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Questions and Answers
According to the Arrhenius theory, what is the defining characteristic of an acid?
According to the Arrhenius theory, what is the defining characteristic of an acid?
- It increases the concentration of $OH^-$ ions in water.
- It accepts a proton in aqueous solution.
- It donates a proton in aqueous solution.
- It increases the concentration of $H^+$ ions in water. (correct)
Which of the following compounds is classified as an Arrhenius base?
Which of the following compounds is classified as an Arrhenius base?
- $H_2SO_4$
- $HCl$
- $NaOH$ (correct)
- $CH_3COOH$
In the Bronsted-Lowry definition, what distinguishes a base from an acid?
In the Bronsted-Lowry definition, what distinguishes a base from an acid?
- A base decreases $H^+$ concentration, while an acid decreases $OH^-$ concentration.
- A base donates hydroxide ions, while an acid donates hydrogen ions.
- A base accepts protons, while an acid donates protons. (correct)
- A base increases $H^+$ concentration, while an acid increases $OH^-$ concentration.
Which of the following is true regarding Bronsted-Lowry acids and bases?
Which of the following is true regarding Bronsted-Lowry acids and bases?
What is the role of water in the reaction $HCl(g) + H_2O(l) \rightarrow H_3O^+(aq) + Cl^-(aq)$ according to the Bronsted-Lowry theory?
What is the role of water in the reaction $HCl(g) + H_2O(l) \rightarrow H_3O^+(aq) + Cl^-(aq)$ according to the Bronsted-Lowry theory?
Which of the following characteristics is essential for a molecule or ion to act as a Bronsted-Lowry base?
Which of the following characteristics is essential for a molecule or ion to act as a Bronsted-Lowry base?
In the reaction $NH_3(aq) + H_2O(l) \rightleftharpoons NH_4^+(aq) + OH^-(aq)$, which species is the Bronsted-Lowry acid?
In the reaction $NH_3(aq) + H_2O(l) \rightleftharpoons NH_4^+(aq) + OH^-(aq)$, which species is the Bronsted-Lowry acid?
What is the conjugate base of $H_2CO_3$?
What is the conjugate base of $H_2CO_3$?
Which of the following pairs represents a conjugate acid-base pair?
Which of the following pairs represents a conjugate acid-base pair?
What is the conjugate acid of $SO_4^{2-}$?
What is the conjugate acid of $SO_4^{2-}$?
If $HX$ is a weak acid, what does this imply about its conjugate base, $X^-$?
If $HX$ is a weak acid, what does this imply about its conjugate base, $X^-$?
Which of the following statements is true regarding conjugate acid-base pairs?
Which of the following statements is true regarding conjugate acid-base pairs?
In the reaction $HSO_3^-(aq) + H_2O(l) \rightleftharpoons SO_3^{2-}(aq) + H_3O^+(aq)$, what role does $HSO_3^-$ play?
In the reaction $HSO_3^-(aq) + H_2O(l) \rightleftharpoons SO_3^{2-}(aq) + H_3O^+(aq)$, what role does $HSO_3^-$ play?
Given the reaction: $HSO_4^-(aq) + CO_3^{2-}(aq) \rightleftharpoons SO_4^{2-}(aq) + HCO_3^-(aq)$. According to the relative strengths of acids and bases, which side of the equilibrium is favored?
Given the reaction: $HSO_4^-(aq) + CO_3^{2-}(aq) \rightleftharpoons SO_4^{2-}(aq) + HCO_3^-(aq)$. According to the relative strengths of acids and bases, which side of the equilibrium is favored?
Which of the following is the stronger acid?
Which of the following is the stronger acid?
In the equilibrium reaction $HSO_4^-(aq) + CO_3^{2-}(aq) \rightleftharpoons SO_4^{2-}(aq) + HCO_3^-(aq)$, which species is the stronger base?
In the equilibrium reaction $HSO_4^-(aq) + CO_3^{2-}(aq) \rightleftharpoons SO_4^{2-}(aq) + HCO_3^-(aq)$, which species is the stronger base?
Which of the following is the conjugate base of $H_2O$?
Which of the following is the conjugate base of $H_2O$?
What is the conjugate acid of $OH^-$?
What is the conjugate acid of $OH^-$?
Based on relative strengths, which of the following bases is the weakest?
Based on relative strengths, which of the following bases is the weakest?
Based on relative strengths, which of the following acids is the strongest?
Based on relative strengths, which of the following acids is the strongest?
Flashcards
Arrhenius Acid
Arrhenius Acid
A substance that increases the concentration of H+ ions when dissolved in water.
Arrhenius Base
Arrhenius Base
A substance that increases the concentration of OH- ions when dissolved in water.
Brønsted-Lowry Acid
Brønsted-Lowry Acid
A substance that donates a proton (H+) to another substance.
Brønsted-Lowry Base
Brønsted-Lowry Base
A substance that accepts a proton (H+).
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Proton Transfer
Proton Transfer
An acid-base reaction involving the transfer of H+ ions from one substance to another.
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Conjugate Base
Conjugate Base
The molecule or ion remaining after an acid loses a proton.
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Conjugate Acid
Conjugate Acid
The molecule or ion remaining after a base gains a proton.
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Conjugate Acid-Base Pairs
Conjugate Acid-Base Pairs
Acids and bases that differ only by the presence or absence of a proton.
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Conjugate Base Formation
Conjugate Base Formation
Formed by removing a proton (H+) from an acid.
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Conjugate Acid Formation
Conjugate Acid Formation
Formed by adding a proton (H+) to a base.
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Amphiprotic Substances
Amphiprotic Substances
These molecules may act as a Brønsted-Lowry acid or base, depending on the reaction conditions.
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Relative Strengths
Relative Strengths
The stronger the acid, the weaker its conjugate base; the stronger the base, the weaker its conjugate acid.
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Equilibrium Position
Equilibrium Position
In acid-base equilibria, equilibrium favors transfer to form the weaker acid and weaker base.
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Arrhenius Theory of Acids and Bases
- An acid increases the concentration of H+ ions when dissolved in water.
- A base increases the concentration of OH- ions when dissolved in water.
- Hydrochloric acid (HCl) is an Arrhenius acid, producing hydrated H+ and Cl- ions when added to water.
- Sodium hydroxide (NaOH) is an Arrhenius base because it dissociates into Na+ and OH- ions in water, releasing hydroxide ions.
Brønsted-Lowry Theory of Acids and Bases
- Acid-base reactions involve the transfer of H+ ions (protons) from one substance to another.
- The addition of HCl to water involves the HCl molecule transferring a proton to a water molecule, forming hydronium (H3O+) and chloride ions.
- A Brønsted acid is a substance (molecule or ion) that donates a proton to another substance.
- A Brønsted base is a substance that accepts a proton.
- The gas phase reaction between HCl and NH3, shows this proton transfer.
- Ammonia (NH3) is a Brønsted-Lowry base because it accepts a proton from water.
- Ammonia is also an Arrhenius base because adding it to water increases the concentration of OH- ions.
- To be a Brønsted-Lowry base, a molecule or ion must have a non-bonding pair of electrons that it can use to bind to the H+ ion.
Conjugate Acid-Base Pairs
- In any acid-base equilibrium, both the forward and reverse reactions involve proton transfer.
- In a forward reaction, HX acts as a Brønsted-Lowry acid (proton donor), while water acts as a Brønsted-Lowry base (proton acceptor).
- In the reverse reaction, H3O+ acts as an acid (proton donor), and X- acts as a base (proton acceptor).
- Acids and bases, such as HA and A-, that differ only in the presence or absence of a proton are called conjugate acid-base pairs.
- Every acid has a conjugate base, formed by removing a proton.
- Every base has a conjugate acid, formed by adding a proton.
Exercises
- Every acid has a conjugate base formed by removing a proton from the acid.
- The conjugate base of perchloric acid (HClO4) is perchlorate (ClO4-).
- The conjugate base of hydrogen sulfide (H2S) is hydrosulfide (HS-).
- The conjugate base of ammonium (PH4+) is phosphine (PH3).
- The conjugate base of bicarbonate (HCO3-) is carbonate (CO32-).
- Every base has a conjugate acid formed by adding a proton.
- The conjugate acid of cyanide (CN-) is hydrocyanic acid (HCN).
- The conjugate acid of sulfate (SO42-) is bisulfate (HSO4-).
- The conjugate acid of water (H2O) is hydronium (H3O+).
- The conjugate acid of bicarbonate (HCO3-) is carbonic acid (H2CO3).
- Every acid has a conjugate base is formed by removing a proton is applicable to the reaction of HSO3- with water.
- Every base has a conjugate acid, formed by adding a proton to the base for both parts a and b with hydrogen sulphite.
Relative Strengths of Acids and Bases
- The stronger the acid, the weaker its conjugate base, and the stronger the base, the weaker its conjugate acid.
- In the example of the equilibrium between HSO4- and CO32-, HSO4- is the stronger acid and is more likely to deprotonate than the conjugate acid (HCO3-), which favors an equilibrium.
- The base (CO32-) is also stronger, thus equilibrium favors an equilibrium shift, meaning that this base is more likely to gain a proton than its conjugate base.
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