15.4 NOTES Acids and Bases

C.4 Structure Determines Properties Arrhenius definition of acids and bases   Acid – a substance that generates hydrogen ions when dissolved in water Base – generates hydroxide (-OH) when dissolved in water “OH is your home base” Combining the two creates a hydronium ion (H3O+)

Most acids have hydrogen atoms that can be released in water   H ____, H2_____, H3_____ Ex: HNO3, H2S, H3PO4 Form anion and hydronium when dissolved in water

Bases have a cation and a hydroxide ion   ___OH, ___(OH)2, ___ (OH)3 Ex. NaOH, Sr(OH)2, Al(OH)3 Form cation and OH- when dissolved in water

Neutralization Mixing equal amounts of acid and base, forming water and a salt as the products A salt is made from a cation (+) and an anion (-) charge   Neutral solutions Concentrations of hydronium and hydroxide are small and equal

Acidic solutions (H+)   Hydronium concentration is higher than hydroxide (OH-) Very acidic solutions have very large hydronium concentrations Basic solutions Hydroxide(OH-) concentration in higher than hydronium (H+) Very basic solutions have very large hydroxide concentrations

The pH scale   Related to hydrogen/hydronium concentration present in solution pH stands for power of hydronium ion, where power is the power of 10 that expresses the hydrogen ion’s molar concentration

100 - 1014   Closer to 0, the more acidic the substance is, the closer to 14, the more basic the substance pOH can measure alkalinity, or how basic the solution is or how much hydroxide is present The scale is opposite the pH scale; bases are close to O and acids are close to 14

You can look at this as a number line:

C.7 Interpreting the pH Scale – Complete the following chart. Substance pH pOH Acid, Base, or Neutral Milk 6.0 8.0  Acid  Stomach Fluid  1.0 13.0  Acid Drain Cleaner  Base Cola Drink  3.0 11.0

C.8 Strengths of Acids and Bases Ionization – when acids and bases break apart into ions

Strong acids and Strong bases- break apart completely in water and don’t reform the original acid or base   There are 6 strong acids HI, HBr, HCl, HNO3, H2SO4, and HClO4, all other acids are weak Strong bases start with a cation that is in group 1 or 2 on the periodic table LiOH, NaOH, KOH, RbOH, Mg(OH)2, Sr(OH)2, Ba(OH)2 Weak acids/bases- only partially break apart in water

Reversible reactions   Weak acids can proceed at an equal rate in each direction Dynamic equilibrium Forward reaction goes at the same rate as the reverse reaction Forward/reverse rates are equal, not the amounts of products They take the same amount of time to undergo the reaction Strong acids/bases typically are not reversible

C.10 Acids, Bases, and Buffers Some lakes/rivers aren’t affected by acid rain   Buffers Substances capable of neutralize an acid or base without changing the pH need: To neutralize an acid, you add a base To neutralize a base, you add an acid Natural buffers are found in blood and stomach

Strength vs. Concentration   Strength – measure of how many ions are produced when acid/base is dissolved in water Strong acid/base – all (or nearly all) acid/base have reacted with water to produce ions Weak acid/base – acid/base has partially formed ions in water

Concentration – measure of how many particles (molecules or ions) are dissolved in a solutions   Concentrated acid/base – a very large number of particles are dissolved Dilute acid/base – a low number of particles are dissolved

True or false It is possible to have a strong acid that is dilute True It is possible to have a weak base that is concentrated true