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Acids/ Bases

Acids/ Bases. Assign.# 13.4. Neutralization Reactions. Recall, one of the most common types of reactions are acid/base reactions or neutralization reactions We have various definitions of acids and bases, but they all react with characteristic properties.

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Acids/ Bases

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  1. Acids/ Bases Assign.# 13.4

  2. Neutralization Reactions • Recall, one of the most common types of reactions are acid/base reactions or neutralization reactions • We have various definitions of acids and bases, but they all react with characteristic properties. • NOTE – We will review some of the material from last year, but it is expected that you study all material previously taught.

  3. Arrhenius Acid/Base • Arrhenius’ theory of acids/bases focuses on what molecules contain • An Arrhenius acid contains a H+ • An Arrhenius base contains an OH-

  4. Bronsted – Lowry Acid/Base • When Arrhenius’ definition covers many acids/bases, acid/base reactions are not about containing H+ or OH- • A Bronsted-Lowry acid is any compound that gives H+ during the reaction • A Bronsted-Lowry base is any compound that accepts H+during the reaction. • We will use this definition most of the time in this class

  5. Lewis Acid/Base • Ultimately, acid/base reactions are not about H+, but about the accepting or donating of electron pairs. • A Lewis acid is an electron pair acceptor • A Lewis base is an electron pair donor • Every acid/base in the previous two categories are also acids/bases in this category • Broadest definition

  6. Class Example • Identify the acid/base as Arrhenius, Bronsted – Lowry, and/or Lewis:

  7. Table Talk • Identify the acid/base as Arrhenius, Bronsted – Lowry, and/or Lewis:

  8. Strong vs. Weak Acid/Base • Acids/Bases can be classified as strong or weak based on how much it disassociates. • Disassociate – To break apart • Acids/Bases that completely dissociate are called strong acids/bases • Acids/Bases that only partially dissociate are called weak acids/bases. These are in equilibrium with one another

  9. Dissociation

  10. Strong Acids/Strong Bases to Memorize Strong Bases Strong Acids • LiOH • NaOH • KOH • RbOH • CsOH • Ca(OH)2 • Sr(OH)2 • Ba(OH)2 • HBr • HCl • HI • HNO3 • H2SO4 • HClO3 • HClO4

  11. I. pH • The concentrations of acids and bases are often very low. • We use the pH scale to convey the concentration of H+ • The pH scale is 0-14. • Acid = pH 0-7 • Base = pH 7-14 • Neutral chemicals = pH of 7.

  12. pH/pOH • We calculate the pH by: pH=-log([H+]) • We calculate pOH by: pOH=-log([OH-]) • For strong acids and bases, the concentration of the compound is the [H+] or [OH-] • For bases, we only know [OH-], so we need to first calculate pOH and then convert to pH using the equation: pH = 14 – pOH

  13. Class Example • What is the pH of a 0.231 M solution of NaOH?

  14. Table Talk • What is the pH of a 0.512 M solution of HNO3?

  15. Conjugate Acid/Base Pairs • As with any reaction, there is a forward and reverse reaction for acid/base reactions. • Consider the following example: HX + H2O H3O+ + X- • In the forward reaction HX is the acid because it donates H+ and H2O is the base because it accepts H+. • In the reverse reaction, H3O+ is now the acid and X- is now the base. • The pair of HX and X- are known as an conjugate acid-base pair ⇌

  16. Conjugate Acid/Base Pairs • Every acid has a conjugate base that is formed when a proton (H+) is removed • Every base has a conjugate acid that forms when a proton is added

  17. Class Example • Identify the acid, base, conjugate acid, and conjugate base in the following reaction. Identify the acid/base as Arrhenius, Bronsted – Lowry, and/or Lewis: NH3 + H2O  NH4+ + OH-

  18. Table Talk • Identify the acid, base, conjugate acid, and conjugate base in the following reaction. Identify the acid/base as Arrhenius, Bronsted – Lowry, and/or Lewis: HSO3- + H2O  SO32- + H3O+

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