Acids and Bases Acids are substances that release

Acids and Bases

Acids are substances that release hydrogen ions, H+, in solution l Acids can be recognized because their chemical formulas start with the symbol for hydrogen, H l l HCl – hydrochloric acid l H 2 SO 4 – sulfuric acid l HNO 3 – nitric acid

Bases are substances that release hydroxide ions, OH-, in solution l Many bases can be recognized because their chemical formulas end with OH l l Na. OH – sodium hydroxide l Ca(OH)2 – Calcium hydroxide

Bases A base can also be called an alkali l Remember the alkali metals – which group? l l Combine bases with hydroxide to form the strongest

The p. H Scale Used to show the strength of an acidic or basic solution l Measures the concentration of H+ ions in solution l An acid has a p. H<7 l A base has a p. H>7 l Pure water has p. H=7 (the concentrations of H+ and OH- ions are equal) l

The p. H Scale l p. H can be determined by using l Indicators (such as phenolphthalein) l Litmus and p. H papers (contain chemicals that turn certain colors in the presence of acids or bases) l p. H meter

The p. H Scale l The concentration of H+ ions is inversely proportional to the concentration of OHions l As the concentration of H+ ions increases, the concentration of OH- ions decreases l As the concentration of OH- ions increases, the concentration of H+ ions decreases

p. H of Household Chemicals You might be surprised to know that many household items are acids and bases. l We can use litmus paper and indicator to find out which are acids and which are bases. l

Conductivity Solutions that conduct electricity are called electrolytes l In order to conduct electricity, there must be charged particles in the solution l Which things will conduct electricity? l l Water l Sugar l Vinegar Salt Baking soda

Conductivity Solutions that conduct electricity are called electrolytes l In order to conduct electricity, there must be charged particles in the solution l Which things will conduct electricity? l l Salt l Sugar l Acids and bases both conduct electricity because they form ions in solutions

Other Properties Acids are corrosive, bases are caustic (both can cause burns) l Acids taste sour (think lemon juice or vinegar) l Bases taste bitter (ever tried plain baking soda? ) l Bases feel slippery because they react with the fats in your skin to make soap l

Neutralization Reactions Acids and bases combine to form a salt and water l This is called neutralization and is a double replacement reaction l HCl + Na. OH Na. Cl + H 2 O acid base salt water When the reaction is complete, the p. H will be 7, or neutral