Chemistry in Action Acids and bases Unit 1 Science 20F Chemistry in Action Acids and bases

Acids and Bases There are special compounds that have very specific properties Acid is a covalent compound that has an H+ ion upon dissociation In other words, most acids start with a hydrogen ex: HCl, HNO3, H2SO4 One major exception is acetic acid, CH3COOH

Base is an ionic compound that gives off an OH- ion upon dissociation In other words, bases all end in OH ex: NaOH, KOH, Al(OH)3 One major exception to this rule is ammonia, NH3 Salt is an ionic compound that doesn’t give H+ or OH- ions upon dissociation ex: NaCl, MgBr2, KNO3

Properties of Acids and Bases a) they ionize in water b) acids react with metal to make H2 gas c) acids turn blue litmus red d) acids neutralize bases e) acids have a sour taste

Properties of Bases: a) bases are electrolytes b) bases turns red litmus blue c) bases neutralize acids d) bases taste bitter and feel slippery e) bases dissociate because they are ionic Acids and bases can be rated for strength based on a special scale called the pH scale

Developed in 1909 by Soren Sorenson It refers to the power of the H+ concentration in a solution The actual scale looks like: neutral increasing acidity increasing basicity vinegar 1 2 3 11 14 6.5 7 Digestive juices/ Coke Milk of Magnesia Milk

To test if a substance is an acid or a base we can use chemicals called “indicators”. The most common indicator is litmus paper. It turns red if in an acid and blue if it’s in a base. Sometimes we’d like to have a more specific idea of the pH so we use liquid indicators. Some examples of liquid indicators include phenolphthalein, bromothymol blue, universal indicator, etc…

Naming Acids and Bases There are two possibilities when trying to name acids: 1) Hydrogen plus one other element Name these as “hydro ______ic acid” ex: HCl is hydrochloric acid H2S is hydrosulfuric acid 2) Hydrogen plus a complex ion Name these as “_______ic acid” ex: H2SO4 is called sulfuric acid H3PO4 is called phosphoric acid

Bases are simple to name Bases are simple to name. Just write the first element’s name followed by “hydroxide” ex: NaOH is sodium hydroxide Al(OH)3 is aluminum hydroxide

Neutralization Reactions When a strong acid and a strong base mix together they neutralize each other They will always make water and a salt (some ionic compound) It will be your job to figure out what that salt is. Write water as HOH Don’t forget to criss-cross the salt because it is an ionic compound!

ex: HCl + NaOH → HOH NaCl HCl + NaOH → HOH + NaCl ex 2: H2SO4 + KOH → K2SO4 HOH H2SO4 + KOH → HOH + K2SO4 2 2