I was able to get the top part easily but my mind has gone blank on reverting th

Question

I was able to get the top part easily but my mind has gone blank on reverting the molar mass. Here's the screen shot.  Please show me how you worked the problem. Thank you.

The flask shown here contains 0.173 g of acid and a few drops of phenolphthaiein indicator dissolved in water. The buret contains 0.180 M NaOH. What volume of base is needed to reach the end point of the titration? Assuming the acid is monoprotic, what is its molar mass? Since molar mass has units of grams per mole, you can calculate the molar mass of a sample by dividing its mass in grams by the number of moles in that sample. The number of moles of monoprotic acid in the flask is equal to the number of moles of NaOH you need to add to reach the equivalence point.

Explanation / Answer

Let the acid be HA

HA + NaOH => NaA + H2O


Moles of HA = moles of NaOH = volume x concentration of NaOH

= 16/1000 x 0.180 = 0.00288 mol


Molar mass of HA = mass/moles of HA

= 0.173/0.00288

= 60.1 g/mol

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