The pKs of succinic acid are 4.21 and 5.56. How many grams of monosodium succina

Question

The pKs of succinic acid are 4.21 and 5.56. How many grams of monosodium succinate (140g/mol) and disodium succinate (162 g/mol) must be added to 1L of water to produce a solution with pH 5.28 and a total solute concentration of 100mM assuming the total volume remains 1L?

A) 14.9g monosodium succinate, 1.1g disodium succinate

B) 11.3g monosodium succinate, 4.2g disodium succinate

C) 4.9g monosodium succinate, 9.8g disodium succinate

D) 9.7g monosodium succinate, 4.9g disodium succinate

please show calculations

Explanation / Answer

pH of acidic buffer = pka+log(disodium succinate/monosodium succinate)

           pka of monosodium succinate =   5.56

5.28 = 5.56 + log(x)

x = 0.525

disodium succinate/monosodium succinate = x = 0.525

total buffer = 100*10^-3*1 = 0.1 mol

disodium succinate + monosodium succinate = 0.1

   y*0.525 + y = 0.1

y = No of mol of monosodium succinate = 0.0656 mol

Amount of monosodium succinate = 0.0656*140 = 9.2 g

No of mol of disodium succinate = 0.1-0.0656 = 0.0344 mol

Amount of disodium succinate = 0.0344*162 = 5.6 g

answer: D

Related Questions

Navigate

• Browse (All)
• Browse T
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.