Chemistry /PH and Indicators Flashcards Part 2
What is the pH of an indicator?
Indicators themselves are weak acids or weak bases and dissociate in solution.
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Term
Definition
What is the pH of an indicator?
Indicators themselves are weak acids or weak bases and dissociate in solution.
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HIn is an indicator that is itself a weak acid, Write a balanced equation to represent the dissociation of HIn in water/solution.
Hln + H2O ⇌ ln- + H3O+
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HIn is an indicator that is itself a weak acid. Place the indicator in an acid.
Concentration of H3O+ increases, the equilibrium shifts to decrease concentration of H3O+ to the left to use it up. Reverse reaction favoured, colour ...
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HIn is an indicator that is itself a weak acid. Place the indicator in a base.
Concentration of OH- increases, they will react with the H3O- ions to form H2O. Concentration of H3O+ decreases, equilibrium shifts to increase concen...
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XOH is an indicator that is itself a weak base. Write a balanced equation to represent the dissociation of XOH in water / solution.
XOH ⇌ X+ + OH-
XOH is an indicator that is itself a weak base. Place the indicator in an acid.
Concentration of H+ increases - they will react with OH- ions to form H2O. Concentration of OH- decreases. Equilibrium shifts to increase concentratio...
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| Term | Definition |
|---|---|
What is the pH of an indicator? | Indicators themselves are weak acids or weak bases and dissociate in solution. |
HIn is an indicator that is itself a weak acid, Write a balanced equation to represent the dissociation of HIn in water/solution. | Hln + H2O ⇌ ln- + H3O+ |
HIn is an indicator that is itself a weak acid. Place the indicator in an acid. | Concentration of H3O+ increases, the equilibrium shifts to decrease concentration of H3O+ to the left to use it up. Reverse reaction favoured, colour A (left hand side) due to increased concentration of Hln. |
HIn is an indicator that is itself a weak acid. Place the indicator in a base. | Concentration of OH- increases, they will react with the H3O- ions to form H2O. Concentration of H3O+ decreases, equilibrium shifts to increase concentration of H3O to produce more of it. Forward reaction favoured to the right. Colour B forms (RHS) to increase the concentration of ln-. |
XOH is an indicator that is itself a weak base. Write a balanced equation to represent the dissociation of XOH in water / solution. | XOH ⇌ X+ + OH- |
XOH is an indicator that is itself a weak base. Place the indicator in an acid. | Concentration of H+ increases - they will react with OH- ions to form H2O. Concentration of OH- decreases. Equilibrium shifts to increase concentration of OH- to produce more of it. Forward reaction favored to the right. Colour B forms due to increased concentration of OH- (RHS). |
XOH is an indicator that is itself a weak base. Place the indicator in a base. | Concentration of OH- increases. Equilibrium shifts to decrease conc of OH-, to the left to use it up. The reverse reaction is favoured, Colour A forms due to increased conc of XOH. |
What is a pH titration? | An acid base titration where a pH meter is placed in the acid in a beaker. ALL OF THE BASE is added. Changes in PH are recorded. A pH curve is plotted. The Endpoint can be found from the vertical part of the graph. Endpoint is the volume of base required for neutralisation. |
In pH titrations, why is a beaker used instead of a conical flask? | A beaker is more suitable to place the pH meter probe and stir. |
In pH titrations, why is the acid in a beaker and base in a burette? | Allows us to start with a low pH value and work upwards. |
In pH titrations, why is an indicator not required? | pH is directly measured by pH meter. |
Describe a pH titration between a strong acid and a strong base, and list a potential indicator and explain. | End point between 3 -11, The vertical part of the titration is the volume of base required for neutralisation. Methyl orange or Phenolphthalein, the vertical part of the titration- end point between pH 3-11. Methyl orange or Phenolphthalein changes colour according to the vertical part of the graph. |
Describe a pH titration between a strong acid and a weak base and list a potential indicator and explain. | The end point is between pH 3-7. A potential indicator is methyl orange. The vertical part of the titration is the volume of base required for neutralisation. Shown by the vertical part. The end point is between 3-7, Methyl orange changes colour according to the vertical part of the graph. |
Describe a pH titration between a weak acid and a strong base and a potential indicator, explain. | The end point is between pH 7-11. Potential indicator is phenolphthalein. The vertical part of the titration is the volume of base required for neutralisation. As shown by the vertical graph- the end point occurs between a PH of 7-11. Phenolphthalein changes colour coinciding with the vertical part of the graph. |
What is the formula for Vb? | Ma x Va / na = Mb x Vb / nB |
Write an equation for the dissociation of water. | 2H2O ⇌ H3O+ + OH- |
What is the only thing that affects Kw? | Temperature |
Is the self ionisation of water endothermic or exothermic, explain. | As the temperature increases, Kw increases. Equilibrium shifts to decrease temperature in the endothermic direction. Kw: the forward reaction is favoured. The forward reaction is endothermic, the self ionisation of water is endothermic. |
What is unique about pure water? | [H3O+]=[OH-] |