Hardness is defined as the total concentration of divalent cations (primarily Ca2+ and Mg2+ ). On method used bymunicipalities to soften water (i.e., to remove the Ca and Mg ions) is lime - soda softening. In this process, the pH is firstraised by adding lime (CaO) which causes brucite (Mg(OH) 2) to precipitate. In the second step, soda ash (Na2CO3) isadded to cause CaCO3 to precipitate. This problem concerns the removal only of the Mg2+ . The pH of a 250 C✓groundwater containing 10 -4 mo- of Mg2+ is raised to 12 with strong base. No further base is added. What will be theLequilibrium pH and Mg 2+ concentration? Ignore activity corrections and the possible precipitation of species other thanbrucite (Mg(OH) 2) as well as the possible complexation of Mg2+ by ligands other than OH - .

Step 1: Step 2: Step 3: Step 4:

Answered: Hardness is defined as the total…

Principles of Modern Chemistry

8th Edition

ISBN:9781305079113

Author:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Publisher:David W. Oxtoby, H. Pat Gillis, Laurie J. Butler

Chapter15: Acid–base Equilibria

Section: Chapter Questions

Problem 57P

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Consider the titration of HF (K a=6.7104) with NaOH. What is the pH when a third of the acid has been neutralized?
Sketch the titration curve for a weak acid titrated by a strong base. When performing calculations concerning weak acidstrong base titrations, the general two-slep procedure is to solve a stoichiometry problem first, then to solve an equilibrium problem to determine the pH. What reaction takes place in the stoichiometry part of the problem? What is assumed about this reaction? At the various points in your titration curve, list the major species present after the strong base (NaOH, for example) reacts to completion with the weak acid, HA. What equilibrium problem would you solve at the various points in your titration curve to calculate the pH? Why is pH 7.0 at the equivalence point of a weak acid-strong base titration? Does the pH at the halfway point to equivalence have to be less than 7.0? What does the pH at the halfway point equal? Compare and contrast the titration curves for a strong acidstrong base titration and a weak acidstrong base titration.
Marble is almost pure CaCO3. Acid rain has a devastating effect on marble statuary left outdoors. Assume that the reaction which occurs is CoCO3(s)+ H+(aq)Ca2+(aq)+HCO3(aq) Neglecting all other competing equilibria and using Tables 15.1 and 13.2, calculate (a) K for the reaction. (b) the molar solubility of CaCO3 in pure water. (c) the molar solubility of CaCO3 in acid rainwater with a pH of 4.00.
A buffer is prepared using the butyric acid/butyrate (HC4H7O2/C4H7O2)acid-base pair. The ratio of acid to base is 2.2 and Ka for butyric acid is1.54105. (a) What is the pH of this buffer? (b) Enough strong base is added to convert 15% of butyric acid to the butyrate ion. What is the pH of the resulting solution? (c) Strong acid is added to the buffer to increase its pH. What must the acid/base ratio be so that the pH increases by exactly one unit (e.g., from 2 to 3) from the answer in (a)?
A 1.0-L solution that is 4.2 M in ammonia is mixed with 26.7 g of ammonium chloride. a What is the hydroxide-ion concentration of this solution? b 0.075 mol of MgCl2 is added to the above solution. Assume that there is no volume change. After Mg(OH)2 has precipitated, what is the molar concentration of magnesium ion? What percent of the Mg2+ is removed from solution?
The titration of 0.100 M acetic acid with 0.100 M NaOH is described in the text. What is the pH of the solution when 35.0 mL of the base has been added to 100.0 mL of 0.100 M acetic acid?
The following figure represents solutions at various stagesof the titration of a weak acid, HA, with NaOH. (The Na+ions and water molecules have been omitted for clarity.) Towhich of the following regions of the titration curve doeseach drawing correspond: (a) before addition of NaOH,(b) after addition of NaOH but before the equivalencepoint, (c) at the equivalence point, (d) after the equivalencepoint?
A buffer system is prepared by combining 0.603 moles of ammonium chloride (NH4CI) and 0.713 moles of ammonia (NH3). What will the solution pH be if 0.239 moles of the nitric acid (HNO3) is added to the solution. Nitric acid is a strong acid. The K₁ of ammonia is 1.8 x 10-5. (Two decimal places)
Please don't provide handwritten solution .....
A 5.296 g sample of a solid, weak, monoprotic acid is used to make a 100.0 mL solution. 30.00 mL of the resulting acid solution is then titrated with 0.09755 M NaOH. The pH after the addition of 21.00 mL of the base is 5.02, and the endpoint is reached after the addition of 46.38 mL of the base. (a) How many moles of acid were present in the 30.00 mL sample? 0.004524 mol(b) What is the molar mass of the acid?351.1 g/mol(c) What is the pKa of the acid? just need help with part C
A buffer system is prepared by combining 0.506 moles of ammonium chloride (NH4Cl) and 0.720 moles of ammonia (NH3). What will the solution pH be if 0.230 moles of the nitric acid (HNO3) is added to the solution. Nitric acid is a strong acid. The K₁ of ammonia is 1.8 x 10-5. (Two decimal places) Type your answer...
(a) (i) A tap water sample has a hardness of 285 mg/L as CaCO3. What is the predominant form of this hardness at a pH of 7.5?(ii) Provide a balanced chemical reaction showing how this hardness can be removed by the addition of lime (Ca(OH)2).(iii) How much lime is required to precipitate the hardness in 2.5 litres of this tap water? How much calcium carbonate will be precipitated? Assume the reaction is 100% efficient and the solubility of calcium carbonate under these conditions is 40 mg/LAtomic weights:Ca = 40H = 1C = 12 O = 16(b) Explain and discuss the concept of CT values to evaluate the performance of chemical oxidation processes as disinfectants during drinking water treatment.

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