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Understanding Brønsted-Lowry Acid-Base Theory and Neutralization Reactions

This article explores the Brønsted-Lowry acid-base theory, defining acids as proton donors and bases as proton acceptors. It delves into the process of neutralization, illustrating how weak acids and bases interact to form conjugate pairs. Through examples, such as HF with H2O and NH3 with H2O, we can see the transformations of these substances during reactions. Furthermore, the unique role of water is highlighted, showing its amphoteric nature. By comprehending these concepts, readers will gain insight into essential chemical reactions.

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Understanding Brønsted-Lowry Acid-Base Theory and Neutralization Reactions

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Presentation Transcript

  1. Brønsted/Lowry Neutralization

  2. What is an acid? • Brønsted/Lowry acid: a proton donor proton donor?... a proton is also an H+ ion • in water, H2O + donatedH+ H3O+ • H3O+= “hydronium ion”

  3. What is a base? • Brønsted/Lowry base: a proton acceptor proton acceptor?... any substance that will take an H+ ion • in water, H2O+ base  OH- + Hbase

  4. Brønsted/Lowry “Neutralizations” • Acid1+ Base1 Acid2 + Base2 • For weak acids and weak bases • Note the double arrow!

  5. Acid1+ Base1 Acid2 + Base2 • Acid1 H++ Base2 • Acid1 donates H+ and becomes Base2, its “conjugate base” • H+ + Base1Acid2 • Base1 accepts the H+ from Acid1 and becomes Acid2, its “conjugate acid”

  6. Brønsted/Lowry examples • Examples… HF + H2O  F- + H3O+ • HF donates an H+…so it is an “acid” • H2O takes the H+ from the HF… so it is the “base”

  7. Cont… HF + H2O  F-+ H3O+ • Look at the “reverse” reaction • which donates an H+?...it is an “acid” H3O+ • which takes the H+ from the H3O+?...it is the “base” F-

  8. Cont… HF + H2O F-+ H3O+ • HF –a weak acid –becomes F-, a base • H2O, acting as a base, becomes H3O+,an “acid” • The acid becomes its “conjugate base” • The base becomes its “conjugate acid”

  9. Another example NH3 + H2O  NH4+ + OH- • H2O donatesan H+... So it is an “acid” • NH3 takes the H+ from the H2O… so it is the “base”

  10. Cont… NH3+ H2O NH4++ OH- • H2O–a weak acid –becomes OH-, a base • NH3, acting as a base, becomes NH4+,an “acid” • The acid becomes its “conjugate base” • The base becomes its “conjugate acid”

  11. Brønsted/Lowry neutralization Their conjugate acid and base A weak acid + A weak base Remember… • Weak acids lose an H+ and become their conjugate bases • Weak bases gain an H+ and become their conjugate acids

  12. Did you notice? • …that H2O was listed as an acid, and as a base, but a pure H2O solution has pH = 7? • H2O can act as an acid (lose an H+) or a base (accept an H+) depending on what it is combined with • AMPHOTERIC: act as an acid when with a base; act as a base when with an acid

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