In this experiment, you will be determining the equivalent weight of maleic and

Question

In this experiment, you will be determining the equivalent weight of maleic and fumaric acid. Like the acids that you will be studying in lab, H2SO4 also is a diprotic acid. What is its equivalent weight?

98.09 g/mol

98.09 g/eq

49.04 g/mol

49.04 g/eq

A.

98.09 g/mol

B.

98.09 g/eq

C.

49.04 g/mol

D.

49.04 g/eq

1. Standardize the NaOH solution with KHP, if necessary, as before. Clean a buret. Rinse with DI water, then with a little of the 0.05 M NaoH. Fill the buret NaoH. Make sure the tip of the buret has been rinsed with the NaoH and record the initial buret reading. Use -0.2 g of KHP in 50 mL of water for each trial with 3-4 drops of phenolphthalein as an indicator. Repeat in triplicate and record your observations in Data Table 1. 2. In a 100-mL volumetric flask, add 75 mL of DI water to approximately 0.2 g (record the exact mass of your sample) of maleic acid (repeat for fumaric acid). Mix well to dissolve all of the acid. Then fill the flask to the mark using a pipet. Record your measurements in Data Table 2. 3. Transfer exactly 25 mL of solution with a pipet to a clean 150-mL beaker containing a stirring bar and add 25 mL of DI water from a graduated cylinder 4. Prepare the PASCO pH probe as in previous experiments. 5. Titrate the maleic acid sample. Add sodium hydroxide in small increments that raise the pH about 0.15 units. Record the pH and buret readings in your notebook until the pH levels off. Record your results in Data Table 3. 6. Repeat this entire procedure with the fumaric acid. Record your results in Data Table 4. Record your observations in your laboratory notebook: did you observe what you expected for this titration? what are the similarities and differences for this trial compared to your maleic acid titration?

Explanation / Answer

Maleic acid(C4H4O4) molar mass = (4* atomic mass of C)+(4*atomic mass of H)+(4*Atomic mass of O)

= (4*12)+(4*1)+(4*16)= 116 g/mol

Maleic acid is diprotic acid thus acidity =2

Equivalent weight of maleic acid = molar mass/ acidity = 116/2 =58 g/eq

Fumaric acid (C4H4O4) molar mass= (4* atomic mass of C)+(4*atomic mass of H)+(4*Atomic mass of O)

= (4*12)+(4*1)+(4*16)= 116 g/mol

Fumaric acid is diprotic acid thus acidity =2

Equivalent weight of Fumaric acid = molar mass/ acidity = 116/2 =58 g/eq

Sulphuric acid (H2SO4) molar mass= (2* atomic mass of H)+(1*atomic mass of S)+(4*Atomic mass of O)

= (2*1)+(1*32)+(4*16)= 98 g/mol

Sulphuric acid is diprotic acid thus acidity =2

Equivalent weight of Sulphuric acid = molar mass/ acidity = 98/2 =49 g/eq

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