Acids, Bases, and Titrations Flashcards

Flashcards based on lecture notes about acids, bases, and titrations.

What does the Arrhenius model of acids state?

Acids release hydrogen ions (H+) into solution.

What does the Arrhenius model of bases state?

Bases release hydroxide ions (OH-) into solution.

Give examples of Arrhenius acids.

Hydrochloric acid (HCl), nitric acid (HNO3), and sulfuric acid (H2SO4).

Give examples of Arrhenius bases.

Sodium hydroxide (NaOH), calcium hydroxide (Ca(OH)2), and iron (III) hydroxide (Fe(OH)3).

What is a monoprotic acid?

An acid that releases only one hydrogen ion into solution.

Give examples of monoprotic acids.

Hydrochloric acid (HCl), nitric acid (HNO3), and acetic acid (CH3COOH).

What is a polyprotic acid?

An acid that releases more than one hydrogen ion into solution.

Give examples of polyprotic acids.

Sulfuric acid (H2SO4), phosphoric acid (H3PO4), and ethanedioic acid ((COOH)2).

What does the Bronsted-Lowry theory of acids state?

Acids are substances that donate protons to other substances.

What does the Bronsted-Lowry theory of bases state?

Bases are substances that accept protons from other substances.

Give examples of Bronsted-Lowry acids.

Hydrochloric acid (HCl), nitric acid (HNO3), water (H2O).

Give examples of Bronsted-Lowry bases.

Sodium hydroxide (NaOH), ammonia (NH3), sodium carbonate (Na2CO3), water (H2O).

According to Arrhenius, why is HCl an acid in the reaction HCl(aq) + NaOH(aq) à NaCl(aq) + H2O(l)?

Because it releases H+ in solution.

According to Arrhenius, why is NaOH a base in the reaction HCl(aq) + NaOH(aq) à NaCl(aq) + H2O(l)?

Because it releases OH- in solution.

According to Bronsted-Lowry, why is HCl an acid in the reaction HCl(aq) + NaOH(aq) à NaCl(aq) + H2O(l)?

Because it donates a proton to NaOH to produce water.

According to Bronsted-Lowry, why is NaOH a base in the reaction HCl(aq) + NaOH(aq) à NaCl(aq) + H2O(l)?

Because it accepts a proton from the HCl to produce water.

What does concentration refer to?

The quantity of solute dissolved in a set volume of solvent.

What does strength refer to in the context of solutions?

How well a solute dissociates in solution.

What is a strong electrolyte?

A solution where a majority of the solute has dissociated.

What is a weak electrolyte?

A solution where only a small amount of the solute has dissociated.

What is a non-electrolyte?

A solution with no solute dissolved in it.

Give examples of strong acids.

Hydrochloric acid, nitric acid, sulfuric acid.

Give examples of weak acids.

Hydrofluoric acid, acetic acid, oxalic acid.

Give examples of strong bases.

Sodium hydroxide, calcium hydroxide, potassium hydroxide.

Give examples of weak bases.

Ammonia, aluminum hydroxide, methylamine.

How can the acidity constant (Ka) be used to describe a strong acid?

A high Ka value indicates that the equilibrium position resides to the right, demonstrating the high dissociation of strong acids into their ions.

How can the acidity constant (Ka) be used to describe a weak acid?

A low Ka value indicates that the equilibrium position sits to the left, showing that the acid prefers to remain in its molecular form.

Describe the pH of a strong acid.

Strong acids liberate maximum hydrogen ions into solution, resulting in very low pH values.

Describe the pH of a weak acid.

Weak acids liberate few hydrogen ions in solution, resulting in a pH value below 7 but closer to 7.

What is a conjugate acid?

The product of a base in an acid-base reaction.

What is a conjugate base?

The product of an acid in an acid-base reaction.

What does a conjugate base originate from?

An acid.

What is a pH indicator?

A compound that undergoes a color change in solution over a specific range of pH values, revealing whether a solution is acidic, neutral, or alkaline.

What determines the color of a pH indicator?

The increase or decrease in [H3O+] (hydronium ion concentration).

What happens to the indicator in an acid?

The [H3O+] increases, the reverse reaction is favored, resulting in a reduction in [H3O+], which increases the production of HIn, and shows the acid color.

What happens to an indicator in a base?

The [H3O+] decreases, the forward reaction is favored, resulting in an increase in [H3O+], which increases the production of In-, and shows the base color.

What is the pH range and color transition of phenolphthalein?

pH Range: Approximately 8 to 10. Color Transition: Colorless to pink.

What is the pH range and color transition of methyl red?

pH Range: 4.4 and 6.2. Color Transition: Red below pH 4.4, yellow above pH 6.2, orange within the range.

What is the pH range and color transition of bromothymol blue?

pH Range: 6 and 7.5. Color Transition: Yellow to blue.

What solutions will produce an acidic salt?

The reaction of a strong acid and a weak base.

What solutions will produce a basic salt?

The reaction of a weak acid and a strong base.

What could be used to prepare a low pH buffer?

A weak acid and its salt (e.g., acetic acid and sodium acetate).

What could be used to prepare a high pH buffer?

A weak base and its salt (e.g., ammonia and ammonium chloride).

Outline the effect of adding acid to an acidic buffer.

The [H3O+] increases (and the pH decreases), the system counteracts the addition of H3O+ by increasing the rate of the reverse reaction relative to the forward reaction, which in turn, decreases [H3O+] and brings the pH back to where it began.

Outline the effect of adding base to an acid buffer.

The [H3O+] decreases (and the pH increases) as the OH- ions cause the production of water, the system counteracts the reduction of H3O+ by increasing the rate of the forward reaction relative to the reverse reaction, which in turn, increases [H3O+] and brings the pH back to where it began.

Outline the effect of adding acid to a basic buffer.

The [OH-] decreases (and the pH decreases) as H3O+ causes the formation of water, the system counteracts the reduction of OH- by increasing the rate of the forward reaction relative to the reverse reaction, which in turn, increases [OH-] and brings the pH back to where it began.

Outline the effect of adding base to a basic buffer.

The [OH-] increases (and the pH increases), the system counteracts the addition of OH- by increasing the rate of the reverse reaction relative to the forward reaction, which in turn, decreases [OH-] and brings the pH back to where it began.

Why is the bicarbonate buffer system important?

It is a crucial acid-base homeostatic mechanism that helps maintain the pH balance in the blood and other tissues.

What is the role of the respiratory system in the bicarbonate buffer system?

Helps regulate the levels of CO₂ by adjusting the rate and depth of breathing.

What is the role of the kidneys in the bicarbonate buffer system?

Help regulate the concentration of bicarbonate ions by reabsorbing HCO₃⁻ and secreting H⁺ into the urine.

Why is the phosphate buffer system important?

It is another important mechanism for maintaining pH balance in the body, particularly in the intracellular fluid and the kidneys.

Give some applications of buffer systems.

Biological systems, chemical reactions, analytical chemistry, and industrial processes.

What is volumetric analysis?

A set of analytical techniques (called titrations) that use volumes of reagents to determine concentration.

What is a primary standard?

A highly pure and stable chemical reagent used to prepare standard solutions.

What does non-hygroscopic mean?

Does not absorb moisture from the air.

Why must a primary standard have low reactivity?

To remain stable both in air and solution.

Why is sodium hydroxide not suitable as a primary standard?

It absorbs water and carbon dioxide from the air, affecting mass measurements.

What could compromise a secondary standard's accuracy?

Process (technique) errors.

Outline the process of preparing a standard solution.

1. Select an appropriate primary standard 2. Weigh the primary standard 3. Dissolve in solvent 4. Transfer to volumetric flask 5. Dilute to volume 6. Standardize the solution to get an accurate value for the secondary standard. 7. Label and store the solution

How can cleaning techniques create errors in titrations?

Inadequate cleaning can lead to dilution or contamination, affecting reagent concentrations.

How should analytical glassware be rinsed?

A pipette, burette, or storage bottle must first be washed with distilled water and then rinsed with a small amount of the solution that goes into it.

What errors can be caused by draining a pipette?

Applying pressure can cause a systematic error where the volume released is slightly greater than what it is supposed to be.

What can affect the determination of an endpoint?

A consistent approach is required to ensure the endpoint is determined the same way between titrations.

What is the 'equivalence point' in a titration?

The point where neither acid nor base remain, and the reaction is complete.

What is the 'end point' in a titration?

Occurs when one drop of titrant changes the color of the pH indicator.

How does the strength of an acid or base affect the equivalence point?

The strength of an acid or base affects equivalence point in the following ways: strong acid + strong base = equivalence point at pH 7. strong acid + weak base = equivalence point below pH 7. weak acid + strong base = equivalence point above pH 7. weak acid + weak base = equivalence point close to pH 7.

What is accuracy?

How close a value is to a true or measured value.

What is precision?

How close values are to each other.

What is systematic error?

A type of error where the values are either consistently higher or lower than the actual value (bias).

What is random error?

A type of error which causes inconsistent values (scatter).