Problem: What is the pH of 0.32 M R-NH2 (amine - a weak base) with a Kb of 6.43x10-6 at 21°C? Enter pH to 2 decimal places.

FREE Expert Solution

Remember that weak bases partially dissociate in water and that bases accept H+ from the acid (water in this case). The dissociation of R-NH2 is as follows:

Equilibrium reaction:        R-NH2(aq) + H2O(l)  R-NH3+(aq) + OH-(aq)


Step 1: Construct an ICE chart for the reaction.


Step 2: Write the Kb expression and calculate for Kb.

Kb=productsreactantsKb=[R-NH3+][OH-][R-NH2]

Solids and liquids are not included in the expression


Step 3: Calculate the equilibrium concentrations.

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Problem Details

What is the pH of 0.32 M R-NH2 (amine - a weak base) with a Kb of 6.43x10-6 at 21°C? Enter pH to 2 decimal places.

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