Chemistry: The Molecular Nature of Matter and Change
Chemistry: The Molecular Nature of Matter and Change
8th Edition
ISBN: 9781259631757
Author: Martin Silberberg Dr., Patricia Amateis Professor
Publisher: McGraw-Hill Education
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Chapter 19, Problem 19.142P

(a)

Interpretation Introduction

Interpretation:

Species among H2CO3, HCO3-, CO32- having highest concentration at pH=8.5 has to be calculated.

Concept introduction:

pH:

pH is a scale used to specify the acidity or basicity a solution.  It ranges from 014.  pH 7.0 is considered as neutral solution, pH more than 7.0 is taken as basic solution whereas pH less than 7.0 is considered as acidic solution (at 25οC).  It is the measurement of activity of free H+ and OH- in solution.

pKa:

pKa is the negative log of acid dissociation constant that determines the strength of the acid. Lower the pKa value stronger is the acid.

pKa1 is the 1st dissociation constant for the acid and pKa2 is the 2nd dissociation constant of the acid.

(a)

Expert Solution
Check Mark

Answer to Problem 19.142P

Among all the three species, HCO3- is more at pH=8.5.

Explanation of Solution

The equation considered as,

  H2CO3H++HCO3-...(Ka1)

  HCO3-H++CO32-...(Ka2)

  pKa=logKa

Now, for the 1st equation,

  H2CO3H++HCO3-...(Ka1)

  Ka1=4.5×107

  pKa1=log(4.5×107)

  pKa1=6.4368

Now, for the 2nd equation,

  HCO3-H++CO32-...(Ka2)

  Ka2=4.7×1011

  pKa2=log(4.7×1011)

  pKa2=10.3279

From the above data it is shown that, pKa2>pH but pKa1<pH. (pH=8.5 given)

If pKa1 is less that means Ka1 value is more which means the 1st dissociation occurs rapidly and hence HCO3- will be more in medium (as the pH is basic so the conjugate base is more in concentration.)

Again, pKa2 is more that means Ka2 is less and hence 2nd dissociation is slower in rate. Hence in medium the reactant i.e. HCO3- will be more.

Hence among all the three species HCO3- is more at pH=8.5.

(b)

Interpretation Introduction

Interpretation:

At pH=8.5 the concentration ratio of [HCO3-][H2CO3] and [CO32-][HCO3-] has to be calculated.

Concept introduction:

pH:

pH is a scale used to specify the acidity or basicity a solution. It ranges from 014. pH 7.0 is considered as neutral solution, pH more than 7.0 is taken as basic solution whereas pH less than 7.0 is considered as acidic solution (at 25οC). It is the measurement of activity of free H+ and OH- in solution.

pKa:

pKa is the negative log of acid dissociation constant that determines the strength of the acid. Lower the pKa value stronger is the acid.

pKa1 is the 1st dissociation constant for the acid and pKa2 is the 2nd dissociation constant of the acid.

Henderson-Hasselbalch Equation:

This equation is used to determine the pH of a buffer solution.  Ka is the given quantity which is acid dissociation constant. It is done for a given concentration of acid and its conjugate base.

  pH=pKa+log[salt][acid]

(b)

Expert Solution
Check Mark

Answer to Problem 19.142P

The value of concentration ratios of [HCO3-][H2CO3] and [CO32-][HCO3-] are respectively 1.4×102 and 1.48×102.

Explanation of Solution

The equation considered as,

  H2CO3H++HCO3-...(Ka1)

  HCO3-H++CO32-...(Ka2)

  pKa=logKa

For the 1st equation,

  H2CO3H++HCO3-...(Ka1)

Thus the pKa is calculated as,

  Ka1=4.5×107

  pKa1=log(4.5×107)

  pKa1=6.4368

Thus the pH is calculated as,

  pH=pKa+log[salt][acid]

  pH=pKa1+log[HCO3-][H2CO3]8.5=6.35+log[HCO3-][H2CO3]

The value of concentration ratios of [HCO3-][H2CO3]=1.4×102

For the 2nd equation,

  HCO3-H++CO32-...(Ka2)

Thus the pKa is calculated as,

  Ka2=4.7×1011

  pKa2=log(4.7×1011)

  pKa2= 10.33

Thus the pH is calculated as,

  pH=pKa2+log[CO32-][HCO3-]8.5=10.33+log[CO32-][HCO3-][CO32-][HCO3-]=1.48×102

The value of concentration ratios of [CO32-][HCO3-]=1.48×102

Thus the value of concentration ratios of [HCO3-][H2CO3] and [CO32-][HCO3-] are respectively 1.4×102 and 1.48×102.

(c)

Interpretation Introduction

Interpretation:

Reason for lower pH at deep sea level has to be interpreted.

Concept introduction:

pH:

pH is a scale used to specify the acidity or basicity a solution. It ranges from 014. pH 7.0 is considered as neutral solution, pH more than 7.0 is taken as basic solution whereas pH less than 7.0 is considered as acidic solution (at 25οC). It is the measurement of activity of free H+ and OH- in solution.

Photosynthesis:

The process of photosynthesis occurs in plants for their survival.  In this process carbon dioxide is absorbed from nature and oxygen is released to nature by plants.  Sunlight is the main important component for photosynthesis to occur.  Here glucose is formed.

  6CO2+6H2OsunlightC6H12O6+6O2

Respiration:

Respiration is a biochemical process in which in the cells of organisms energy is evolved due to reaction between oxygen and glucose and by this process carbon dioxide is released along with water and ATP

  C6H12O6+6O26CO2+6H2O+ATP

(c)

Expert Solution
Check Mark

Explanation of Solution

The acidity of the sea water is due to presence of dissolved carbon dioxide in the water.

On the upper sea level there are plants and also on upper level of sea sunlight can enter. As a result of that on the upper level of sea photosynthesis occurs and according to the process of photosynthesis carbon dioxide is taken up by plants.  This results a decrease in the dissolved carbon dioxide concentration in the upper sea level.

But still due to the respiration by the sea animals and the plants at upper level there will be some amount of dissolved carbon dioxide in the upper level. So sea water at upper level is acidic but less in amount.

However, in deep sea level, pH=7.5 that means water is more acidic here.  In deep sea level pressure is very high and sunlight cannot enter and thus plants cannot survive there but some animals only can survive there.  Hence photosynthesis does not occur there only respiration occurs.  As a result of that the concentration of dissolved carbon dioxide is more in the deep-sea level than in the upper level.  So the acidity here is more.

Hence, deep sea water has a higher acidity the value of pH=7.5.

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Chapter 19 Solutions

Chemistry: The Molecular Nature of Matter and Change

Ch. 19.3 - Prob. 19.6AFPCh. 19.3 - Prob. 19.6BFPCh. 19.3 - Prob. 19.7AFPCh. 19.3 - Prob. 19.7BFPCh. 19.3 - Prob. 19.8AFPCh. 19.3 - Prob. 19.8BFPCh. 19.3 - Prob. 19.9AFPCh. 19.3 - Prob. 19.9BFPCh. 19.3 - Prob. 19.10AFPCh. 19.3 - Prob. 19.10BFPCh. 19.3 - Prob. 19.11AFPCh. 19.3 - Prob. 19.11BFPCh. 19.3 - Prob. 19.12AFPCh. 19.3 - Prob. 19.12BFPCh. 19.3 - An environmental technician collects a sample of...Ch. 19.3 - A lake that has a surface area of 10.0 acres (1...Ch. 19.4 - Cyanide ion is toxic because it forms stable...Ch. 19.4 - Prob. 19.13BFPCh. 19.4 - Prob. 19.14AFPCh. 19.4 - Calculate the solubility of PbCl2 in 0.75 M NaOH....Ch. 19 - Prob. 19.1PCh. 19 - Prob. 19.2PCh. 19 - Prob. 19.3PCh. 19 - Prob. 19.4PCh. 19 - Prob. 19.5PCh. 19 - Prob. 19.6PCh. 19 - Prob. 19.7PCh. 19 - Prob. 19.8PCh. 19 - Does the pH increase or decrease with each of the...Ch. 19 - The scenes below depict solutions of the same...Ch. 19 - The scenes below show three samples of a buffer...Ch. 19 - What are the [H3O+] and the pH of a propanoic...Ch. 19 - What are the [H3O+] and the pH of a benzoic...Ch. 19 - Prob. 19.14PCh. 19 - Prob. 19.15PCh. 19 - Prob. 19.16PCh. 19 - Find the pH of a buffer that consists of 0.95 M...Ch. 19 - Prob. 19.18PCh. 19 - Prob. 19.19PCh. 19 - Prob. 19.20PCh. 19 - Find the pH of a buffer that consists of 0.50 M...Ch. 19 - A buffer consists of 0.22 M KHCO3 and 0.37 M...Ch. 19 - A buffer consists of 0.50 M NaH2PO4 and 0.40 M...Ch. 19 - What is the component concentration ratio,...Ch. 19 - Prob. 19.25PCh. 19 - Prob. 19.26PCh. 19 - Prob. 19.27PCh. 19 - Prob. 19.28PCh. 19 - A buffer that contains 0.40 M of a base, B, and...Ch. 19 - A buffer that contains 0.110 M HY and 0.220 M Y−...Ch. 19 - A buffer that contains 1.05 M B and 0.750 M BH+...Ch. 19 - A buffer is prepared by mixing 204 mL of 0.452 M...Ch. 19 - A buffer is prepared by mixing 50.0 mL of 0.050 M...Ch. 19 - Prob. 19.34PCh. 19 - Prob. 19.35PCh. 19 - Prob. 19.36PCh. 19 - Choose specific acid-base conjugate pairs to make...Ch. 19 - An industrial chemist studying bleaching and...Ch. 19 - Oxoanions of phosphorus are buffer components in...Ch. 19 - The scenes below depict the relative...Ch. 19 - Prob. 19.41PCh. 19 - What species are in the buffer region of a weak...Ch. 19 - Prob. 19.43PCh. 19 - Prob. 19.44PCh. 19 - Prob. 19.45PCh. 19 - Prob. 19.46PCh. 19 - Prob. 19.47PCh. 19 - Prob. 19.48PCh. 19 - Prob. 19.49PCh. 19 - Prob. 19.50PCh. 19 - Prob. 19.51PCh. 19 - Prob. 19.52PCh. 19 - Prob. 19.53PCh. 19 - Prob. 19.54PCh. 19 - Prob. 19.55PCh. 19 - Prob. 19.56PCh. 19 - Prob. 19.57PCh. 19 - Prob. 19.58PCh. 19 - Prob. 19.59PCh. 19 - Prob. 19.60PCh. 19 - Prob. 19.61PCh. 19 - Use figure 19.9 to find an indicator for these...Ch. 19 - Prob. 19.63PCh. 19 - Prob. 19.64PCh. 19 - Prob. 19.65PCh. 19 - Prob. 19.66PCh. 19 - Write the ion-product expressions for (a) silver...Ch. 19 - Write the ion-product expressions for (a)...Ch. 19 - Write the ion-product expressions for (a) calcium...Ch. 19 - Prob. 19.70PCh. 19 - The solubility of silver carbonate is 0.032 M at...Ch. 19 - Prob. 19.72PCh. 19 - Prob. 19.73PCh. 19 - The solubility of calcium sulfate at 30°C is 0.209...Ch. 19 - Prob. 19.75PCh. 19 - Prob. 19.76PCh. 19 - Prob. 19.77PCh. 19 - Calculate the molar solubility of Ag2SO4 in (a)...Ch. 19 - Prob. 19.79PCh. 19 - Prob. 19.80PCh. 19 - Prob. 19.81PCh. 19 - Prob. 19.82PCh. 19 - Prob. 19.83PCh. 19 - Write equations to show whether the solubility of...Ch. 19 - Prob. 19.85PCh. 19 - Prob. 19.86PCh. 19 - Prob. 19.87PCh. 19 - Does any solid PbCl2 form when 3.5 mg of NaCl is...Ch. 19 - Prob. 19.89PCh. 19 - Prob. 19.90PCh. 19 - Prob. 19.91PCh. 19 - A 50.0-mL volume of 0.50 M Fe(NO3)3 is mixed with...Ch. 19 - Prob. 19.93PCh. 19 - Prob. 19.94PCh. 19 - Prob. 19.95PCh. 19 - Write a balanced equation for the reaction of in...Ch. 19 - Prob. 19.97PCh. 19 - Prob. 19.98PCh. 19 - Prob. 19.99PCh. 19 - What is [Ag+] when 25.0 mL each of 0.044 M AgNO3...Ch. 19 - Prob. 19.101PCh. 19 - Prob. 19.102PCh. 19 - Prob. 19.103PCh. 19 - When 0.84 g of ZnCl2 is dissolved in 245 mL of...Ch. 19 - When 2.4 g of Co(NO3)2 is dissolved in 0.350 L of...Ch. 19 - Prob. 19.106PCh. 19 - A microbiologist is preparing a medium on which to...Ch. 19 - As an FDA physiologist, you need 0.700 L of formic...Ch. 19 - Tris(hydroxymethyl)aminomethane [(HOCH2)3CNH2],...Ch. 19 - Water flowing through pipes of carbon steel must...Ch. 19 - Gout is caused by an error in metabolism that...Ch. 19 - In the process of cave formation (Section 19.3),...Ch. 19 - Phosphate systems form essential buffers in...Ch. 19 - The solubility of KCl is 3.7 M at 20°C. Two...Ch. 19 - It is possible to detect NH3 gas over 10−2 M NH3....Ch. 19 - Manganese(II) sulfide is one of the compounds...Ch. 19 - The normal pH of blood is 7.40 ± 0.05 and is...Ch. 19 - A bioengineer preparing cells for cloning bathes a...Ch. 19 - Sketch a qualitative curve for the titration of...Ch. 19 - Prob. 19.120PCh. 19 - The scene at right depicts a saturated solution of...Ch. 19 - Prob. 19.122PCh. 19 - The acid-base indicator ethyl orange turns from...Ch. 19 - Prob. 19.124PCh. 19 - Prob. 19.125PCh. 19 - Prob. 19.126PCh. 19 - Prob. 19.127PCh. 19 - Prob. 19.128PCh. 19 - Prob. 19.129PCh. 19 - Calcium ion present in water supplies is easily...Ch. 19 - Calculate the molar solubility of Hg2C2O4 (Ksp =...Ch. 19 - Environmental engineers use alkalinity as a...Ch. 19 - Human blood contains one buffer system based on...Ch. 19 - Quantitative analysis of Cl− ion is often...Ch. 19 - An ecobotanist separates the components of a...Ch. 19 - Some kidney stones form by the precipitation of...Ch. 19 - Prob. 19.137PCh. 19 - Prob. 19.138PCh. 19 - Because of the toxicity of mercury compounds,...Ch. 19 - A 35.0-mL solution of 0.075 M CaCl2 is mixed with...Ch. 19 - Rainwater is slightly acidic due to dissolved CO2....Ch. 19 - Prob. 19.142PCh. 19 - Ethylenediaminetetraacetic acid (abbreviated...Ch. 19 - Buffers that are based on...Ch. 19 - NaCl is purified by adding HCl to a saturated...Ch. 19 - Scenes A to D represent tiny portions of 0.10 M...Ch. 19 - Prob. 19.147PCh. 19 - Prob. 19.148PCh. 19 - Prob. 19.149P
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