Acids and Bases Ch. 8.3 & 8.4

Acids - Names and Formulas 2 types of acids: binary & ternary. Binary acids consist of hydrogen and a negative ion (anion). Ex: hydrochloric acid, HCl, & hydrosulfuric acid, H2S. Ternary acids consist of hydrogen and a polyatomic anion. Ex: sulfuric acid, H2SO4, & nitric acid, HNO3. You can usually recognize an acid by the hydrogen at the beginning of the formula.

Bases - Names and Formulas Many bases have the hydroxide ion OH- in the formula. Ex: sodium hydroxide, NaOH & calcium hydroxide, Ca(OH)2. Ammonia, NH3, is a common base whose formula does not include the hydroxide ion.

Arrhenius Definitions An acid is a substance that produces the hydronium ion H3O+1 in aqueous solution. Consider the reaction of HCl gas in water: HCl + H2O  H3O+1 + Cl-1

Arrhenius Definitions A base is a substance that produces the hydroxide ion OH-1 in aqueous solution. Consider the following reaction: NaOH Na+1 + OH-1 NaOH produces the hydroxide ion in water solution.

Bronsted-Lowry Definitions An acid is proton (H+1) donor and a base is a proton (H+1) acceptor. Consider the reaction of hydrogen fluoride with water. HF + H2O  H3O+1 + F-1 The H+1 moves from HF to water in the forward direction.

HF + H2O  H3O+ + F-1 HF is the proton donor (acid) and water is the proton acceptor (base) in the forward direction In the reverse direction, the H+1 moves back from the H3O+1 to the F-1. This makes the hydronium ion the acid & the fluoride ion the base.

Water Water can behave as either an acid or as a base, and is said to be amphoteric. Water can undergo autoionization: H2O → H+ + OH-

Acid Properties Acids taste sour & will burn the skin. Acids turn blue litmus paper red & are colorless in phenolphthalein. Acids react with metals to produce hydrogen gas Ex: Mg + 2HCl  MgCl2 + H2

Basic Properties Bases have a bitter taste, slippery feel & will blister the skin. Bases turn red litmus paper blue & are dark pink in phenolphthalein. Bases react with acids to form a salt & water Ex: NaOH + HCl  NaCl + H2O

Acidic Anhydrides Nonmetallic oxides, called acidic anhydrides, react with water to form acids. Examples include CO2 and N2O5. CO2 + H2O  H2CO3 N2O5 + H2O  2HNO3

Basic Anhydrides Metallic oxides, called basic anhydrides, react with water to form bases. Examples include Na2O and CaO. Na2O + H2O 2NaOH CaO + H2O  Ca(OH)2

The pH Scale pH is a logarithmic scale used to indicate the concentrations of acids and bases within a certain range. Neutral solutions have a pH = 7. Further away from 7 = stronger Bases have a pH greater than seven, and acids have a pH less than seven. 0 7 14 Acids Neutral Bases

Acids are defined as those solutions that have a pH less than 7 (i. e Acids are defined as those solutions that have a pH less than 7 (i.e. more hydrogen ions than water); Bases are defined as those solutions that have a pH greater than 7 (i.e. less hydrogen ions than water).

pH of Strong Acids Strong acids are 100% ionized in water. Strong acids are HCl, HBr, HI, HClO4, H2SO4 and HNO3. For example, the following reaction goes 100% in the forward direction: HCl + H2O  H3O+1 + Cl-1 This means that all of the HCl forms hydronium ions.

The concentration of an acid should be part of the bottle label. For a strong acid the concentration listed on the bottle label is the concentration of the hydronium ion. This is because all the acid molecules are ionized & form hydronium ions.

pH for Strong Bases Strong bases undergo 100% dissociation in water. Strong bases are hydroxides of Groups 1 and 2. For example, the following process goes 100% in the forward direction: NaOH  Na+1 + OH-1 This means that all of the NaOH forms hydroxide ions.

The concentration of an base should be part of the bottle label. For a strong base, the concentration listed on the bottle label is the concentration of the hydroxide ion. This is because all of the base ions are dissociated & form hydroxide ions.

Weak Acids & Weak Bases Weak Acids undergo only partial ionization Weak Bases undergo only partial dissociation

Neutral solution, pH = 7 Acidic solution, pH < 7 Basic solution, pH > 7

Litmus Paper Base will turn red litmus paper blue Acid will turn blue litmus paper red Hydrangea = more acidic = blue More basic = pink flowers Neutral soil = both blue & pink

Neutralization & Salts Reaction b/t Acid & Base = neutralization Neutralization produces Salt & Water Ex: Squeezing Lemon Juice (contains citric acid) over Fish (contains bases) = neutralizes bitter taste

Buffers Any solution that is resistant to large changes in its pH level Made from mixing a weak acid w/ its salt or mixing a weak base w/ its salt

Electrolytes – What & Why? Electrolytes are what your cells (nerve, heart, muscle) use to carry voltages and electrical impulses (nerve impulses, muscle contractions) to other cells. Kidneys work to keep electrolyte concentrations in your blood constant despite changes in your body. (i.e. - when you exercise, you lose electrolytes (Na & K) through sweat. These electrolytes must be replaced to keep the electrolyte concentrations of your body fluids constant.

Major electrolytes your body needs sodium (Na)+1 potassium (K)+1 chloride (Cl)-1 calcium (Ca)2+ magnesium (Mg)2+ bicarbonate (HCO)3- phosphate (PO4)2- sulfate (SO4)2-

Electrolytes – Where? Electrolytes = substance that ionizes or dissociates into ions when dissolved in water Many sports drinks have NaCl or KCl added. They also have sugar & flavorings to provide your body w/ extra energy & make the drink taste better Ex: Gatorade helps restore the balance of electrolytes in your body. (Pedialyte for small children & athletes? – less carbs) Strong acids & strong bases are strong electrolytes because they dissociate or ionize almost completely in water.

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