Acids and Bases (You may not know it, but they’re everywhere!!)

Everyday Acids  Acids make food taste sour  Lemon and orange juice contains citric acid  Vinegar contains acetic acid  Milk products (and sore muscles) contain lactic acid  Stomach acid helps digest food  Car batteries contain sulfuric acid

Everyday Bases  Soaps and cleaners contain bases  Ammonia (NH 3 )  Bleach (NaClO)  Antacids contain bases  Milk of magnesia is magnesium hydroxide  Baking soda is sodium bicarbonate (NaHCO 3 )

Physical Properties of Acids and Bases PropertyAcidsBases Colour of Red Litmus PaperNo change (red)Blue Colour of Blue Litmus PaperRedNo change (blue) Colour when Phenolphthaline Indicator is added No change (clear and colourless) Bright pink Colour when Red Cabbage Juice Indicator is added RedYellow TasteSourBitter TextureWater-likeSlippery Solubility in Water  Very good  Form ions  Very good  Form ions Electrical Conductivity  Very good because acids form ions in water  Very good because bases form ions in water

Chemical Properties of Acids and Bases PropertiesAcidsBases Chemical Reactivity  Very corrosive  React with some metals to produce H 2 gas  React with carbonates  React with bases to produce a salt and water (neutralization reactions)  Somewhat corrosive  Break down proteins (denaturation reactions)  React with acids to produce a salt and water (neutralization reactions) Commercial Uses  Used as catalysts  Used in refining oil, making fertilizers, electroplating metals  Used in antacids, cleaners

Acids and Bases “Ionize” in Water  This means that the bonds between ions in acids (or bases) break when they dissolve in water  That leaves the ions free to float around separately  That’s what makes acids and bases good conductors of electricity! H2O H+ Cl- H2O

Acids are Proton (H + ion) Donors  When dissolved in water, one of the ions that an acid releases is H+  Strong acids are 100% (or nearly so) ionized in water  Therefore, they are good H+ donors HCl H 2 SO 4 HNO 3 hydrochloric acid sulfuric acid nitric acid  Weak acids are usually less than 5% ionized in solution  Therefore, they are poor H+ donors H 3 PO 4 HC 2 H 3 O 2 phosphoric acidacetic acid

Bases are Proton (H+ ion) acceptors  Bases also ionize in solution  One of the ions released by a base is often an hydroxide ion (OH-) NaOHKOH Ca(OH) 2 sodium hydroxide potassium hydroxide calcium hydroxide  Bases are also classified as weak or strong based on the degree of ionization in water  The OH- from a base, combines with the H+ from an acid to form water H+ + OH- → H 2 O

Acids and Bases “Neutralize” Each Other  Acids and bases react in “NEUTRALIZATION” reactions  The reactants are always an acid and a base  The products always include a salt and water HCl + NaOH → NaCl + H 2 O acid base salt water

Measuring Acids and Bases  Acids and bases have a unique scale for measuring their relative strength  It’s called the pH scale  pH stands for the “power of hydrogen” because the scale is based on the concentration of H+ ions in solution  The scale goes from 0 to 14  Acids have a pH less than 7 (H+ > OH-)  Bases have a pH greater than 7 (H+ < OH-)  Distilled water has a pH of 7 which is neutral (H+ = OH-)

The pH Scale NeutralVery AcidicVery Basic (Alkaline) more H+ than OH-more OH- than H+ H+ equals OH-  The pH scale is logarithmic  That means that the space between successive numbers represents a 10X increase or decrease