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Dynamic equilibria, chemical cells and fuel cells GapFill
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A system in dynamic equilibrium, such as the reversible reaction to form ammonia from hydrogen and nitrogen in the process, will act to minimise a change in conditions.
- If the concentration of a reactant or product is changed, the of all the substances will change until the reaction is at equilibrium again.
- If the temperature of the system is changed, the rate of the forward and backward reactions will change until equilibrium is reached. temperatures favour endothermic reactions, and temperatures favour exothermic reactions.
- For reactions with gaseous reactants, the pressure can affect the position of equilibrium. High pressures shift the position of equilibrium to the side with fewer molecules.
- Catalysts do not change the position of equilibrium, but will speed up the rate at which it is reached.
An chemical cell produces a voltage until the chemicals are .
Fuel cells use a fuel such as hydrogen. They also take in from the air. In these cells, hydrogen is to form as the only product. This reaction produces . The half-equations for an electrochemical cell are:
- Cathode: H2 (g) → (aq) + 2e⁻
- Anode: 4H⁺ (aq) + O2 (g) + → 2H2O (l)