2.1 Chemical equilibrium and acid-base reactions

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What is dynamic equilibrium?
a system is in dynamic equilibrium when the forward and reverse reactions occur at the same rate
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State Le Chatelier's principle
states that a system at equilibrium is subjected to change the equilibrium tends to shift so as to minimise the effect of the change
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What is a reversible reaction?
A reaction in which the reaction can take place in both forward and backward directions
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*1 Explain the term dynamic equilibrium for a chemical system.
An equilibrium system where the forward and reverse reactions occur at the same rate
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Name three factors that can affect the position of equilibrium?
- Changing concentration of reactants or products - Change in pressure reactions involving gases - Changing temperature
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How does a catalyst affect the position of equilibrium?
It does not affect the position of equilibrium however equilibrium is reached quicker
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How does increasing the concentration affect the position of equilibrium?
Equilibrium will shift to side of reaction giving less acidity/H+
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How does decreasing the concentration affect the position of equilibrium?
Equilibrium will shift to side of reaction giving more acidity/H+
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How does decreasing the temperature affect the position of equilibrium?
Equilibrium will shift to the side of the reaction that is exothermic
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How does increasing the temperature affect the position of equilibrium?
Equilibrium will shift to the side of the reaction that is endothermic
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How does decreasing the pressure affect the position of equilibrium?
Equilibrium will shift to the side of the reaction that contains more moles of gaseous atoms
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How does increasing the pressure affect the position of equilibrium?
Equilibrium will shift to the side of the reaction that contains less moles of gaseous atoms
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Define an acid
A proton (H+) ion
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Define a base
A proton (H+) acceptor
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*2 Write down the formulae for the following: (a) sulfuric acid (b) ammonia (c) potassium hydroxide
(a) H2S04 (b) NH3 (c) KOH
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What happens when an acid is put into water?
A H+ dissociates
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What happens when a base is put into water?
OH- dissociates
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What are the pH values of acids?
less than 7
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What are the pH values of bases/alkalis?
greater than 7
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What is the pH value of neutral solutions?
7
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What does carbon dioxide form when in reacts with water?
Carbonic acid
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What is the reversible equation for carbon dioxide in water?
CO2 + H2O reversible arrow H2CO3
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Why is rainwater acidic?
Because CO2 in the air has dissolved in the water
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What happens when acidic rainwater flows over the ground containing calcium carbonate (limestone)?
Converts to Ca(HC03)2 (aq) or hydrogencarbonate and so eroding the original limestone
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*3 By considering its interaction with water, explain how carbon dioxide can behave as an acid.
It forms an H+ ion
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What is a buffer solution?
A solution that resists a change in pH when contaminated with small amounts of acid or alkali
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Write the equilibrium equation for carbon dioxide and sea water
H2O + CO2 H+ HCO3
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What information can you discover about unknown solution in titration
- Concentration of solution - molar mass - its formula - the percentage of substance
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Name the four steps to prepare a standard solution from a solid
1, accurately weigh required mass of solid, 2, transfer all of solid into beaker and add water and stir until all solid dissolved, 3, pour solution into volumetric flask add water to just below mark, 4, add water drop by drop to mark and mix well
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*4 20cm3 of aqueous sodium hydroxide was exactly neutralised by 16cm3 of 0.250 mol dm-3 aqueous hydrochloric acid solution, Calculate conc. of sodium hydroxide. NaOH + HCl -> NaCl H2O
0.2 mol dm-3
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Card 2

Front

State Le Chatelier's principle

Back

states that a system at equilibrium is subjected to change the equilibrium tends to shift so as to minimise the effect of the change

Card 3

Front

What is a reversible reaction?

Back

Preview of the front of card 3

Card 4

Front

*1 Explain the term dynamic equilibrium for a chemical system.

Back

Preview of the front of card 4

Card 5

Front

Name three factors that can affect the position of equilibrium?

Back

Preview of the front of card 5
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