ch 20 acids and bases

Question 1

define bronsted-lowry base

Answer 1

proton acceptor

Question 2

define bronsted-lowry acid

Answer 2

a proton donator

Question 3

define an alkali

Answer 3

Alkali - a base that dissolves in water forming OH- ions

Question 4

what is a conjugated base pair

Answer 4

two species that transform into each other by the gain or loss of a proton.

Question 5

what is the hydronium ion

Answer 5

H30+(dative covalent from o to h)

Question 6

monobasic, dibasic and tribasic (basic is interchangabe with protic)

Answer 6

monobasic release one h+ per olecule eg hcl
dibasic release two eg h2so4
tribasic h3po4

Question 7

MASH is what type of reaction

Answer 7

Redox

Question 8

Neutralisation

Answer 8

Neutralisation - a reaction that produces a salt and water

Question 9

in an acid base/ neutralisation reaction what are the three types of base

Answer 9

metal carbonate, metal oxide, metal hydroxide (alkali)

Question 10

pH

Answer 10

-log10[H+]

Question 11

when is [H+]=[HA]

Answer 11

when calculating the pH of a strong acid

Question 12

pH must always be given to what dp

Answer 12

2

Question 13

Ka=

also what is Ka

Answer 13

Ka(acid dissociation constant)=[A-][H+]/[HA]

Question 14

Ka can be simplified for weak acids to ….. under the assumption that …… and these assumptions break down when ………

Answer 14

ka=[H+]^2/[HA]
1. [HA]initial=[HA]final Very few HA molecules dissociate so it is
assumed that the equilibrium concentration of HA is very nearly the same as the
concentration of undissociated HA(aq).
2. [H+]=[A-] ionisation of water is negligible
The approximation assumes that [HA(aq)]start&raquo_space; [H+(aq)]eqm.

1. This approximation holds for weak acids with small Ka values, but breaks down when [H+(aq)]
   becomes significant. The approximation breaks down for stronger weak acids with Ka > 10-2
   moldm-3 and for very dilute solutions.
2. for very weak acids or very dilute pH >6

Question 15

what and why Pka and how

Answer 15

pKa is used to convert Ka into more managable values
Its calculated as pKa=-log[ka]
ka=10^-pka
strong acids: ka is large. pka is smaller
weak acids: Ka is smaller. pka is greater

i like to rember it as p like pH so Pka is similar to its ph values

Question 16

ionic product of water, when do we use it what is its formula

Answer 16

Kw=[H+][OH-]
(we dont divide by conc of h20 because its sooo vast comaped to h and oh and so we consider it constant)
at 25 degrees kw=1x10-14
pure water, neutral [OH]=[H]

we can use this ^ to calculate the ph of strong bases otherwise the method to calculate pOH=-log10[OH-]
PH=14-ans
works too :)