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Acids and Bases. (p. 256-261, 264-265). Acids. Taste sour. Acids. Ionize when dissolved in water (they dissociate into their ions; +, -). This allows the water to conduct electricity (which means they are electrolytes ). Ex- HCl is an acid…when placed in water, it becomes H+ and Cl -.
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Acids and Bases (p. 256-261, 264-265)
Acids • Taste sour
Acids • Ionize when dissolved in water (they dissociate into their ions; +, -). • This allows the water to conduct electricity (which means they are electrolytes). • Ex- HCl is an acid…when placed in water, it becomes H+ and Cl-
Acids • Acids produce Hydrogen Cations • Therefore, the formula for an acid must have H in it (usually it will be at the beginning of the chemical formula only) • Ex. HCl, H2SO4
Acids • The H+ will attach to H2O to form Hydronium ions (H3O+) • Acids produce H3O+ in water
Strong vs. Weak AcidsSee Table on p. 258 Strong Acid • Ionize completely • HNO3+ H2O H3O+ + NO3- • strong electrolytes • (can conduct electricity well) Weak Acid • Don’t ionize completely (don’t produce as many ions) • CH3COOH + H2O H3O+ + CH3COO- • weak electrolytes
BASES • Taste Bitter and Soapy • Feel Slippery
Bases • Some contain hydroxide ions, OH- , in their formulas, others don’t. • Those that don’t have OH in the formula will react with water to produce OH- ions. • All produce hydroxide ions, OH- , in water & conduct electricity (electrolytes).
Strong vs. Weak Bases Strong Bases • Have OH and a metal atom in their formula • (ex-NaOH) • Dissociate in water to give: OH- & metal ion • ex. NaOH OH- + Na+ • Strong electrolyte Weak Bases • Don’t have OH in their formula • (ex-NH3) • ionize in water to produce OH- (water gives up an H), but doesn’t ionize completely • ex. NH3 + H2O NH4++ OH- • Weak electrolyte
pH Scale • Ranges from 0-14 • 7=neutral (not acidic nor basic), • Amount of H3O+ is equal to amount of OH- • Low pH (0-<7) = acidic • Amount of H3O+ is greater than the amount of OH- • pH of 3 is more acidic than a pH of 5 • High pH (>7-14)= basic • Amount of H3O+ is less than the amount of OH- • pH of 13 is more basic than a pH of 10