What is a polyprotic acid? What is a polyprotic base? If 25.1mL of 0.1222 N NaOH

Question

What is a polyprotic acid? What is a polyprotic base? If 25.1mL of 0.1222 N NaOH is required to reach the first equivalence point of a solution of citric acid (H_3C_3H_5O_7), how many mL of NaOH are required to completely neutralize this solution? What is the molarity of a 12 N H_2C_2O_6 solution? How many moles and how many equivalents of H_2O^+ are present in 50mL of a 0.3 N solution of H_2SO_4? Why is it necessary to standardize a pH meter or the pH probe? If the pH at one-half the first and second equivalence points of a dibasic acid is 3.20 and 7.45, respectfully, what are the values for pK_a1 and pK_a2 ? From pK_a1 and pK_a2. calculate the k_a1 and k_a2. Derive the relationship between pH and pK_a at one-half the equivalence point for the titration of a weak acid with a strong base. Could K_b for a weak base be determined in the same way that K_a for a weak acid is determined in this experiment? What is the relationship of the successive equivalence point volumes in the titration of a polyprotic acid? The titration of a weak acid with NaOH showed two equivalence points. Using only this information determine the relationship between the molarity and normality of this acid solution. Write the color of indicators and its pH ranges

Explanation / Answer

2. This is calculated from the titration equation of citric acid C6H8O7 or H3C6H5O7

3NaOH (aq) + C6H8O7 (aq) =  Na2C6H5O7 (aq) + 3H2O

So there will be three times of NaOH will require for titrating citric acid, which is 3 x 25.1 ml = 75.3ml

3. This is calculated from the formula: Normality = N, Molarity M= M, number of equivalents=NE

N = M x NE

Here number of equivalents is two because number of equivalents is number of H+ ions can be generated so:

N = M x NE

12=M x 2 = M =12/2 = 6

4. Molarity = moles of solutes/ liters of solution, NE is 2 for H2SO4.

M from 2nd question= 0.15 for 50ml, now for 1L = (0.15x 1000)/50 =3M

moles of solutes = Molarity x liters of solution = 3 x 1 = 3 moles.

5. PH meter is necessary to standardize because all pH scale is start from 1 to 14 and can be calculated by only the base line of pH7. So it is necessary to keep pH meter at caliberated level to calculate the distilled water pH which is 7.

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