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WorksheetsCh 18 Aqueous Ionic Equilibrium
Total questions: 74
Worksheet time: 37mins
What is a buffer?
A solution that resists changes in pH when small amounts of acid or base are added.
A substance that increases the rate of a chemical reaction.
A compound that completely dissociates in water.
A solution that only contains water and salt.
What is solubility equilibria?
The state where the rate of dissolution and precipitation of a solute are equal in a solution.
The process of dissolving a solute in a solvent.
The point at which a solution becomes supersaturated.
The temperature at which a solute dissolves fastest.
Why are buffers important in Biology?
They help maintain a stable pH in biological systems.
They speed up metabolic reactions.
They provide energy for cells.
They act as enzymes in the body.
What deviation from our solubility rules do we encounter?
Some compounds that should be soluble are actually insoluble under certain conditions.
All compounds always follow the solubility rules.
No compounds deviate from the solubility rules.
Solubility rules only apply to gases.
What specific problem can the ingestion of antifreeze cause chemically in the body?
It leads to the formation of toxic metabolites that can cause organ damage.
It increases the oxygen-carrying capacity of blood.
It neutralizes stomach acid.
It causes rapid cell division.
What is the pH range of human blood?
7.35 to 7.45
6.0 to 6.5
8.0 to 8.5
5.5 to 6.0
Describe the Carbonic acid/bicarbonate buffer system:
It maintains blood pH by balancing carbonic acid and bicarbonate ions.
It increases the acidity of the stomach.
It removes all carbon dioxide from the blood.
It only works in the digestive system.
Define acidosis.
A condition where the blood pH drops below the normal range.
A condition where the blood pH rises above the normal range.
A state of complete hydration.
A process of breaking down proteins.
What is the cure for antifreeze poisoning and how does it work?
Administering ethanol or fomepizole, which inhibits the enzyme that metabolizes antifreeze into toxic compounds.
Giving the patient more water to dilute the antifreeze.
Inducing vomiting to remove antifreeze from the stomach.
Providing oxygen therapy to the patient.
Buffers are solutions that resist changes in what property?
Temperature
pH
Volume
Pressure
What do buffers typically contain?
Only a strong acid
Only a strong base
A weak acid and its conjugate base
Water and salt only
The primary buffer in blood is composed of which acid and its conjugate base?
Hydrochloric acid and chloride
Carbonic acid and bicarbonate
Acetic acid and acetate
Sulfuric acid and sulfate
Which of the following best describes how a buffer works?
It neutralizes all acids and bases completely.
It maintains a constant temperature.
It reacts with added acids or bases to minimize pH changes.
It increases the pH of a solution.
If a strong base is added to an acetic acid/sodium acetate buffer, what will happen?
The pH will increase drastically.
The buffer will neutralize the base, minimizing pH change.
The buffer will become acidic.
The solution will evaporate.
How does an acetic acid/sodium acetate buffer respond to the addition of a strong acid?
The pH will drop sharply.
The buffer will neutralize the acid, minimizing pH change.
The buffer will become basic.
The solution will freeze.
Which of the following summarizes the characteristics of a buffer?
Buffers only work with strong acids and bases.
Buffers are solutions that resist changes in pH when small amounts of acid or base are added.
Buffers increase the pH of any solution.
Buffers are only found in laboratory settings.
Describe the Henderson-Hasselbalch Equation and how is it used in buffer calculations:
It relates the pH of a solution to the concentration of acid and its conjugate base, and is used to calculate the pH of buffer solutions.
It is used to determine the boiling point of a solution.
It calculates the solubility of salts in water.
It measures the rate of a chemical reaction.
Derive the expression for the hydronium ion:
[H₃O⁺] = Ka × ([HA]/[A⁻])
[H₃O⁺] = Kw / [OH⁻]
[H₃O⁺] = pKa + log([A⁻]/[HA])
[H₃O⁺] = [Na⁺] × [Cl⁻]
How does the “x is small” approximation impact weak acid or weak base problems?
It allows for the simplification of calculations by assuming the change in concentration is negligible.
It increases the accuracy of the calculation.
It is used to determine the boiling point of acids.
It is only applicable to strong acids and bases.
Write the Henderson-Hasselbalch equation:
pH = pKa + log([A⁻]/[HA])
pH = -log[H⁺]
pH = pKw - pOH
pH = log([HA]/[A⁻])
What are the two ways to calculate pH changes in Buffer Solutions?
Using the Henderson-Hasselbalch equation and by direct calculation from acid/base concentrations.
By measuring temperature and pressure.
By using a colorimeter and a thermometer.
By titrating with a strong acid only.
Which of the following is a key topic mentioned in the material for Practice 18.2?
Calculating pH changes in a buffer solution
Balancing chemical equations
Determining molar mass
Identifying types of chemical bonds
What are students asked to describe in Conceptual Connection 18.2?
The two methods for calculating pH changes in a buffer solution
The process of titration
The properties of acids and bases
The steps for preparing a buffer solution
How might a student decide which method to use for calculating pH changes in practice, homework, labs, and tests?
By considering the context and requirements of the task
By always using the same method regardless of the situation
By choosing the method that takes the least time
By randomly selecting a method
Which of the following is an example of a buffer containing a base and its conjugate acid?
Ammonia (NH₃) and ammonium chloride (NH₄Cl)
Hydrochloric acid (HCl) and sodium chloride (NaCl)
Sulfuric acid (H₂SO₄) and sodium sulfate (Na₂SO₄)
Sodium hydroxide (NaOH) and sodium chloride (NaCl)
How is the pH of a buffer system containing a base and its conjugate acid typically calculated?
By using the Henderson-Hasselbalch equation
By measuring the temperature of the solution
By adding the concentrations of acid and base
By using the molar mass of the base
What is an effective buffer?
A solution that resists changes in pH when small amounts of acid or base are added.
A solution that increases pH rapidly.
A solution that only contains water.
A solution that cannot resist any pH change.
What factors influence the effectiveness of a buffer?
The concentration of the buffer components and the ratio of acid to base.
The color of the solution.
The temperature of the room only.
The size of the container.
Describe the capacity of a buffer.
The amount of acid or base the buffer can neutralize before the pH changes significantly.
The speed at which the buffer changes color.
The temperature at which the buffer boils.
The volume of the buffer solution.
Describe the range of a buffer.
The pH range over which the buffer is effective.
The distance the buffer can travel.
The time the buffer lasts.
The number of ions in the buffer.
When is a buffer most effective?
When the concentration of acid and base are nearly equal.
When the buffer is diluted.
When the buffer is heated.
When the buffer is frozen.
How is the buffering range selected?
By choosing a buffer with a pKa close to the desired pH.
By choosing the buffer with the brightest color.
By selecting the buffer with the largest volume.
By picking the buffer with the highest boiling point.
How does dilution affect buffer effectiveness?
It increases buffer effectiveness
It decreases buffer effectiveness
It has no effect on buffer effectiveness
It changes the pH of the buffer
Describe how to calculate the most effective buffering range.
By using the sum of acid and base concentrations
By using the pKa value of the acid and adjusting pH within ±1 of the pKa
By measuring the temperature of the solution
By adding more water to the buffer
What is a rule of thumb when deciding the effective range of a buffer system?
The effective range is always at pH 7
The effective range is within ±1 pH unit of the acid’s pKa
The effective range is determined by the color of the solution
The effective range is only at high concentrations
Describe the buffering in human blood.
Human blood is buffered by sodium chloride
Human blood is buffered by the carbonic acid-bicarbonate system
Human blood is not buffered
Human blood is buffered by proteins only
What is buffer capacity?
The ability of a solution to resist changes in pH when an acid or base is added
The amount of acid in a solution
The temperature at which a buffer works best
The color change of a solution
Which of the following is a primary characteristic of buffer capacity?
It depends on the concentration of the buffer components
It is independent of the amount of acid or base added
It only works at high temperatures
It is unrelated to pH
What is an acid-base titration?
A process to determine the concentration of an acid or base by reacting it with a base or acid of known concentration
A method to measure temperature changes in a solution
A way to separate mixtures
A process to evaporate water from a solution
How are titrations typically monitored?
By observing a color change with an indicator
By measuring the mass of the solution
By heating the solution
By freezing the solution
What is the equivalence point in a titration?
The point at which the amount of acid equals the amount of base
The point at which the solution changes color
The point at which the solution is heated
The point at which the solution is diluted
Which statement best describes a titration or pH curve?
A graph showing the change in pH as a function of the volume of titrant added
A chart of temperature versus time
A diagram of molecular structures
A list of chemical elements
What calculation is necessary to begin the titration of a strong acid with a strong base?
Determining the initial concentration of the acid
Calculating the boiling point of the acid
Measuring the temperature of the solution
Finding the color of the indicator
What calculations are necessary as you proceed with the titration of a strong acid with a strong base?
Calculating the pH after each addition of base
Measuring the mass of the beaker
Determining the melting point of the base
Calculating the density of the acid
Theoretically, when is the equivalence point reached during the titration of a strong acid with a strong base?
When the amount of acid equals the amount of base
When the solution changes color
When the temperature reaches 100°C
When the solution becomes cloudy
Describe what accommodations must be made to calculations after each subsequent addition of strong base during titration.
Adjusting the volume and concentration of both acid and base
Ignoring the changes in volume
Only measuring the temperature
Calculating the mass of the indicator
How is titrating a strong base with a strong acid different or the same as titrating a strong acid with a strong base?
The process is essentially the same, but the roles of acid and base are reversed
The process uses a different indicator
The process requires a different type of glassware
The process is not possible
How does titrating a weak base with a strong acid differ from titrating a weak acid with a strong base in terms of the curve and calculations?
The titration curve for a weak base with a strong acid starts at a higher pH and ends at a lower pH, while the reverse is true for a weak acid with a strong base.
Both titration curves are identical in shape and calculations.
The titration of a weak base with a strong acid does not involve any buffer region.
The calculations for both titrations do not require the use of equilibrium constants.
What is unique about titrating a polyprotic acid?
It has multiple equivalence points due to the presence of more than one ionizable proton.
It only has one equivalence point.
The pH remains constant throughout the titration.
Polyprotic acids cannot be titrated.
Explain significant points in the titration curve of a polyprotic acid.
There are multiple buffer regions and equivalence points corresponding to each ionizable proton.
There is only one significant point at the start of the titration.
The curve is a straight line with no significant points.
The titration curve does not show any buffer regions.
Which of the following best defines a substance that is "soluble"?
A substance that dissolves in a solvent to a significant extent
A substance that does not dissolve in any solvent
A substance that reacts with acids only
A substance that evaporates quickly
What does the term "insoluble" refer to?
A substance that dissolves completely in water
A substance that does not dissolve appreciably in a solvent
A substance that changes color in acid
A substance that conducts electricity
What is Ksp in the context of solubility equilibria?
The equilibrium constant for the dissolution of a sparingly soluble compound
The boiling point of a solution
The rate at which a solute dissolves
The pH at which a solution is neutral
Which of the following best defines "molar solubility"?
The number of moles of solute that can dissolve per liter of solution
The mass of solute that can dissolve in 100 mL of water
The temperature at which a solute dissolves
The pressure required to dissolve a gas in a liquid
How do Ksp and molar solubility differ from one another?
Ksp is a constant for a given compound at a specific temperature, while molar solubility is the amount of solute that dissolves to form a saturated solution.
Ksp measures the rate of dissolution, while molar solubility measures the color change.
Ksp is only used for gases, while molar solubility is used for solids.
Ksp and molar solubility are identical and interchangeable.
Why is water considered hard?
Because it contains high concentrations of dissolved minerals such as calcium and magnesium.
Because it is frozen.
Because it is at a high temperature.
Because it is pure and free of minerals.
What can one do to ‘soften’ water?
Remove calcium and magnesium ions from the water.
Add more minerals to the water.
Boil the water.
Freeze the water.
What are the risks associated with softening water?
Softened water may have higher sodium content, which can be a concern for people on low-sodium diets.
Softened water can cause pipes to freeze.
Softened water is more likely to evaporate quickly.
Softened water can turn into hard water again.
Can Ksp values of two different compounds be used to compare relative solubilities? Explain.
No, because the stoichiometry of dissociation must also be considered.
Yes, Ksp values alone are always sufficient.
No, Ksp values are unrelated to solubility.
Yes, but only if the compounds are gases.
What is dissociation stoichiometry?
The ratio in which a compound breaks apart into its ions in solution.
The process of heating a compound.
The method of filtering a solution.
The way a compound is synthesized.
What is the effect of a common ion on the solubility of a salt in solution?
It increases the solubility of the salt.
It decreases the solubility of the salt.
It has no effect on the solubility of the salt.
It changes the color of the solution.
Which of the following best describes the effect of pH on the solubility of a salt containing a basic anion?
Increasing pH increases solubility.
Decreasing pH increases solubility.
pH has no effect on solubility.
Solubility decreases as pH decreases.
A solution contains a salt and a common ion. What reasoning explains why the solubility of the salt decreases?
The common ion reacts with the salt to form a new compound.
The presence of the common ion shifts the dissolution equilibrium to favor the solid form.
The common ion increases the temperature of the solution.
The common ion increases the pressure in the solution.
How does a precipitate form?
When two solutions are mixed and an insoluble solid forms
When a gas is released from a solution
When a solution evaporates completely
When a liquid is heated to boiling
How has the concept of solubility changed since Chapter 5?
It now includes the effect of temperature and pressure on solubility
It only considers the solubility of gases
It ignores the role of ionic compounds
It focuses solely on organic compounds
How is Q related to solubility?
Q compares the current ion product to the solubility product constant (Ksp)
Q measures the temperature of a solution
Q is unrelated to solubility
Q is the concentration of water in a solution
How can Q and Ksp be related to view ionic compounds in solution (discuss 3 relationships)?
Q < Ksp (unsaturated), Q = Ksp (saturated), Q > Ksp (supersaturated/precipitate forms)
Q = Ksp only (no other relationships)
Q and Ksp are unrelated
Q is always greater than Ksp
Summarize the Relationship of Q and Ksp in Solutions Containing an Ionic Compound:
If Q < Ksp, no precipitate forms; if Q = Ksp, the solution is saturated; if Q > Ksp, a precipitate forms
If Q > Ksp, no precipitate forms
If Q = Ksp, the solution is unsaturated
Q and Ksp do not affect precipitation
What is the main difference between qualitative and quantitative analysis?
Qualitative analysis identifies the components present, while quantitative analysis measures the amount of each component.
Qualitative analysis measures the amount of each component, while quantitative analysis identifies the components present.
Both qualitative and quantitative analysis only identify components.
Both qualitative and quantitative analysis only measure amounts.
Why is a Qualitative Analysis Scheme important in chemical analysis?
It helps identify the presence of specific ions or compounds in a mixture.
It measures the exact mass of a compound.
It determines the boiling point of a substance.
It is used to calculate the pH of a solution.
Which of the following best describes insoluble and soluble groups in a Qualitative Analysis Scheme?
Insoluble groups do not dissolve in water, while soluble groups do.
Insoluble groups are always metals, while soluble groups are always nonmetals.
Insoluble groups are gases, while soluble groups are liquids.
Insoluble groups are organic, while soluble groups are inorganic.
What is a common tendency of transition metals?
They often form complex ions.
They are always colorless.
They do not react with water.
They are always gases at room temperature.
How does water typically interact with transition metal ions?
Water acts as a ligand and can coordinate to transition metal ions.
Water always decomposes transition metal ions.
Water prevents the formation of complex ions.
Water has no effect on transition metal ions.
Which statement best describes a complex ion?
A complex ion consists of a central metal ion bonded to one or more molecules or ions.
A complex ion is a simple ion with no attached molecules.
A complex ion is always negatively charged.
A complex ion is a molecule with only nonmetals.
