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anonymous
 one year ago
The compound para–aminobenzoic acid (PABA) is a powerful sun–screening agent whose salts were once used widely in sun tanning and screening lotions. The parent acid, which we may symbolize as H–Paba, is a weak acid with a pKa of 4.92 (at 25 °C). What are the [H+] and pH of a 0.030 M solution of this acid? Please help!!
anonymous
 one year ago
The compound para–aminobenzoic acid (PABA) is a powerful sun–screening agent whose salts were once used widely in sun tanning and screening lotions. The parent acid, which we may symbolize as H–Paba, is a weak acid with a pKa of 4.92 (at 25 °C). What are the [H+] and pH of a 0.030 M solution of this acid? Please help!!

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aaronq
 one year ago
Best ResponseYou've already chosen the best response.1So write an equation for the dissociation of the acid, then use it to write an equilibrium expression. \(\sf pK_A=log(K_A)\)

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0i thought that you would find H+ by multiplying 4.92 and 0.030 and then for the ph you would solve for x?

aaronq
 one year ago
Best ResponseYou've already chosen the best response.1it's not too far off. multiply the Ka by 0.03 then take the squared root, then you have [H+]. Next take the negative logarithm of [H^+] then you have the pH

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0i got .021 for H+? is that right?

aaronq
 one year ago
Best ResponseYou've already chosen the best response.1no it can't be negative

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0okay so would it be .021 then?

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0i did the log of 4.92 and then i multiplied it by the0.030

aaronq
 one year ago
Best ResponseYou've already chosen the best response.1the first step is wrong, the formula is \(\sf pK_A=log(K_A)\), so then \(\sf K_A=10^{pK_A}\)

aaronq
 one year ago
Best ResponseYou've already chosen the best response.1Does that make sense to you? the initial concentration of the acid is 0.030 M

aaronq
 one year ago
Best ResponseYou've already chosen the best response.1no it can't be higher than the concentration of the acid

aaronq
 one year ago
Best ResponseYou've already chosen the best response.1did you do what i said previously? "multiply the Ka by 0.03 then take the squared root, then you have [H+]"

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0yeah you said ka was equal to 10^4.92? and then i multiplied it by 0.030? and then i took the square root of it and got 6.00x10^4

aaronq
 one year ago
Best ResponseYou've already chosen the best response.1yeah, that answer is right

aaronq
 one year ago
Best ResponseYou've already chosen the best response.1it's not what you wrote before though

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0yeah i forgot to take the square root

anonymous
 one year ago
Best ResponseYou've already chosen the best response.0and then for the ph i get 3.22?
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