Write the complete dissociation equilibria as well as all K, expressions (one fo
ID: 952450 • Letter: W
Question
Write the complete dissociation equilibria as well as all K, expressions (one for each individual dissociation reaction) for the acids shown below. Sulfurous acid, H_2SO_3 Propanoic acid, CH_3CH_2COOH A solution of a weak base has a pH of 11.85. If the pK_b for the base is 4 50, what is the molar concentration of the base? Calculate the pH of a 1.0 M solution of sodium formate. Formate ion is the conjugate base of formic acid. Formic acid has a K_a value of 1.7 Times 10^-4. Remember that you will need to determine K_b for formate ion. Calculate the pH of a 2.80 M solution of ammonium nitrate. The K_b for ammonia is 1.8 Times 10^-5. Remember that you will need to determine K_a for ammonium ion.Explanation / Answer
15 )
H2SO3 < ------------------------> H+ + HSO3- , Ka1
Ka1 = [HSO3-] [H+] / [H2SO3]
HSO3- <---------------------> SO3-2 + H+
Ka2 = [SO3-2] [H+] / [HSO3-]
B)
CH3CH2COOH <---------------------> CH3COO- + H+
Ka = [CH3CH2COO-][H+]/[CH3CH2COOH]
16)
pH = 11.85
pKb = 4.50
pH + pOH = 14
pOH = 2.15
pOH = 1/2 [pKb - logC]
2.15 = 1/2 (4.50 -logC)
log C = 0.2
C = 1.58 M
concnetration of base = 1.58 M
17 )
sodium formate is the weak acid strong base salt so pH > 7
C = 0.1 M
Ka = 1.7 x 10^-4
pKa = 3.77
pH = 7 + 1/2 [pKa + logC]
pH = 7 + 1/2 [3.77 + log 0.1]
pH = 8.38
18)
NH4NO3 is the weak base strong acid salt so pH <7
pKb = 4.74
pH = 7 - 1/2 [pKb + logC]
pH = 7 - 1/2 [4.74 + log2.80]
pH = 4.41
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