Question

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5 – Calculate the concentrations of H+, HCO3- and CO32- in a 0.025 M H2CO3 solution.

6 – Classify the following as a Lewis acid, Lewis base, both or neither:CO2, H2O, I-, SO2, NH3, OH-, H+, BCl37 –

7-Calculate the pH of a solution that is 0.20 M NH3 and 0.30 M NH4Cl.8 –

8-The pH of blood plasma is 7.40. Assuming the principal buffer system is HCO3-/H2CO3, calculate the ratio [HCO3-]/[H2CO3] .

9 – A 0.2688 g sample of a monoprotic acid neutralizes 16.4 mL of a 0.8133 M KOH solution. Calculate the molar mass of the acid.

10 – A 10.0 mL solution of 0.300 M ammonia is titrated with 0.100 M HCl solution. Calculate the pH aft ether following additions of HCl:a) 10.0 mLb) 30.0 mLc) 40.0 mL

11 – Calculate the concentration of I- ions in a solution of AgI with [Ag+] = 9.1 x 10-9 M.

12 – A solution of 0.060 M NaF (75 mL) is mixed with 0.15 M Sr(NO3)2 (25 mL). Calculate the concentrations of each ion after equilibrium is achieved given Ksp for SrF2 = 2.0 x 10-10.Hint: The ion exchange reaction to produce SrF2 can be considered to go to completion before equilibrium is reestablished starting from the products, much as we’ve done for titration calculations at the equivalence point.13 – a) Calculate the molar solubility of hydroxyapatite given Ksp = 2 x 10-59.b) Calculate the molar solubility of hydroxyapatite in a buffered solution of pH 4.0.You’ll need to find the formula for hydroxyapatite and its solvation reaction in order to write the equilibrium constant expression.

Answer 1

5) The ionization that occurs is:

H2CO3 = H + + HCO3-

Ka1 = [H +] * [HCO3-] / [H2CO3]

4.3x10 ^ -7 = X ^ 2 / 0.025

It clears X = 1x10 ^ -4 M

[H +] = [HCO3-] = 1x10 ^ -4 M

You have the second ionization:

HCO3- = H + + CO3-2

It has:

Ka2 = [H +] * [CO3-2] / [HCO3-]

4.8x10 ^ -11 = 1x10 ^ -4 * [CO3-2] / 1x10 ^ -4

It clears [CO3-2] = 4.8x10 ^ -11 M

6) CO2: None

H2O: Both

I-: Base of Lewis

SO2: Lewis Base

NH3: Lewis Base

OH-: Lewis Base

H +: Lewis acid

7) The pH is calculated:

pH = pKa + log [NH3] / [NH4 +] = 9.25 + log (0.2 / 0.3) = 9.10

8) The relationship is calculated:

[HCO3-] / [H2CO3] = 10 ^ (pH - pKa) = 10 ^ (7.4 - 6.4) = 10

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