Flashcards
Acid and bases
Cards in this deck (37)
- 1What is bronsted-lowry acid?Proton donor
- 2What is bronsted-lowry base?Proton acceptor
- 3What type of reaction is acid base equilibria?Neutralisation
- 4What does acid base equilibria involve?Proton transfer
- 5Define pH.pH = – log10[H+]
- 6What do the brackets represent?The concentration
- 7What are the units of concentration?mol dm-3
- 8How do you convert concentration into pH?[H+] = 10^-pH
- 9How do you calculate the pH of a solution of a strong acid from its concentration?pH = – log10[concentration of solution]
- 10What is a strong acid?Fully ionised in water
- 11How do you calculate the pH for a strong monoprotic acid?pH = – log10[concentration]
- 12How do you calculate the pH for a strong diprotic acid?pH = – log10[2x concentration]
- 13How do you calculate the new pH of a strong acid when added to water?[ H+]new = [ H+]old x old volume/new volume
- 14What is water?weakly disociated
- 15What equation do you use to work out the Kw (ionic product of water) ?Kw = [H+][OH– ]
- 16How do you calculate the pH of a strong base from its concentration?Kw=[H+] [OH-]
- 17What is a strong base?Fully ionised in solution
- 18How do you work out the pH of a monobasic base?[OH-]= [base]
- 19How do you work out the pH of a dibasic base?[OH-]= [2x base]
- 20How do you work out the pH of a diluted strong base?[ OH-]new = [ OH-]old x old volume/new volume
- 21What steps do you use to work out the pH for the reaction between a strong acid and strong base?1. Calculate moles of H+
2. Calculate moles of OH-
3. Calculate moles excess H= or OH-
4. Calculate excess [ H+] or excess [ OH-]
5. Calculate pH - 22What do weak acid and bases do in water?Partially dissociate
- 23What is the expression for the dissociation constant Ka for a weak acid?Ka= [ H+]2/[ HA]
- 24Define pKa.pKa = – log10 Ka
- 25What is the equivalence point for a reaction between a strong acid and strong base? What indicator should be used?7
Any indicator can be used. - 26What is the equivalence point for a reaction between a strong acid and weak base? What indicator should be used?5
Methyl orange - 27What is the equivalence point for a reaction between a weak acid and strong base? What indicator should be used?9
Phenolphthalein - 28What is the equivalence point for a reaction between a weak acid and weak base? What indicator should be used?equivalence point can not be accurately detected.
Use a pH probe - 29Why can the equivalence point can not be accurately detected in the reaction between a weak acid and weak base?The variation in the pH is so gradual.
- 30what are indicators?Weak organic acids
- 31Define Buffer.A solution whose pH is resistant to change on the addition of small quantities of acid or base.
- 32What happens to an acidic buffer if acid is added?H+ combines with A- to from HA.
The equilibrium moves to the left to remove the H+.
As long as reservoir of A- large enough all the H+ can be removed and the pH is unchanged. - 33What happens to an acidic buffer if base is added?OH- combines with H+ to form H2O. This reduces concentration of H+ so more HA will dissociate to replace the H+.
Equilibrium will move to the right.
As long as reservoir of HA is large enough, all the H+ can be replaced and the pH is unchanged. - 34What happens to an Basic buffer if acid is added?Ammonia acts as a sink and mops up proton to form ammonium ions. Equilibrium shifts to the right and as long as there is sufficient NH3 the pH will remain unchanged.
- 35What happens to an Basic buffer if base is added?Ammonium ions act ac a source of H+ ions and remove the OH- to reform ammonia.
Equilibrium shifts to the left and as long as there is sufficient NH4+ the pH will remain unchanged. - 36How do you calculate the pH of acidic buffer?[H+] = Ka x [HA]/ [A-]
Then use: -log10(H+) - 37What are examples of buffers?Organic acids like methanoic acid etc.
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- A Levels Chemistry (Unit 4) Flashcards on Acid and bases, created by megan.radcliffe16 on 17/12/2014.
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