For the reaction of acetic acid, CH_3COOH, with sodium hydroxide, NaOH, a. write

Question

For the reaction of acetic acid, CH_3COOH, with sodium hydroxide, NaOH, a. write the complete, balanced equation. Label the acid and its conjugate base. b. write the net ionic equation. c. How many acid protons are there in a molecule of acetic acid? What does an acid-base titration accomplish? What is an indicator and how does it function in a titration experiment? By using the proper units for volume and concentration in the titration equation, show that Molest_acid = Molest_base What is the molarity of an unknown acid if 40.5 mL of the acid can be titrated to an end point by 20.5 mL of 0.2250 M NaOH? Show your work and be careful with significant figures.

Explanation / Answer

(1)

a) CH3COOH(aq) + NaOH(aq) -------------> CH3COONa(aq) + H2O(l)

CH3COOH ( acid ) , CH3COO- ( conjugate base )

b) Net ionic : CH3COOH (aq) + OH-(aq) --------------> CH3COO-(aq) + H2O(l)

c) one acid proton is present in CH3COOH.

   ( Hydrogen attached to oxygen is acid proton )

(2) This accomplishes how much acid/base is needed to neutralise a base/acid, thereby concentration of unknown solution can be calculated.

(3) An indicator is a weak (usually organic) acid or base that changes its molecular shape with changes in pH. As the shape changes then the color of the solution changes.

During a titration, when the reaction is completed then indicator color will be changed. And that point is called end point.

(4)

concentration ( mol / L ) x volume (L) = mol

So, ( M x V ) acid = ( M x V ) base

=> moles acid = moles base

(5)

M x ( 40.5 ) = 0.2250 x 20.5

=> M = 0.114 M

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