE chart to determine the equilibrium concentration of each species:
• QH+→ weak acid→ proton donor
• H2O→ will act as the weak base→ proton acceptor
Equilibrium reaction: QH+(aq) + H2O(l) ⇌ Q(aq) + H3O+(aq)
We are given 0.23 mole of quinine chloride in 1.0 L solution hence:
Molarity of QH+ = 0.23 M
A solution of 0.23 mol of the chloride salt of protonated quinine (QH+), a weak organic base, in 1.0 L of solution has pH=4.58.
Find the Kb of quinine (Q).
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What scientific concept do you need to know in order to solve this problem?
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