# We can conclude that the experiment gave a reasonably accurate value for the number of moles of water of crystallization in oxalic acid

by rimarif (student)

Rimsha Arif        IB1-5

Data Collection and Processing

Qualitative Data:

Once the sodium hydroxide solution was in the burette and a certain amount of oxalic acid solution was in the conical flask, along with three drops of phenolphthalein solution to act as an indicator, a few milliliters of the base was added to the acid each time. After every few milliliters, the conical flask would be swirled to ensure whether a color change has taken place or if it is still colorless. Soon, we begin to add a few drops of the NaOH solution into the conical flask and then we began to see a slight change in color. At first there were a few signs of color, but as a few more drops were added, the color became more prominent and showed a tinge of pink. This meant that the right amount of base was added into the acid and from using the results we are able to find the number of moles of water of crystallization in oxalic acid. This experiment was repeated three times with the same variables and measurements to get an average of the readings collected for more accurate results.

Quantitative Data:

Average Volume of NaOH solution: (24.6+24.8+24.7)/3 = 24.7cm³.

Processing of Results:

(COOH)₂.xH₂O (aq) + 2NaOH(aq)                     (COONa)₂ (aq) + 2H₂0(l)

Number of moles of NaOH = = (24.7/1000) x 0.1 = 0.00247

Number of moles of (COOH) ₂ = 0.00247/2 = 0.001235

Number of moles of (COOH)₂ in 250 cm3 =( 0.001235/25.0) x 250 = 0.01235

Mr of (COOH)₂.xH₂O = =1.5/0.1235 =121.457 = 121

Mr of (COOH)₂.xH₂O = 2(12.01+16+16+1.01) + 18x = 90.04 + 18x

x = (121-90.04)/18 = 1.72

Uncertainties:

Uncertainty in mass of oxalic acid crystals= ...