Use the References to access important values if needed for this question. Equal
ID: 1026942 • Letter: U
Question
Use the References to access important values if needed for this question. Equal volumes of 0.362 M aqueous solutions of acetylsalicylic acid (aspirin) (HC9H704(aq)) and sodium acetate (NaCH3COO) are mixed. artially correct e th e net ionic equation for the overall reaction that takes place as the system comes to equilibrium Write acetic acid, benzoic acid or formic acid and their conjugates in the form RCOOH/RCOO. For example, benzoic acid should be written "C6HsCOOH" NOT "C6HsCO2H". It is not necessary to include states such as (a) (2) What is the value of the equilibrium constant for this reaction? (3) What is the pH of the resulting solution? Use the Tables link on the toolbar for any equilibrium constants that are required.Explanation / Answer
1) general eqn, acetylsalicylic acid+sodium acetate=sodium acetylsalicylate (salt) +acetic acid
balanced equation:C9H7O4H +NaCH3COO --->C9H7O4Na +CH3COOH
ionic equation: C9H7O4H (aq)+ Na+ + CH3COO-(aq) --->C9H7O4- + Na+ +CH3COO- + H+
removing all the spectator ions:
net ionic eqn: C9H7O4H(aq) --->C9H7O4- (aq) +H+(aq)
2)ka aspirin =3.0*10^-4 (acid dissociation constant)
3) ka=[C9H7O4-][H+]/[C9H7O4H]
ICE table
ka=x(0.362+x)/(0.362M-x)=3.0*10^-4
0.362>>>x as kais small(less dissociation)
x(0.362M)/(0.362M)=3.0*10^-4
x=3.0*10^-4=[C9H7O4-]=[H+]
pH=-log [H+]=-log (3.0*10^-4 )=3.5
pH=3.5
[C9H7O4H] [C9H7O4-] [H+] initial 0.362M 0.362M 0 change -x +x +x equilibrium 0.362M-x 0.362+x x
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