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Acids and Bases. Dissociation. In water all ionic compounds dissociate into its ionic parts So NaCl in water dissociates into Na + and Cl - So H 3 PO 4 dissociates into 3H + and PO 4 -3 Remembers ionic compounds are formed by metals and nonmetals or by metals and polyatomic ions.
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Dissociation • In water all ionic compounds dissociate into its ionic parts • So NaCl in water dissociates into Na+ and Cl- • So H3PO4 dissociates into 3H+ and PO4-3 • Remembers ionic compounds are formed by metals and nonmetals or by metals and polyatomic ions
Identifying an Acid • An acid is any compound that forms an H3O+ (called hydronium) ion in water • Usually acids have an H in front of the compound • In general they have a sour taste and react with most metals
Naming Acids • Look at the acid’s chemical formula, try to name it as if it where an ionic compound • Then eliminate the 1st word • If no “O” is in anion then add hydro to the beginning and trade the –ide for –ic • If the anion has “O” then trade –ate or –ic if the anion ended in –ate originally • If anion has “O” then trade –ite or –ous if the anion ended in –ite originally • Finally add the word “acid” to the end-
Name these acids • HBr • H3N • H2SO4 • HI • HNO3 • HNO2
Identifying a Base • A base is any compound that forms an OH- ion (called hydroxide) in water • Usually bases have an OH at the end of the compound • Bases usually have a bitter taste and a slippery feel
Neutralization • When an acid and base react it is called a neutralization reaction • During this reaction a salt and water is always formed • Common salts include but are not limited to: • NaCl, Na2CO3, KCl, KI, MgCl2, CaCO3, and NH4NO3
Proton Donors and Acceptors • Acids are generally defined as proton donors (meaning they give away the H+) • Bases are generally defined as proton acceptors • These alternate definitions of acids and bases help us when compounds react with water or are insoluble
Acid Strength • Acids and bases are rated on a pH scale • Where 1 is the strongest acid and 14 is the strongest base • 7 is neutral (water is the only neutral compound) • 1-4 (stronger acid) • 4-7 (weak acid) • 7-10 (weak base) • 10-14 (strong base)
Acid Strength (ctd.) • Between any 7 and 6 an acid gets 10 times stronger, between 7 and 5 an acid gets 100 times stronger the scale it logarithmic • Strength is defined as how easily the H+ or the OH- comes off the acid or base, the easier it comes off the stronger the acid or base • Strength is COMPLETELY different than concentration
Concentration vs Strength • Concentration refers to how diluted an acid or base is • Concentration DOES NOT change the pH of an acid or base • Hence the pH of 16M HCl is equal to the pH of .001M HCl though there concentrations are extremely different