Chemistry Question

Question

The identity of an unknown monoprotic organic acid is determined by titration. A 0.448 g0.448 g sample of the acid is titrated with 0.176 M NaOH.0.176 M NaOH. What is the molar mass of the compound if 14.1 mL14.1 mL of the NaOHNaOH solution is required to neutralize the sample?

molar mass:

gmolgmol

The compound is 60.0% C,60.0% C, 4.48% H,4.48% H, and 35.5% O.35.5% O. What is the molecular formula of the organic acid?

formula:

Answer 1

1) Monoprotic, so moles of acid = Molarity of NaOH x volume of titrant in liters

2) Molar mass = g of acid/moles of acid

3) Find Empirical formula by taking a basis of 100g of acid and translate all the g of each element to moles.

4) The empirical formula is C_xH_yO₁ with x = carbon moles divided by O moles and y = H moles divided by O moles (This is for the likely case that O is the smallest number of moles. If not divide through by that element's moles). If you get a decimal that looks like a fraction, multiply through by the denominator of the fraction: 1.5 is 3/2 , N₁O_1.5 goes to N₂O₃. (These numbers should be very close (2.9 is not 3.0).

5) Find Molecular mass divided by empirical formula mass. This is the multiplier for the subscripts:

Benzene: MWt = 78 EF is CH with a mass of 13

78/13 = 6 so multiply the subscripts of the empirical formula, CH, by 6 or C₆H₆

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