Chapter 10 Acids, Bases, and Salts

Electrolytes Any substance that conducts electricity in a solution is an electrolyte Ions are electrolytes ACIDS, BASES, and SALTS are all good electrolytes.

Properties of Acids Aqueous solutions conduct an electric current They are good electrolytes Sour taste. So, lemon juice is an ____. Formula usually begins with an “H” and the name ends in the word “acid.” HCl or Hydrochloric Acid pH of 0-6 We will talk more about pH later Reacts with certain metals to produce hydrogen gas. Table J, but we will go over it later Reacts with bases to form a salt and water. Called neutralization Cause indicators to change colors Table M Common acids are on Table K

Table J- Reactivity The higher up the element is, the MORE reactive it is. Any metals ABOVE **H2 react with acids to produce hydrogen gas. Zn + 2HCl => ZnCl2 + H2 Metals BELOW **H2 do NOT react with acids!

Properties of Bases Aqueous solutions conduct an electric current They are good electrolytes Bitter taste. So, coffee is a ____. Have a slippery or soapy feeling So, dish soap is a ___. Formula usually ends in -OH and the name ends in the word “hydroxide.” NaOH or Sodium Hydroxide pH of 8-14 We will talk more about pH later Reacts with acids to form a salt and water. Called neutralization Cause indicators to change colors Table M Common acids are on Table L

Defining an Acid and a Base There are 2 main theories that define an acid and a base Arrhenius Theory Bronsted-Lowry Theory

Arrhenius Theory Acids in a water solution will release H+ HYDROGEN IONS as the only positive ions in solution. Sometimes written as H3O+ Hydronium ions HCl(aq) => H+ + Cl- HCl + H2O => H3O+ + Cl- Bases in a water solution will release OH- HYDROXIDE IONS as the only negative ions in solution. NaOH(aq) => Na+ + OH-

Bronsted-Lowry Theory Acids are PROTON DONORS Bases are PROTON ACCEPTORS Think about it…. What is the charge on a proton? So, acids DONATE an H+ And, bases ACCEPT an H+

Conjugate Acid/Base Pairs Whichever compound in an equation DONATES the proton must be the ACID Whichever compound in an equation ACCEPTS the proton must be the BASE HNO3 + H2O => H3O+ + NO3- acid base acid base

Amphoteric Solutions A substance that can act as EITHER an acid or a base. H2O H2SO4

Neutralization Reaction Occurs when [H+] = [OH-] Do you remember what brackets mean? So, for complete neutralization, it must have the same concentrations and the same strength of pH Weak acid + strong base = weak base Strong acid + weak base = weak acid Strong acid + strong base = neutral Acid + Base => Salt + Water BY salt, I mean compounds that do NOT contain an H+ or an OH- ions. Net Ionic Equation for Neutralization H+ + OH- => H2O

Examples Finish the following equations: HCl + NaOH => HCl + KOH => Mg(OH)2 + HCl =>

Acid/ Base Indicators Indicates the presence of an acid or base Changes color when pH changes Table M

Table M pH of 5.4? pH of 3? Why is litmus not a good indicator of something that has a pH of 13?

pH Scale 0 – 7 – 14 0 = strong acid 6 = weak acid 7 = neutral 8 = weakest base 14 = strongest base

pH Scale A negative log scale that demonstrates the strength of an acid or a base 1 x 10-4 = pH 4 1 x 10-10 = pH 10 pH is the number of the exponent It is how many H+ ions are present Each change of 1 position on the pH scale is a change of 10x As you change from a 4 pH to a 5 pH, there are ___ times (more/less) H+ ions pH of 6 to pH of 8 ? pH of 10 to a pH of 7 ? As the concentration of the hydrogen ion increases, the concentration of the hydroxide ion decreases

Titration Used to find the unknown Molarity of an acid or a base The KNOWN variable is placed in a buret and the UNKNOWN variable is placed in a flask with a indicator (usually phenolphthalein) When the color changes, you have the volume of the KNOWN variable and can now find the molarity using a formula

Titration Color change indicates end point of titration Table T

Examples 50mL of an acid with a molarity of 10M completely neutralizes 100mL of a base. What is the molarity of the base? A 9.0mL sample of HCl solution is exactly neutralized by 6.0mL of a 3.0M NaOH solution. What is the concentration of the HCl solution? How many milliliters of 0.20M HCl are needed to exactly neutralize 40.mL of 0.40M KOH? Write the balanced equation for the reaction between HCl and KOH