What Is A Bronsted Base

88 Brønsted-Lowry Acids and Bases

Learning Objectives

1. Identify a Brønsted-Lowry acrid and a Brønsted-Lowry base of operations.
2. Identify conjugate acid-base of operations pairs in an acid-base reaction.

The Arrhenius definition of acid and base is limited to aqueous (that is, water) solutions. Although this is useful because water is a common solvent, information technology is limited to the relationship betwixt the H⁺ ion and the OH⁻ ion. What would be useful is a more full general definition that would be more applicable to other chemical reactions and, importantly, independent of H₂O.

In 1923, Danish pharmacist Johannes Brønsted and English language chemist Thomas Lowry independently proposed new definitions for acids and bases, ones that focus on proton transfer. A Brønsted-Lowry acid is whatever species that tin can donate a proton (H⁺) to another molecule. A Brønsted-Lowry base is any species that tin can accept a proton from another molecule. In brusque, a Brønsted-Lowry acid is a proton donor (PD), while a Brønsted-Lowry base of operations is a proton acceptor (PA).

Information technology is easy to run across that the Brønsted-Lowry definition covers the Arrhenius definition of acids and bases. Consider the prototypical Arrhenius acrid-base of operations reaction:

H⁺(aq)  + OH⁻(aq) → H_iiO(ℓ)

(acid)       (base)

The acid species and base species are marked. The proton, nevertheless, is (by definition) a proton donor (labelled PD), while the OH⁻ ion is acting as the proton acceptor (labelled PA):

H⁺(aq) + OH⁻(aq)→ H_twoO(ℓ)

(PD)          (PA)

The proton donor is a Brønsted-Lowry acrid, and the proton acceptor is the Brønsted-Lowry base of operations:

H⁺(aq)    +   OH⁻(aq) →  H₂O(ℓ)

(BL acid)    (BL base)

Thus H⁺ is an acid by both definitions, and OH⁻ is a base by both definitions.

Ammonia (NH_iii) is a base of operations even though it does not contain OH⁻ ions in its formula. Instead, it generates OH⁻ ions as the product of a proton-transfer reaction with H₂O molecules; NH_three acts like a Brønsted-Lowry base, and H₂O acts like a Brønsted-Lowry acrid:

A reaction with water is called hydrolysis; we say that NH_three hydrolyzes to make NH₄ ⁺ ions and OH⁻ ions.

Even the dissolving of an Arrhenius acid in h2o tin can be considered a Brønsted-Lowry acid-base reaction. Consider the process of dissolving HCl(g) in water to make an aqueous solution of muriatic acid. The process tin can be written as follows:

HCl(g) + H₂O(ℓ) → H_threeO⁺(aq) + Cl⁻(aq)

HCl(g) is the proton donor and therefore a Brønsted-Lowry acid, while H₂O is the proton acceptor and a Brønsted-Lowry base. These ii examples bear witness that H₂O can human action as both a proton donor and a proton acceptor, depending on what other substance is in the chemical reaction. A substance that tin human action as a proton donor or a proton acceptor is chosen amphiprotic. Water is probably the near mutual amphiprotic substance we volition encounter, but other substances are also amphiprotic.

Instance 3

Identify the Brønsted-Lowry acid and the Brønsted-Lowry base in this chemical equation.

C_sixH_fiveOH + NH₂ ⁻ → C₆H₅O⁻ + NH₃

Solution

The C_{half dozen}H₅OH molecule is losing an H⁺; it is the proton donor and the Brønsted-Lowry acid. The NH_ii ⁻ ion (called the amide ion) is accepting the H⁺ ion to get NH₃, and so information technology is the Brønsted-Lowry base.

Test Yourself

Place the Brønsted-Lowry acid and the Brønsted-Lowry base of operations in this chemical equation.

Al(H₂O)₆ ⁱⁱⁱ⁺ + H₂O → Al(H₂O)₅(OH)^two+ + H₃O⁺

Answer

Brønsted-Lowry acid: Al(H₂O)_vi ³⁺; Brønsted-Lowry base: H₂O

In the reaction between NH₃ and H₂O,

the chemical reaction does not go to completion; rather, the reverse process occurs likewise, and eventually the two processes cancel out any additional change. At this point, we say the chemical reaction is at equilibrium. Both processes still occur, but any net change past one process is countered by the same net alter by the other procedure; it is a dynamic, rather than a static, equilibrium. Because both reactions are occurring, it makes sense to apply a double arrow instead of a single arrow:

What practice you lot notice about the reverse reaction? The NH₄ ⁺ ion is donating a proton to the OH⁻ ion, which is accepting it. This ways that the NH₄ ⁺ ion is interim as the proton donor, or Brønsted-Lowry acid, while OH⁻ ion, the proton acceptor, is acting as a Brønsted-Lowry base of operations. The reverse reaction is also a Brønsted-Lowry acrid base reaction:

This means that both reactions are acid-base reactions past the Brønsted-Lowry definition. If you consider the species in this chemical reaction, two sets of similar species exist on both sides. Within each set, the two species differ by a proton in their formulas, and one member of the ready is a Brønsted-Lowry acid, while the other member is a Brønsted-Lowry base. These sets are marked here:

The two sets—NH₃/NH_four ⁺ and H_twoO/OH⁻—are chosen conjugate acrid-base pairs. We say that NH₄ ⁺ is the conjugate acid of NH_iii, OH⁻ is the conjugate base of H₂O, and and so forth. Every Brønsted-Lowry acid-base reaction tin be labelled with two conjugate acid-base pairs.

Example 4

Identify the conjugate acrid-base pairs in this equilibrium.

(CH₃)₃N + H₂O ⇄ (CH₃)₃NH+ + OH^–

Solution

One pair is H₂O and OH⁻, where H_iiO has one more H⁺ and is the conjugate acid, while OH⁻ has one less H⁺ and is the cohabit base of operations. The other pair consists of (CH₃)₃N and (CH_iii)₃NH⁺, where (CH₃)₃NH⁺ is the cohabit acrid (it has an additional proton) and (CH₃)_threeN is the conjugate base.

Test Yourself

Identify the conjugate acrid-base pairs in this equilibrium.

NH₂ ^–+ H_iiO ⇄ NH_three + OH^–

Reply

H₂O (acid) and OH⁻ (base); NH₂ ⁻ (base) and NH_three (acid)

Chemistry Is Everywhere: Household Acids and Bases

Many household products are acids or bases. For instance, the owner of a pond pool may use muriatic acid to clean the pool. Muriatic acrid is some other name for HCl(aq). In Chapter iv "Chemic Reactions and Equations", Department 4.5 "Neutralization Reactions", vinegar was mentioned equally a dilute solution of acetic acid [HC₂H_threeO₂(aq)]. In a medicine breast, one may observe a canteen of vitamin C tablets; the chemic name of vitamin C is ascorbic acrid (HC₆H₇O_six).

One of the more familiar household bases is NH₃, which is found in numerous cleaning products. NH₃ is a base because it increases the OH⁻ ion concentration by reacting with H_twoO:

NH₃(aq) + H₂O(ℓ) → NH₄ ⁺(aq) + OH⁻(aq)

Many soaps are also slightly basic because they incorporate compounds that act every bit Brønsted-Lowry bases, accepting protons from H₂O and forming backlog OH⁻ ions. This is one caption for why soap solutions are glace.

Perhaps the most dangerous household chemic is the lye-based drain cleaner. Lye is a mutual proper noun for NaOH, although it is also used as a synonym for KOH. Lye is an extremely caustic chemic that tin can react with grease, hair, food particles, and other substances that may build upward and clog a water pipe. Unfortunately, lye can likewise attack body tissues and other substances in our bodies. Thus when we use lye-based bleed cleaners, we must exist very careful not to bear upon any of the solid drain cleaner or spill the water information technology was poured into. Safer, nonlye drain cleaners (similar the 1 in the accompanying figure) use peroxide compounds to react on the materials in the clog and clear the drain.

Fundamental Takeaways

• A Brønsted-Lowry acid is a proton donor; a Brønsted-Lowry base is a proton acceptor.
• Acrid-base reactions include 2 sets of conjugate acid-base of operations pairs.

Exercises

1. Define Brønsted-Lowry acid. How does it differ from an Arrhenius acid?

2. Define Brønsted-Lowry base. How does it differ from an Arrhenius base?

3. Write the dissociation of hydrogen bromide in water as a Brønsted-Lowry acid-base reaction and place the proton donor and proton acceptor.

4. Write the dissociation of nitric acid in water equally a Brønsted-Lowry acrid-base reaction and identify the proton donor and proton acceptor.

5. Pyridine (C_vH₅N) acts as a Brønsted-Lowry base in water. Write the hydrolysis reaction for pyridine and identify the Brønsted-Lowry acid and Brønsted-Lowry base.

6. The methoxide ion (CH₃O⁻) acts equally a Brønsted-Lowry base in water. Write the hydrolysis reaction for the methoxide ion and identify the Brønsted-Lowry acrid and Brønsted-Lowry base.

7. Identify the Brønsted-Lowry acrid and Brønsted-Lowry base of operations in this chemic equation.

   H₃PO₄ + OH⁻ → H_twoPO_four ⁻ + H₂O

8. Identify the Brønsted-Lowry acid and Brønsted-Lowry base in this chemical equation.

   H₂C₂O_four + 2F⁻ → 2HF + C₂O₄ ²⁻

9. Predict the products of this reaction, assuming information technology undergoes a Brønsted-Lowry acid-base reaction.

   HC_twoH₃O₂ + C₅H_vNorth → ?

10. Predict the products of this reaction, assuming it undergoes a Brønsted-Lowry acrid-base reaction.

    (C₂H₅)₃Due north + H₂O → ?

11. What is the conjugate acid of H_iiO? of NH_iii?

12. What is the cohabit acid of H₂PO_iv ⁻? of NO_iii ⁻?

13. What is the cohabit base of operations of HSO₄ ⁻? of H₂O?

14. What is the conjugate base of H_iiiO⁺? of H₂SO_four?

15. Identify the cohabit acid-base pairs in this reaction.

    HSO_four ⁻ + PO_iv ⁱⁱⁱ⁻ → SO_four ²⁻ + HPO₄ ²⁻

16. Identify the conjugate acrid-base pairs in this reaction.

    HClO₃ + (C_twoH₅)_threeN → ClO₃ ⁻ + (C₂H₅)₃NH⁺

17. Identify the conjugate acid-base pairs in this reaction.

    NH₃ + C₆H₅O⁻ → C_viH₅OH + NH₂ ⁻

18. Identify the conjugate acid-base pairs in this reaction.

    C_fiveH_fiveNH⁺ + C₂O_iv ²⁻ → C₅H_fiveN + HC₂O₄ ⁻

Answers

ane.

A Brønsted-Lowry acid is a proton donor. It does not necessarily increment the H⁺ concentration in water.

three.

HBr + H₂O → H_iiiO⁺ + Br⁻; PD: HBr; PA: H₂O

5.

C₅H_vN + H₂O → C₅H₅NH⁺ + OH⁻; PD: H₂O; PA: C_vH_fiveN

7.

BL acid: H_iiiPO₄; BL base: OH⁻ 9.

C_twoH₃O₂ ⁻ and C₅H₅NH⁺ 11.

H₃O⁺; NH₄ ⁺ 13.

SO₄ ²⁻; OH⁻ 15.

HSO₄ ⁻ and so_four ⁱⁱ⁻; PO_iv ³⁻ and HPO_iv ²⁻ 17.

NH₃ and NH_ii ⁻; C₆H₅O⁻ and C₆H₅OH

What Is A Bronsted Base,

Source: https://ecampusontario.pressbooks.pub/introductorychemistry/chapter/bronsted-lowry-acids-and-bases-2/

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