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Description
Flashcards by Helena Wignall, updated more than 1 year ago
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Created by Helena Wignall
over 6 years ago
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| Question | Answer |
| What is a Bronsted-Lowry Acid? | Proton Donor |
| What is a Bronsted Lowry base? | Proton Acceptor |
| What is a Strong Acid? | an acid that fully dissociates in water e.g. HCl, H2SO4 |
| what is a strong base? | a base that fully dissociates in water e.g. NaOH, KOH |
| what is a weak acid? | an acid that only slightly dissociates in water e.g. ethanoic acid |
| what is a weak base? | a base that only slightly dissociates in water e.g. NH3 |
| what is the equilibrium of water? | H2O -> H+ + OH- |
| what is Kw? | Kw= [H+][OH-] units: mol2dm-6 |
| what is Kw in pure water? | Kw in pure water= [H+]^2 because [H+]=[OH-] |
| what is the equation for pH and [H+]? | pH=-log[H+] [H+]=10^-pH |
| how to calculate pH of strong acids? | monoprotic: [H+]=[acid] diprotic: [H+]=2 x [acid] |
| how to calculate the pH of strong bases? | [H+]= Kw / [OH-] remember that [OH-] may be x2 if diprotic |
| what is the acid dissociation constant (Ka) where weak acid and salt are present? | Ka= [H+][A-] / [HA] where A- is salt and HA is weak acid units: moldm-3 |
| what is Ka when only weak acid present? | Ka= [H+]^2 / [HA] |
| how to calculate pH of weak acid? | use Ka equation, change it depending on whether salt is also present to find [H+] then calculate pH using "-log[H+]" |
| what is pKa and how to find Ka from it? | pKa=-log(Ka) Ka=10^-pKa |
| explain the pH curves for: strong a strong b strong a weak b weak a strong b weak a strong b and state the indicator used for each | sA/sB: 1--13 any sA/wB: 1--9 methyl orange wA/sB: 5--13 phenolphthalein wA/wB: 5--9 none |
| what are the colours of the 2 indicators at low pH and high pH? | methyl orange: LOW=red HIGH=yellow phenolphthalein: LOW=colourless HIGH=pink |
| where is the equivalence point? | the midpoint of the vertical part of the pH curve--drawing a line down to the x axis at this point will state the volume needed to neutralise the acid/alkali |
| how to calculate the conc of something in a titration/neutralisation? | write out a balanced equation calculate any moles you can find conc: moles of thing neutralising / total volume |
| what do you get when you neutralise a diprotic weak acid with a strong base? | 2 equivalence points, as 2 H+ ions are being released separately |
| how to calculate conc of diprotic acid from titration results? | write a balanced equation find what u know & what u need to know calculate moles of base use ratio to find moles of acid find conc of acid: moles / volume |
| what is a buffer solution? | a solution that resists change to pH when small amount of acid or alkali are added |
| what is an acidic buffer? | weak acid and its salt if you add acid, [H+] increases, combining with salt ions to form more acid so equilibrium shifts to left. if you add base, [OH-] increases, reacting with [H+] to form water so equilibrium shifts to right. |
| what is a basic buffer? | made from weak base and its salt if base is added, [OH-] increases, reacting with ions so equillibrium shifts left. if acid is added, [H+] increases, reacting with base so equilibrium shifts right. |
| how to calculate pH of buffer solution? | write expression for Ka enter what you know rearrange for [H+] use pH=-log[H+] |
| give some uses of buffers | shampoo biological washing powder soap |
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