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79 Cards in this Set
- Front
- Back
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What is a Bronstead-Lowry acid? |
A proton donor |
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What is a Bronstead-Lowry base? |
A proton acceptor |
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What is a monobasic acid? |
An acid which can release one proton per molecule when it dissociates in water and requires 1 mole of OH- to neutralise it. |
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What can a monobasic acid also be called? |
A monoprotic acid |
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What is a diprotic acid? |
An acid which can release two protons per molecule when it dissociates in water and requires 2 moles of OH- to neutralise it.
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What is a tribasic acid? |
An acid which can release three protons per molecule when it dissociates in water and requires 3 moles of OH- to neutralise it.
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What is the ionic formula for neutralisation? |
H+ + OH- --> H2O |
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What is a salt? |
A compound produced when a H+ ion from an acid is replaced by a metal ion or other positive ion e.g. NH4 |
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What is produced when a metal reacts with an acid? |
A salt and hydrogen |
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What is the ionic equation? |
Metal + 2H+ ---> Metal ion + H2 |
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What type of reaction is this? |
Redox |
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What is produced when you react an acid and a metal oxide? |
Salt and water |
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What is the ionic equation for this? |
O2- + 2H+ --> H2O |
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What type of reaction is this? |
Neutralisation |
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What is produced when you react an acid with an alkali? |
A salt and water |
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What is the ionic equation for this? |
OH- + H+ --> H2O |
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What type of reaction is this? |
Neutralisation |
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What do you get when you react an acid with a metal carbonate? |
A salt, CO2 and water |
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What is the ionic equation for this? |
CO3 2- + 2H+ --> CO2 + H2O |
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What type of reaction is this? |
Neutralisation |
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What is produced when you react ammonia with acid? |
An ammonium salt |
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What is the ionic equation for this? |
NH3 + H+ --> NH4+ |
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What type of reaction is this? |
Neutralisation |
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What happens when an acid is added to water?
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A proton is released |
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When is an acid and acid? |
When it's aqueous |
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What is a strong acid? |
A proton donor which completely dissociates into its ions in aqueous solution (irreversible) |
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What is a weak acid?` |
A proton donor that only partially dissociates into its ions in aqueous solution (reversible) |
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What happens when HCl(g) is dissolved in water? |
The H-Cl bond breaks and we say the acid has dissociated into its ions |
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What happens to the proton( H+) that is released? |
It is accepted by water to form an oxonium ion, H3O+ |
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What is a conjugate acid-base pair? |
A pair of two species that transform into each other by the gain or loss of a proton (H+) |
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What is an example of this? |
HCl + H20 <--> H3O+ + Cl- Acid 1 Base 2 Acid 2 Base 1 |
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What is the same in each conjugate acid-base pair? |
The acid and base in the pair differ by a proton The species richer in protons acts as the acid |
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What is another example of a conjugate acid-base pair? |
HNO3 + H2SO4 --> H2NO3+ + HSO4- Base 1 Acid 2 Acid 1 Base 2 |
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What decides which acid acts as the acid? |
The stronger acid acts as the acid |
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What are 2 examples of strong bases? |
NaOH KOH |
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What are two example of weak bases? |
Ammonia NH3 + H2O -->NH4+ + OH- Amines (RNH2) |
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What happens to strong acids when they dissociate?
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Equilibrium position is so far to the right that the reverse reaction is insignificant. Dissociation is complete (only forward reaction takes place) Concentration of protons (H+) is high |
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What happens when weak acids dissociate? |
Equilibrium position is far to the left and the reverse reaction is significant. Dissociation is partial ( incomplete forwards reaction) Concentration of protons (H+) is low compared with the concentration of undissociated acid |
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What is Ka? |
The acid dissociation constant |
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How do you work out Ka? |
[H+] [A-]/ [HA] |
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What does Ka indicate? |
The extent (degree) of acid dissociation |
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What does it mean if Ka is large? |
[H+] and [A-] are large Equilibrium position is far to the right A lot of the HA acid is dissociated into its ions ( suggests a strong acid) |
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What does it mean is Ka is small? |
[H+] and [A-] are small Equilibrium position is far to the left A lot of the HA acid is not dissociated (suggests a weak acid) |
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What is the strongest acid and why? |
HCl as it has the largest Ka value and is most dissociated into its ions in solution |
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What is the issue with Ka values? |
They can be very large or very small and as a result, are difficult to use |
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What do we do to combat this? |
We use pKa values instead |
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How do we work out pKa? |
-log Ka |
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How do you convert pKa back to Ka? |
Ka= 10^-pKa |
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What does Ka depend on? |
Temperature only |
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What is Kw? |
The ionic product of water |
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What does pure water do? |
Pure water ionises ( dissociates) however the extent of dissociation is very small |
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What is one of the equations for this? |
H20 <--> H+ + OH- |
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What is another equation for this? |
H2O +H2O <--> H3O+ + OH- |
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What is this reaction known as? |
Self dissociation or self ionisation of water |
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What type of equilibrium is this an example of? |
Heterogeneous equilibrium |
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What is the equation for Kw? |
Kw= [H+] [OH-] |
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Why is H2O left out? |
It's considered constant for ionic equilibria |
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What does Kw depend on? |
Temperature |
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What is the equation to work out pH? |
pH= -log [H+] |
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What does a low pH mean? |
A high [H+] concentration |
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What does a high pH mean? |
A low [H+] |
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What is the scale described as? |
Logarithmic, values go up by a factor of 10 |
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How can you convert pH back to [H+]? |
[H+]= 10^-pH |
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What should pH values be recorded to? |
An appropriate number of decimal places- should equal to number of significant figures for the concentration data
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Why is Kw important is all aqueous solutions? |
H+ and OH- will always be present such that [H+] [OH-] =Kw |
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What is true for acidic solutions? |
[H+] > [OH-] |
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What is true for neutral solutions? |
[H+] = [OH-] |
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What is true for basic solutions? |
[H+] < [OH-] |
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What can be changed in the equation if you're working out Kw for a neutral solution? |
Kw= [H+] [OH-] and [H+]=[OH-] therefore Kw= [H+][H+] therefore Kw=[H+]^2 |
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What happens in a strong acid? |
It completely dissociates |
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What can we write for a strong monobasic acid? |
[HA] = [H+] |
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What happens in a weak acid? |
It only partially dissociates so in order for us to work out pH, we have to make a few assumptions |
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What are these assumptions? |
A large proportion of the acid remains undissociated so we an assume [HA] equilibrium~[HA] undissociated Due to negligible dissociation of water in the solution, we can assume that [H+]~[A-] |
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Due to the assumptions, what are the limitations to these approximations? |
'Stronger' weak acids will have a larger Ka value and a greater degree of dissociation, therefore our assumption of [HA] equilibrium~[HA] undissociated may no longer be valid |
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What other limitation is there? |
'Weaker' (or very dilute) weak acids will have a very low [H+], meaning that the [H+] from the self dissociation of water will be significant. Hence, our assumption that [H+] ~ [A-] may no longer be valid |
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What is a strong base? |
An alkali that completely dissociates into hydroxide ions |
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How do we work out pH for a strong base? |
using molar ration, [metal OH] = [OH-] Use Kw= [H+][OH-] Find [H+] Use this to find pH |
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What can Kw=[H+][OH-] also be expressed as? |
pKw= pH+pOH |
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What is another method to find pH of a strong base? |
Use the alternative formula Find pOH Then find pH |
