Question

A buffer solution is made that is 0.363 M in HClO and 0.363 M in NaClO .

(1) If K_a for HClO is 3.50×10^-8 , what is the pH of the buffer solution?  

(2) Write the net ionic equation for the reaction that occurs when 0.082 mol HCl is added to 1.00 L of the buffer solution.

Use H₃O⁺ instead of H⁺ .

A buffer solution is made that is 0.388 M in HCN and 0.388 M in NaCN.

(1) If K_a for HCN is 4.00×10^-10, what is the pH of the buffer solution?

(2) Write the net ionic equation for the reaction that occurs when 0.114 mol NaOH is added to 1.00 L of the buffer solution.

Please explain how you got this answer!

Answer 1

Q1.

find pH of solution,

HClO and ClO- is present, so there is buffer formation

pH = pKa + log(ClO-/HClO)

pKa = -log(3.5*10^-8) = 7.45

[ClO-] = 0.363 [HClO] = 0.363

substitute in buffer equation

pH = 7.45+ log(0.363/0.363)

pH = 7.45

Q2.

the net ionic equation for 0.082 mol of HCl V = 1 L so

[HClO] = 0.363 + 0.082 = 0.445

[Cl-O] = 0.363 - 0.082 = 0.281

pH = pKa + log(ClO-/HClO)

recalculate pH

pH = 7.45 + log(0.281 /0.445 )

pH = 7.250

net ionic:

ClO-(aq) + H3O+(aq) --> HClO(aq) + H2O(l)