Chemical reactions are reversible and may reach a dynamic equilibrium.
The position of equilibrium of a reversible reaction can be altered by changing the reaction conditions.
Reversible reactions involve products that can react together to produce the original reactants.
These reactions are called reversible reactions.
Reversible reactions can be represented in the following way: A + B ⇌ C + D.
Reversible reactions can be represented in equations: the forward reaction is the one that goes to the right and the backward reaction is the one that goes to the left.
The reaction mixture may contain reactants and products, and their proportions may be changed by altering the reaction conditions.
Ammonium chloride is a white solid that breaks down when heated, forming ammonia and hydrogen chloride.
The balanced chemical equation for the breakdown of ammonium chloride is: NH 4 Cl(s) ⇌ NH 3 (g) + HCl(g).
If a reaction is exothermic, it will give out energy to the surroundings, increasing the temperature.
If a reaction is endothermic, it will take in energy from the surroundings, decreasing the temperature.
The same amount of energy is transferred in both the forwards and reverse reaction.
Blue copper sulfate is described as hydrated copper sulfate, containing water of crystallisation, which can be removed by heating strongly.
A copper ion is an electrically charged particle, formed when an atom or molecule gains or loses electrons in its crystal lattice.
The crystal lattice is the regular arrangement of particles (atoms, molecules or ions) in a crystal.
A molecule is a collection of two or more atoms held together by chemical bonds.
Water is driven off when blue hydrated copper sulfate is heated, leaving white anhydrous copper sulfate.
The reaction of hydrated copper sulfate with water is reversible: hydrated copper sulfate ⇌ anhydrous copper sulfate + water.
The forward reaction of hydrated copper sulfate with water is endothermic and the reverse reaction is exothermic.
When a reversible reaction happens in a closed container, it reaches a dynamic equilibrium.
In chemical reactions, a situation where the forward and backward reactions happen at the same rate, and the concentrations of the substances stay the same.
At equilibrium: the forward and backward reactions are still happening the forward and backward reactions have the same rate of reaction the concentrations of all the reacting substances remain constant.
Nitrogen reacts with hydrogen to produce ammonia: N 2 (g) + 3H 2 (g) ⇌ 2NH 3 (g).
The balanced equation for the backward reaction of nitrogen reacting with hydrogen is 2NH 3 (g) → N 2 (g) + 3H 2 (g).
Changing the position of equilibrium in a chemical reaction can be done by changing the concentration, temperature, or pH.
Rates of reaction are important in understanding the rate and extent of chemical change.
AQA offers sample exam questions on the rate and extent of chemical change.
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