# Chemistry

posted by Raeann

Since the unkown acid is monoprotic, this also equals the number of moles of acid to use. A typical molar mass for an unknown acid in this experiment is 380 g/mol. Using this molar mass, calculate the mass (in grams) of unknown acid you should use per titration.

1.Suppose that 10.2 mL of 0.0512 M NaOH were required to titrate a sample of unkown acid. How many moles of NaOH were used? The answer i got is 0.00052224

2. Assuming that the unknown acid sample in question 1 had a mass of 0.177g, what is the molar mass of the unknown acid?

I tried everything and cant figure out number 2.

1. DrBob222

You leave us in the dark with this. Instead of saying you tried everything, post what you tried and let us find the error. This we're playing guessing games.

2. Raeann

I tried:
0.00052224=0.1777/x
0.00052224=380/x

3. DrBob222

0.177, not 0.1777. Then
0.000522 = 0.177/x
x = 0.177/0.000522 = 338.9 which rounds to 339.

Your line three doesn't follow from line 2. Line 2, except for the extra 7 in the grams is ok. I don't know where the 380 came from. If you had finished and shown how you obtained x I might be more definitive. Sometimes these data bases count the answer incorrect if you use too many significant figures. You are allowed only 3 places. You never actually solved for x so I can't tell where you made the error.

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