ACIDS AND BASES

ACIDS & BASES Acids are substances that produce hydrogen ion in solution. (H + (aq) ) Bases are substances that produce hydroxide ions in solution. (OH - (aq) ) ACIDSBOTHBASES  Sour tasting  Produce H + ions  Turns blue litmus red  pH 0-6 React with metals to produce H 2 (g)  Clear and colorless in solution  Can be dangerous  Bitter tasting  Produce (OH) - ions  Turns red litmus paper blue  pH 8-14

pH Scale Measures acidity or basicity of solutions pH scale is measured from pH = 0-14 pH < 7 – Acidic pH = 7 - Neutral pH > 7 – Basic Very high and low pH solutions are harmful Water is neutral, because H + and OH - ions balance H 2 O  H + + OH -

Indicators substances that change color as the concentration of H + or OH - ions changes. they indicate pH Examples: litmus paper, phenolphthalein, universal indicator Blue Litmus paper turns red – Acid Red Litmus paper turns blue - Base Most indicators work only over a short range of pH values. Universal indicator (or pH paper) contains a number of indicators that change color at different pH values.

REACTIONS Metals react with acids to form hydrogen gas and a salt. Ex. Mg (s) + 2HCl (aq)  H 2(g) + MgCl 2(aq) Magnesium metal + hydrochloric acid  hydrogen gas + magnesium chloride salt Acids react with bases to form water and a salt. This process is called neutralization. Ex. HCl (aq) + NaOH (aq)  NaCl (aq) + H 2 O (l) Hydrochloric acid + sodium hydroxide base  sodium chloride salt + water [Note that this is a double displacement reaction] Tomorrow: ACID/BASES LAB