0. Calculate a reasonable amount (mass in g) of your unknown acid to use for a t

Question

0. Calculate a reasonable amount (mass in g) of your unknown acid to use for a titration. You will want about 30 mL of titrant to get to the equivalence point. Assume that your base is about 0.05 M and that your unknown acid has a molar mass around 400 g/mol. (Report your answer using 2 significant figures) g 1. Refer to figures 1 and 2, and the accompanying text, of the experiment in the coursepack to determine the following values: b. the midpoint volume 5.3 2. What is the pKa of the weak acid titrated. Refer to figure 1 and the appropriate text - How to See Buffering and Find the pKa 5.0 3. Suppose that 21.62 mL of 0.0477 M NaOH was required to titrate 0.386 g of the unknown acid. What is the molar mass of the unknown acid? *g/mol

Explanation / Answer

0. Let us assume x gms of unkown acid is required for titration.

its given its molar mass is 400g/mol

also volume of titrant which is base=30 ml and its concentration =0.05 M

So mole of acid required to reach equivalence point=moles of base given =(30*10-3*0.05)=0.0015 moles

So number of moles =given mass/Molar mass

so x=(400*0.0015)=0.6 gms of unknown acid required to reach equivalence point.

3.Given 21.62 ml of 0.0477 M NaOH is required to titrate 0.386 g of unknown acid.

Moles of NaOH required=Volume in litres *Molarity=(21.62*10-3**0.0477)=1.0312*10-3 moles

For titration,moles of unknown acid=moles of NaOH required=1.0312*10-3 moles

Given mass of unknown acid is 0.386g

number of moles =given mass/Molar mass

so molar mass of acid=0.386/(1.0312*10-3 moles)=374.29g/mol

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