Please help me with all parts applicable...I dont quite understand. Many Thanks

Question

Please help me with all parts applicable...I dont quite understand. Many Thanks Part A Calculate the pH of 0.250 L of a 0.36 M formic acid-0.30 M sodium formate buffer. Express your answer using three significant figures. Part B After the addition of 0.0050 mol of NaOH. Assume that the volume remains constant. Express your answer using three significant figures. Part C After the addition of 0.0050 mol of HCl. Assume that the volume remains constant. Express your answer using three significant figures.

Explanation / Answer

Part a

[formic acid] = 0.36 M

[sodium formate] = 0.30 M

pKa of formic acid = 3.74

pH = pKa + log ([base conjugate]/[acid])

pH = 3.74 + log(0.30/0.36) = 3.66

Part b

After addition of 0.0050 mol of NaOH

HCOO- + Na+ ? HCOONa

moles of HCOO^- = 0.25 * 0.3 + 0.005 = 0.08

moles of HCOONa = 0.25 * 0.36 - 0.005 = 0.085

pH = pKa + log ([base conjugate]/[acid])

pH = 3.74 + lg(0.08/0.085) = 3.71

Part C

after addition of 0.0050 mol of HCl,

HCOO^- + H^+ ? HCOOH

moles of HCOO^- = 0.25 * 0.3 - 0.005 = 0.07

moles of HCOOH = 0.25 * 0.36 + 0.005 = 0.095

pH = pKa + log ([base conjugate]/[acid])

pH = 3.74 + lg(0.09/0.095) = 3.61

Related Questions

Navigate

• Browse (All)
• Browse P
• Subjects

---