Flashcards
ionic eqm
Flashcards do conjunto (23)
- 1ionic pdt of water, Kw=[H+][OH-]=_(value)_10^(-14)
- 2what is the conc. of H+ and OH- in pure water at 25°C?[H+]=[OH-]=10^(-7)
- 3relationship between pH and pOH @ 25°CpH+pOH=14
- 4when to consider contribution of [H+/OH-]?for very dilute solutions, when [acid/base]<10^-5
- 5formula for Ka, pKa and derived KaKa=[A-][H+]/[HA]
pKa=-lg10Ka
Ka=10^(-pKa) - 6what is the formula for the approximation method used for weak acids/ bases?[H+]=√(c × Ka)
[OH-]=√(c × Kb) - 7relationship between Ka & Kb @ 25°C?Ka*Kb = Kw = 10^(-14)
- 8what is a buffer solution?a buffer solution is one which is capable of maintaining a fairly constant pH when small ants of acid or base are added to it.
- 9components of acidic & basic buffer sltns:acidic: weak acid & salt of conj base
basic: weak base & salt of conj acid - 10what is the formula for an acidic buffer?pH=pKa + lg([salt]/[acid])
- 11explain how an acidic buffer works:when a small amt of acid, H+, is added:
(eqn)
the added H+ is removed as ___
[H+] is slightly changed hence pH remains fairly constant.
when a small amt of base, [OH-]. is added:
(eqn)
the added OH- is removed as ___ and H2O
[OH-] is slightly changed hence pH remains fairly constant. - 12method for solving pH problems involving acidic buffer solutions:1. identify the components of the buffer
2. calculate eqm [ ] of buffer components.
(beware of changes in [ ], due to changes in total volume when mixing]
3. sub eqm [ ] into pH expression of a buffer - 13when does maximum buffer capacity occur?max buffer capacity occurs when the sltn contains equal [ ] of weak acid/ base and its salt.
[salt] = [acid] and pH=pKa
[salt] = [base] and pOH=pKb
{at half equivalence point} - 14name of indicators and range of pH change- phenolphthalein: 8.0 - 10.0
- methyl orange: 3.0 - 4.5 - 15what is the equivalence point?it is when all of the base has reacted with all of the acid.
i.e. mid-point of steep slope. - 16how to calculate exact pH at equivalence point?pH at equivalence point = pH of salt formed
- 17how to calculate final pH of titration?calculate the volume, then moles, then concentration, of the excess reagent added.
OR
final pH due to buffer solution - 18formula for solubility product:Ksp = [M+][X-]
- 19what is solubility product (Ksp)it is an equilibrium constant which is the product of the molar concentrations of the dissolved dissociated ions each raised to its appropriate power, in a saturated solution of the salt at a given temperature
- 20what is solubility?it is a concentration term which refers to the maximum amt of the solute that can be dissolved per dm^3 of solvent to make a saturated solution at a given temperature
- 21define common ion effect:the solubility of a sparingly soluble salt is reduced in the presence of a common ion from an external source.
- 22when will precipitation of a sparingly soluble salt occur?when ionic product > Ksp
- 23method for solving precipitation problems involving sparingly soluble salt:1. write partial dissociation eqn for sparingly soluble salts
2. write ionic pdt expression
3. define ion [ ] at pt of mixing
4. sub. aq ion [ ] into ion pdt expression and compare with Ksp
Informações
- Descrição
- a levels chemistry FlashCards sobre ionic eqm, criado por omnommables em 26-06-2014.
- Criado por
- omnommables · jun 2014
- Atualizado
- 29 jun 2016
- Visualizações
- 102
- Avaliação