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Chemistry Forums for Students => Physical Chemistry Forum => Topic started by: Beetle on June 15, 2005, 12:23:40 AM

Title: Buffer Solution CH3COOH
Post by: Beetle on June 15, 2005, 12:23:40 AM

What Volume of 0.25M NaOH soln must be added to 125mL of 0.44M CH3COOH solution to give a buffer solution with a pH of 5.40 (Ka CH3COOH = 1.75e-5)

I tried using the buffer solution
pH = pKa + log([A-]/[HA])
and got to
4.3958 = ([A-]/[HA])

but i cant work out where to go from there

Any hints would be wonderful!
Thanx

Title: Re:Buffer Solution CH3COOH
Post by: AWK on June 15, 2005, 02:39:42 AM

write down a neuralization reaction
[A-] = moles_of_NaOH/final_Volume
[HA] = (moles_of_CH3COOH - moles_of_NaOH)/final_Volume
moles_of_CH3COOH = moles_of_A- + moles of_HA

Hence you have a system of equations of type
x/y = A
x+y = B