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Questions and Answers
What characterizes Lewis acids?
What characterizes Lewis acids?
- They are always weak acids.
- They don’t accept lone pairs of electrons.
- They can only be organic compounds.
- They are electron-poor molecules or cations. (correct)
Why does an aqueous solution of FeCl3 turn out to be acidic?
Why does an aqueous solution of FeCl3 turn out to be acidic?
- Electron density flows towards the metal cation, weakening O-H bonds. (correct)
- The hydrogen atoms in water become negatively charged.
- It dissociates into FeCl2 and H2O.
- FeCl3 is a strong base in water.
What conclusion can be drawn about weak acids and their conjugate bases?
What conclusion can be drawn about weak acids and their conjugate bases?
- Weak acids have weaker conjugate bases compared to strong acids.
- The weaker the acid, the stronger its conjugate base. (correct)
- The stronger the acid, the stronger its conjugate base.
- Conjugate bases of weak acids are always strong acids.
How does the equilibrium lie for a strong acid like HCl in water?
How does the equilibrium lie for a strong acid like HCl in water?
What is the characteristic of a weak acid in terms of dissociation?
What is the characteristic of a weak acid in terms of dissociation?
What is the role of water in the dissociation reaction 2 H2O(l) H3O+(aq) + OH-(aq)?
What is the role of water in the dissociation reaction 2 H2O(l) H3O+(aq) + OH-(aq)?
Which of the following concentrations is correct for hydronium ions in pure distilled water at 25 oC?
Which of the following concentrations is correct for hydronium ions in pure distilled water at 25 oC?
What is the molarity of undissociated water in a liter of pure water?
What is the molarity of undissociated water in a liter of pure water?
What is the ion product constant for water (Kw) defined as?
What is the ion product constant for water (Kw) defined as?
In the reaction HCl(aq) + H2O(l) H3O+(aq) + Cl-(aq), what role does water play?
In the reaction HCl(aq) + H2O(l) H3O+(aq) + Cl-(aq), what role does water play?
According to Brönsted-Lowry theory, which of the following correctly describes a Brönsted-Lowry acid?
According to Brönsted-Lowry theory, which of the following correctly describes a Brönsted-Lowry acid?
What is the role of NH3 in the reaction where it interacts with H2O as described by Brönsted-Lowry theory?
What is the role of NH3 in the reaction where it interacts with H2O as described by Brönsted-Lowry theory?
Which pair represents a conjugate acid-base pair according to Brönsted-Lowry theory?
Which pair represents a conjugate acid-base pair according to Brönsted-Lowry theory?
What defines a Lewis acid?
What defines a Lewis acid?
In the context of Lewis acids and bases, what is the role of BF3 when reacting with NH3?
In the context of Lewis acids and bases, what is the role of BF3 when reacting with NH3?
Which of the following statements about the Brönsted-Lowry theory is correct?
Which of the following statements about the Brönsted-Lowry theory is correct?
What is a characteristic of a strong acid compared to a weak acid?
What is a characteristic of a strong acid compared to a weak acid?
Which of the following is true regarding the dissociation of distilled water?
Which of the following is true regarding the dissociation of distilled water?
What is the role of water in acid-base reactions according to the definitions provided?
What is the role of water in acid-base reactions according to the definitions provided?
Which of the following statements about acids and bases is true?
Which of the following statements about acids and bases is true?
How does the dissociation of strong acids differ from weak acids?
How does the dissociation of strong acids differ from weak acids?
What is the interpretation of Kw at 25°C?
What is the interpretation of Kw at 25°C?
Which method can be used to measure pH?
Which method can be used to measure pH?
What is the molarity of a solution containing 1000 g of a substance with a molar mass of 18.02 g/mol in 1.00 L?
What is the molarity of a solution containing 1000 g of a substance with a molar mass of 18.02 g/mol in 1.00 L?
At a temperature of 25 °C, what is the value of the ion-product constant, Kw?
At a temperature of 25 °C, what is the value of the ion-product constant, Kw?
How can pH be measured with high accuracy?
How can pH be measured with high accuracy?
What is the pH range that indicates a basic solution?
What is the pH range that indicates a basic solution?
Which statement is true regarding the use of methyl orange as an indicator?
Which statement is true regarding the use of methyl orange as an indicator?
What pH level is considered neutral?
What pH level is considered neutral?
What will a solution with a yellow color when tested with bromocresol purple indicate?
What will a solution with a yellow color when tested with bromocresol purple indicate?
What is the approximate pH of a solution that is yellow with both methyl orange and bromocresol purple?
What is the approximate pH of a solution that is yellow with both methyl orange and bromocresol purple?
What is the pH of a 0.050 M hydrochloric acid solution?
What is the pH of a 0.050 M hydrochloric acid solution?
Which formula is used to find the concentration of hydronium ions from hydroxide concentrations?
Which formula is used to find the concentration of hydronium ions from hydroxide concentrations?
What is the molarity of sodium hydroxide in a 100.0 mL solution made from dissolving 2.50 g of NaOH?
What is the molarity of sodium hydroxide in a 100.0 mL solution made from dissolving 2.50 g of NaOH?
Why do alkaline-earth metal hydroxides have lower pH values compared to alkali metal hydroxides, despite being strong bases?
Why do alkaline-earth metal hydroxides have lower pH values compared to alkali metal hydroxides, despite being strong bases?
If 5.00 g of Ca(OH)2 is dissolved in 1250.0 mL of solution, what is the pH of the resulting solution?
If 5.00 g of Ca(OH)2 is dissolved in 1250.0 mL of solution, what is the pH of the resulting solution?
How does the degree of dissociation of strong diprotic acids compare to strong monoprotic acids?
How does the degree of dissociation of strong diprotic acids compare to strong monoprotic acids?
What is the final pH of a solution where [H3O+] = 1.60 × 10^-14?
What is the final pH of a solution where [H3O+] = 1.60 × 10^-14?
What will happen to the pH if a strong acid is mixed with a strong base in equal concentrations?
What will happen to the pH if a strong acid is mixed with a strong base in equal concentrations?
Flashcards
Brønsted-Lowry Acid
Brønsted-Lowry Acid
A substance that can donate a proton (H+ ion) in a chemical reaction.
Brønsted-Lowry Base
Brønsted-Lowry Base
A substance that can accept a proton (H+ ion) in a chemical reaction.
Conjugate Base
Conjugate Base
A substance formed when an acid loses a proton. It can accept a proton to reform the acid.
Conjugate Acid
Conjugate Acid
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Lewis Acid
Lewis Acid
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Lewis Base
Lewis Base
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Proton Transfer Reaction
Proton Transfer Reaction
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Conjugate Acid-Base Pair
Conjugate Acid-Base Pair
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Nucleophiles
Nucleophiles
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Electrophiles
Electrophiles
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Weak Acid
Weak Acid
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What is Kw?
What is Kw?
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Amphoteric substance
Amphoteric substance
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Water as a base
Water as a base
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Water as an acid
Water as an acid
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What is the concentration of H3O+ in distilled water at 25°C?
What is the concentration of H3O+ in distilled water at 25°C?
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Arrhenius Acid
Arrhenius Acid
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Arrhenius Base
Arrhenius Base
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Ion-Product Constant (Kw)
Ion-Product Constant (Kw)
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pH Scale
pH Scale
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Acidic, Basic, and Neutral Solutions
Acidic, Basic, and Neutral Solutions
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pH Meter
pH Meter
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Acid-Base Indicators
Acid-Base Indicators
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Universal Indicator
Universal Indicator
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Buffer Solution
Buffer Solution
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Calibration of pH Meter
Calibration of pH Meter
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Strong Acid
Strong Acid
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pH of Strong Acids
pH of Strong Acids
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Strong Base
Strong Base
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pH of Strong Bases
pH of Strong Bases
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Solubility of Strong Bases
Solubility of Strong Bases
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Metal Oxides as Bases
Metal Oxides as Bases
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Strong Bases and Solubility
Strong Bases and Solubility
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Calculating pH of Strong Acids and Bases
Calculating pH of Strong Acids and Bases
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Study Notes
Acids and Bases 1
- Two definitions of acids and bases are examined: Brønsted-Lowry and Lewis.
- Brønsted-Lowry theory defines an acid as a proton (H⁺) donor and a base as a proton acceptor.
- An example of a Brønsted-Lowry acid-base reaction is shown with water and ammonia.
- In this reaction, water acts as an acid and ammonia acts as a base.
- Another example of a Brønsted-Lowry reaction is given with sulphuric acid and water.
- The Brønsted-Lowry theory has a disadvantage: it doesn't explain highly acidic solutions resulting from substances that aren't proton donors, such as FeCl₃.
- Lewis theory defines a Lewis acid as a lone pair acceptor and a Lewis base as a lone pair donor.
- An example illustrates a Lewis acid-base reaction where ammonia donates a lone pair to boron trifluoride.
- Another example shows the reaction between hydroxide and hydrogen chloride, where hydroxide acts as a Lewis base and hydrogen chloride acts as a Lewis acid.
- Lewis definitions are more comprehensive than previous definitions of acids and bases.
- These definitions are widely used in organic chemistry.
- Aqueous solutions of FeCl₃ are acidic because the hydrogen atoms in water are attracted to the metal cation, weakening their bonds with oxygen, which can then be abstracted by water molecules to form more H₃O⁺ ions.
Brønsted-Lowry Theory - Revision Slide
- In the Brønsted-Lowry theory example, H₂O donates a proton (H⁺ ion) to NH₃, making water a Brønsted-Lowry acid.
- In turn, NH₃ accepts a proton, making it a Brønsted-Lowry base.
- The reverse reaction shows a conjugate acid-base pair. NH₄⁺ donates a proton (H⁺ ion) to hydroxide (OH⁻), making NH₄⁺ a Brønsted-Lowry acid and OH⁻ a Brønsted-Lowry base.
- In summary, conjugate acid-base pairs are formed by an acid and a base in an equilibrium reaction.
Strong and Weak Acids
- A strong acid dissociates completely in water.
- The equilibrium lies to the right for strong acids.
- Strong acids have a very large equilibrium constant (HCl, for example).
- The conjugate base of a strong acid is very weak.
Weak Acids
- Weak acids dissociate only partially in water.
- The equilibrium for weak acids lies towards the left.
- Weak acids have a very small equilibrium constant, for example acetic acid.
- The conjugate base of weak acids is relatively strong.
Strengths of Acids and Their Conjugate Bases
- A table displays the relative strengths of various acids and their conjugate bases.
- The table is ordered from strong acids to weak acids.
- The stronger the acid, the weaker its conjugate base.
- The weaker the acid, the stronger its conjugate base.
Dissociation of Water
- Water is amphoteric, acting as both an acid and a base.
- Water as a base accepts protons (H⁺ ions), for example, when reacting with hydrochloric acid.
- Water as an acid donates protons (H⁺ ions), for example, when reacting with ammonia.
- A reaction between two water molecules illustrates how one water molecule acts as an acid and the other acts as a base, forming hydronium (H₃O⁺) and hydroxide (OH⁻) ions.
Water Dissociation
- Distilled water is a weak electrolyte.
- The concentration of hydronium ions ([H₃O⁺]) and hydroxide ions ([OH⁻]) in distilled water at 25 °C is 1.0 × 10⁻⁷ M.
- Two molecules in a billion dissociate.
Ion-Product Constant
- The ion-product constant (Kw) of water is a measure of the equilibrium between water molecules, hydronium (H₃O⁺) and hydroxide (OH⁻).
- Kw = [H₃O⁺][OH⁻] = 1.0 × 10⁻¹⁴ at 25ºC
- The concentrations of [H₃O⁺] and [OH⁻] in pure water are equal, making it neutral.
- Solutions with greater [H₃O⁺] than [OH⁻] are acidic, and basic solutions have a higher [OH⁻] concentration than [H₃O⁺].
The pH Scale
- pH is a measure of the acidity or basicity of a solution.
- pH = -log[H₃O⁺]
- Acidic solutions have pH values less than 7.
- Neutral solutions have a pH of 7.
- Basic solutions have pH values greater than 7.
- Values for pH can be negative or greater than 14, which depends on temperature.
pH of Some Common Substances
- A chart shows the pH values of common substances.
Measuring pH
- pH can be measured using an electronic meter, which is highly accurate.
- The electronic meter requires calibration with solutions of known pH like distilled water or buffer solutions.
- Acid-base indicators can also approximate pH.
- Universal indicators (paper strips or liquid) are another way to measure pH, offering relatively less precise measurements compared to the electronic meter.
pH for Strong Acids
- Strong monoprotic acids dissociate completely in water.
- Use the initial concentration of the strong acid to calculate [H₃O⁺], which is used to determine pH.
pH for Strong Bases
- Alkali metal hydroxides (MOH) dissociate almost completely in water, producing metal cations (M⁺) and hydroxide anions (OH⁻) in a 1:1 molar ratio.
- The concentration of hydroxide ions ([OH⁻]) can be used to calculate [H₃O⁺] and then pH.
Strong Bases (continued)
- Some alkaline-earth metal hydroxides, while being strong bases, do not completely dissociate; this results in fewer hydroxide ions, impacting their pH to become lower.
- Metal oxides like CaO react with water to form alkaline solutions.
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