Acids and Bases

An acid is a compound that dissolves in water to form a solution with a pH lower than 7. A base is a compound that dissolves in water to form a solution with a pH greater than 7. ACIDS AND BASES

Saliva is basic so acids won’t corrode your teeth Stomach is acidic to activate pepsin Pancreas produces sodium bicarbonate to neutralize both acids and bases in the blood. Buffer ACIDS IN YOUR BODY

Indicators change colour depending on the pH of a solution. Litmus indicators turn blue in a base and red in an acid. A universal indicator is a mixture of several indicators that change colour as the acidity changes. INDICATORS

The pH scale is a measure of acidity Neutral substance has a pH of 7 at 25°C. Acidic substances are below 7. The closer the pH is to 0, the more acidic the substance is. Basic substances are above 7. The closer to 14, the more basic it is Every increase of 1on the pH scale indicates an increase of 10 in how basic a substance it is. A solution with a pH of 9 is ten times more basic than one with a pH of 8. PH SCALE

PropertyAcidBase TasteSourBitter TouchNot slipperySlippery Reaction with metalsMetal corrodes, H 2 bubblesNo reaction Litmus indicatorRedBlue Electrical conductivityConductive pH of solution<7>7 PROPERTIES OF ACIDS AND BASES

You can usually determine whether a compound is an acid by looking at the formula…if there is an H on the left side of the formula (HCl) or an H on the right side of an organic acid group (-COOH). IUPAC recommends naming acids as aqueous substances. Ex. HCl is aqueous hydrogen chloride Acids also have different naming systems…acids that contain hydrogen and one other non-metallic element can be written with the prefix ‘hydro-’ and the suffix ‘- ic.’ Ex. HCl is hydrochloric acid NAMING ACIDS

Acids that contain oxygen follow a system based on the anion. If the anion ends in ‘-ate’ then the acid ends in ‘-ic.’ Ex. H 2 SO 4 is sulfuric acid NAMING ACIDS CONT’D

Ionic nameAcid nameExample Simple ionHydrogen ____ideHydro____ic acidH 2 S hydrosulfuric acid Complex Ions Hydrogen per ___atePer_______ic acidH 2 SO 5 persulfuric acid Hydrogen _____ate_________ic acidH 2 SO 4 sulfuric acid Hydrogen _____ite_________ous acidH 2 SO 3 sulfurous acid Hydrogen hypo__iteHypo____ous acidH 2 SO 2 hyposulfurous acid NAMING ACIDS CONT’D

All acids start with H (e.g. HCl, H 2 SO 4 ) 2 acids types exist: binary acids and oxyacids Binary: H + non-metal. E.g. HCl Oxy: H + polyatomic ion. E.g. H 2 SO 4 Each have different naming rules. Binary acids: naming depends on state of acid If it’s not aqueous: hydrogen + non-metal HCl(g) = hydrogen chloride If it is aqueous: hydro + non-metal + ic acid HCl(aq) = hydrochloric acid (aqueous hydrogen chloride) NAMING ACIDS: BINARY ACIDS HBr(s) HI(aq) H 2 S(aq) H 2 S(g) hydrogen bromidehydr(o)iodic acid hydrogen sulfidehydrosulfuric acid

Naming does not depend on the state (aq) 1) name the polyatomic ion 2) replace ate with ic, ite with ous 3) change non-metal root for pronunciation 4) add “acid” to the name E.g. H 2 SO 3 NAMING ACIDS: OXYACIDS HNO 2 hypochlorous acid H 3 PO 4 (aq) carbonic acid 1) sulphite,2) sulphous, 3) sulphurous, 4) sulphurous acid

Naming does not depend on the state (aq) 1) name the polyatomic ion 2) replace ate with ic, ite with ous 3) change non-metal root for pronunciation 4) add “acid” to the name E.g. H 2 SO 3 NAMING ACIDS: OXYACIDS HNO 2 nitrous acid hypochlorous acid HClO H 3 PO 4 (aq) phosphoric acid carbonic acid H 2 CO 3 1) sulphite,2) sulphous, 3) sulphurous, 4) sulphurous acid

a) chloric acid b) hydrosulfuric acid c) hydrobromic acid d) phosphorous acid e) iodic acid f) HCl(g) g) HCl(aq) h) H 2 SO 4 (s) i) H 2 SO 4 (aq) j) HClO 2 k) HF(aq) ASSIGNMENT: GIVE FORMULA OR NAME a) HClO 3 b) H 2 S(aq) c) HBr(aq) d) H 3 PO 3 e) HIO 3 f) hydrogen chloride g) hydrochloric acid h) sulfuric acid i) sulfuric acid j) chlorous acid k) hydrofluoric acid

When the hydroxide (OH - ) ion is present with the ammonium ion or a metal ion, it is basic. RECOGNIZING BASES BY THEIR FORMULAS

Bases contain an OH group C 6 H 12 O 6 does not have an OH group If an OH group is present it will be clearly indicated: e.g. NaOH, Ca(OH) 2 Also notice that bases have a metal (or positive ion such as NH 4 + at their beginning) Bases are named like other ionic compounds: +ve is named first, followed by the polyatomic ion NAMING BASES - calcium hydroxide - copper(I) hydroxide - Al(OH) 3 - NH 4 OH Ca(OH) 2 CuOH aluminum hydroxide ammonium hydroxide

When acids and bases react together, both acidic and basic properties disappear. This is neutralization. It produces water and a salt. NEUTRALIZATION