Weak Acid Constant Problem

[silveryhair]

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What is the ionization constant of a weak acid, whose hydronium ion concentration is 3e-5 in an 0.02M solution?

Answer is 4.5e-8

Can someone please show me how they got this answer? Thanks!

 

[nyr201]

What is the ionization constant of a weak acid, whose hydronium ion concentration is 3e-5 in an 0.02M solution?

Answer is 4.5e-8

Can someone please show me how they got this answer? Thanks!

hey ok so, the formula to find H+ conc of a weak acid is:

H+ = square rt of Ka x HA

for this we need Ka so 3e-5= square rt 0.02 x Ka

so u square both sides then it gives u... 9e-10 = .02 x Ka


then u divide 9e-10/2e-2= 4.5e-8 which is Ka

 

[silveryhair]

Thanks a bunch!!! 🙂

 

[DQLEUCD]

Thanks a bunch!!! 🙂

You should also know that if given a weak base, you should be able to find out the pH using the same method. If given Ka instead of Kb, divide Kw by Ka to find Kb and use the same formula to solve for the concentration of the base. Take the log of it to find pOH and subtract it by 14 to find the pH.

 

[nyr201]

You should also know that if given a weak base, you should be able to find out the pH using the same method. If given Ka instead of Kb, divide Kw by Ka to find Kb and use the same formula to solve for the concentration of the base. Take the log of it to find pOH and subtract it by 14 to find the pH.

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