in details Weigh accurately a specified amount of the unknown assigned to you (H

Question

in details Weigh accurately a specified amount of the unknown assigned to you (HA) and record the mass. Transfer this solid quantitatively to a 250 mL Erlenmeyer flask and dilute to 100 mLs with water. Add a few drops of the indicator. Record here the data and calculations you use to determine the mass in grams. Fill the buret with the OH^- solution provided. Record the concentration of the OH^- solution here in molarity units. Add the OH^- solution to the flask containing HA until the endpoint is reached (as demonstrated initially by your TA). Record here the data and calculations you use to determine the volume of OH^- solution added in mLs. Calculate the moles of OH^- required to reach the end-point. Calculate the moles of HA that you put into your flask. Calculate the molar mass of your HA.

Explanation / Answer

we first find moles of OH- used .

This is done by formula moles of OH- = Molarity of base x volume of base used in units of liters ( in burette)

Now the reactionis HA + OH- ---> A- + H2O

since HX reacts with OH- in 1:1 ratio   the moles we get for OH- = moles of HA

thus we have HA acid moles

Now we have formula Moles of acid = Mass of acid taken in grams/ Molar mass of acid

since we will have mass of acid data , we can calculate molar mass form above equation

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