ectionSAL re Lab Questions 1. A certain bufer is made by dissolving NaHCO, and N

Question

ectionSAL re Lab Questions 1. A certain bufer is made by dissolving NaHCO, and Na,CO, in some water. Write the equation to show, how this buffer neutralizes added H+ and OH- H added H addic 2. Calculate the pH of 0.100M propanoic acid(HC,H,O, Ka-13X10) 3. Calculate the pH of 0.10 M HONH, (Kb-1.1x10). 14-4484052 | =_109(328x102) =448 Calculate the pH after 0.020 mole HCI is added to 1.0 L of 0.100 M propanoic acid HC,H502, Ka=13x105. 4. 5. Calculate the pH of 0.1M acetic acid /0.25M Sodium acetate. p0H--10g ( 25) 1002 PH-I9-POH POH- 109.1) 4-1 13 pH

Explanation / Answer

2)

pH of a weak acid is given by pH = 1/2(pKa - log C)

pH = 1/2(-log(13*10^-5) - log(0.1))

pH = 2.443

3)

pOH of a weak base is given by pOH = 1/2(pKb - log C)

pOH = 1/2(-log(1.1*10^-8)-log(0.1))

pOH = 4.48

pH = 14 - pOH

pH = 14 - 4.48 = 9.52

4)

HCl is stron acid so it can dissociates completly into H+ ions and Cl- ions

so concentration of H+ ions from HCl solution = 0.02/1L = 0.02 M

Degree of dissociation x = squre root of ( Ka/C)

Ka = acid dissociation constant

C = concentration of acid

Degree of dissociation x = squre root of(13*10^-5/0.1)

x = 0.0361

so Concentration of H+ ion from HC3H5O2 = 0.0361 * 0.1 = 0.00361

total concentration of H+ ion = 0.02 + 0.00361 = 0.02361

pH = -log(H+)

pH = -log(0.02361)

pH = 1.6269

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