Acids and Bases Flashcards
bronsted-lowry acid
proton (H+) donator
bronsted lowry base
proton (H+) acceptor
conjugate acid base pairs
HA + B –> A- + BH+
- conjugate acid-base pair
- conjugate acid-base pair
differ by one proton
amphiprotic
- substance that can act as both a proton donator and a proton acceptor
- must have a lone pair of electrons and hydrogen that can be released as H+
alkali
bases that dissolve in water to form the hydroxide ion
salt
- ionic compound formed when the hydrogen of an acid is replaced by a metal or another positive ion
parent acid/base
e.g. NaCl derived from acid HCl and base NaOH
acid + metal –>
salt + hydrogen
acid + carbonate –>
- salt + water + carbon dioxide
- effervescence
acid + base –>
salt + water
Neutralization
- reaction that occurs when an acid and base react together to form salt and water
- exothermic
enthalpy of neutralization
enthalpy change that occurs when an acid and a base react together to form one mole of water
effervescence
gas given off so visibly produces bubbles
acid-base indicators
change color reversibly according to concentration of H+ ions in the solution
Why do acid-base indicators work?
- indicators are weak acids or bases whose conjugates have different colors
- color change identifies pH of substance
- usually aqueous or absorbed on test paper
What is the sign of a good indicator?
gives distinct or sharp color change at equivalence point
litmus
- best known acid-base indicator
- dye derived from lichens
- pink in presence of acid; blue in presence of alkalis
universal indicator
- several indicators mixed together
- changes color many times across range of acids/alkalis
- can be used to measure [H+] on pH scale
acid-base titration
- reacting together a carefully measured volume of one of solutions, and adding the other solution gradually
- until reach equivalence point
equivalence point
where an acid and base exactly neutralize each other
What is the pH equation?
What is the [H+] equation?
- pH = -log10[H+]
- [H+] = 10-pH
What are some of the features of the pH scale?
- pH numbers usually positive
- have no units
- pH inversely related to [H+]
- change of one pH unit represents a 10-fold change in [H+]
What are the values of pH?
pH meter
- probe that directly reads [H+] through an electrode
- have accuracy to several decimal points
- must be calibrated before each use with buffer solution
- must be standardized for temperature
ionic product constant of water
- Kw = [H+][OH-]
- in pure water [H+] = [OH-]
Definitions of acidic, neutral, and alkali solutions by [H+]
- acidic solutions [H+] > [OH-]
- neutral solutions [H+] = [OH-]
- alkaline solutions [H+] -]
What is the relationship between [OH-] and [H+]?
inversely proportional in aqueous solution
strong acids/bases
- ionize almost completely in solution
- hydrochloric acid, nitric acid, sulfuric acid
- lithium hydroxide, sodium hydroxide, potassium hydroxide, barium hydroxide
weak acids/bases and examples
- ionize only partially in solution
- ethanoic acid, carbonic acid, phosphoric acid
- ammonia, ethylamine
How do you distinguish between strong acids/bases and weak acids/bases?
- strong acids/bases have higher concentration of ions than weak acids/bases
- can only compare concentrations at same temperature
electrical conductivity of strong/weak acids/bases
strong acids/bases have higher conductivity than weak acids/bases as long as same concentrations compared
rate of reaction of strong/weak acids/bases
strong acids/bases have greater rate of reaction
pH of strong/weak acids/bases
pH can be used to directly compare strengths of acids (as long as of equal molar concentration)
