Determine the ammonia concentration of an aqueous solution that has a ph of 11.50. the equation for the dissociation of nh3 (k b = 1.8 Ã 10-5) is nh3 (aq) + h2o (l) â nh4 + (aq) + oh - (aq).

Question

Chemistry

Mohamed

15 January, 12:02

Determine the ammonia concentration of an aqueous solution that has a ph of 11.50. the equation for the dissociation of nh3 (k b = 1.8 Ã 10-5) is nh3 (aq) + h2o (l) â nh4 + (aq) + oh - (aq).

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Tate Gray · Answer 1

When PH = 11.5 so, we can get the POH from this formula:

PH + POH = 14

11.5 + POH = 14

∴POH = 2.5

and we can get [OH] from this formula:

POH = - ㏒[OH-]

2.5 = - ㏒[OH-]

∴ [OH] = 0.0032

according to the reaction equation:

NH3 (aq) + H2O (l) ↔ NH4 + (aq) + OH - (aq)

so, Kb = [NH4+][OH] / [NH3]

when [NH4+] = [OH]

by substitution with Kb & [OH]

1.8 x 10^-5 = (0.0032) ^2 / [NH3]

∴ [NH3] = 0.569 M

∴ the concentration of ammonia = 0.569 M