pH = pKa + log ( [ HEPES] / [HEPES protonated] 7.8 = 7.47 + log ( [HEPES] / [HEPES protonated]) 7.8-7.47 = log ( [HEPES] / [HEPES protonated]) [HEPES] / [HEPES protonated] = 10 ^ 0.33 = 2.138 [HEPES] = 2.138 * [HEPES protonated] Given [HEPES] = 0.025M [HEPES protonated] = 0.025/2.138 =0.0117M For preparation of solution amount of HEPES = 0.0117+0.025 = 0.0367 M of HEPES hydrochloride and 0.025 M of Na OH is required 0.0367 M of HEPES hydrochloride and 0.025 M of Na OH is required has to be used Solution pH = pKa + log ( [ HEPES] / [HEPES protonated] 7.8 = 7.47 + log ( [HEPES] / [HEPES protonated]) 7.8-7.47 = log ( [HEPES] / [HEPES protonated]) [HEPES] / [HEPES protonated] = 10 ^ 0.33 = 2.138 [HEPES] = 2.138 * [HEPES protonated] Given [HEPES] = 0.025M [HEPES protonated] = 0.025/2.138 =0.0117M For preparation of solution amount of HEPES = 0.0117+0.025 = 0.0367 M of HEPES hydrochloride and 0.025 M of Na OH is required 0.0367 M of HEPES hydrochloride and 0.025 M of Na OH is required has to be used.