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Chemistry Forums for Students => High School Chemistry Forum => Topic started by: 777888 on January 02, 2005, 10:04:34 PM

Title: titration calculation(2)
Post by: 777888 on January 02, 2005, 10:04:34 PM

If 24.5mL of Ca(OH)2 with a concentration of 0.025 mol/L is required to neutralize 35.5mL of acetate acid using a phenolpthalein endpoint. What is the concentration of the acid?

2HC2H3O2 + Ca(OH)2 -> 2H2O + CaC2H3O2

mol Ca(OH)2=0.0245 x 0.025=0.0006125mol

mol HC2H3O2=2 x 0.0006125=0.0001225

[HC2H3O2]=0.0001225 / 0.0355=0.003450704mol/L=0.035 mol /L

Did I calculate it right?

Thanks!

Title: Re:titration calculation(2)
Post by: 777888 on January 04, 2005, 03:33:05 AM

Do I have to care about the weak acid? Do I need any equilibrium calculations in this question?


Besides, 0.025 mol/L has 2 significant digits...

Title: Re:titration calculation(2)
Post by: Donaldson Tan on January 04, 2005, 04:58:21 AM

for titration, you work out that the reaction goes to completion, regardless it's a weak or strong acid. ok. i didn't see the 2significant-figure 0.025. you are right that it should be 2sf.