1034139
Description
Flashcards by omnommables, updated more than 1 year ago
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Created by omnommables
almost 10 years ago
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| Question | Answer |
| ionic pdt of water, Kw=[H+][OH-]=_(value)_ | 10^(-14) |
| what is the conc. of H+ and OH- in pure water at 25°C? | [H+]=[OH-]=10^(-7) |
| relationship between pH and pOH @ 25°C | pH+pOH=14 |
| when to consider contribution of [H+/OH-]? | for very dilute solutions, when [acid/base]<10^-5 |
| formula for Ka, pKa and derived Ka | Ka=[A-][H+]/[HA] pKa=-lg10Ka Ka=10^(-pKa) |
| what is the formula for the approximation method used for weak acids/ bases? | [H+]=√(c × Ka) [OH-]=√(c × Kb) |
| relationship between Ka & Kb @ 25°C? | Ka*Kb = Kw = 10^(-14) |
| what 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. |
| components of acidic & basic buffer sltns: | acidic: weak acid & salt of conj base basic: weak base & salt of conj acid |
| what is the formula for an acidic buffer? | pH=pKa + lg([salt]/[acid]) |
| explain 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. |
| method 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 |
| when 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} |
| name of indicators and range of pH change | - phenolphthalein: 8.0 - 10.0 - methyl orange: 3.0 - 4.5 |
| what 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. |
| how to calculate exact pH at equivalence point? | pH at equivalence point = pH of salt formed |
| how 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 |
| formula for solubility product: | Ksp = [M+][X-] |
| what 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 |
| what 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 |
| define common ion effect: | the solubility of a sparingly soluble salt is reduced in the presence of a common ion from an external source. |
| when will precipitation of a sparingly soluble salt occur? | when ionic product > Ksp |
| method 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 |
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