Energy And Equlibrium Flashcards
What happens when bonds are broken?
Energy is taken is in
What happens when bonds are formed?
Heat energy is given out
What is an exothermic reaction?
A chemical reaction that gives out heat energy
What is an endothermic reaction?
A chemical reaction that takes in heat energy
Examples of exothermic reactions are?
Neutralisation
Combustion
Displacement reactions
Dissolving
Hydration
Examples of endothermic reactions are?
Thermal decomposition
Photosynthesis
Dissolving
Electrolysis
Thermal cracking of hydrocarbons
Explain how the energy within an exothermic reaction changes as the reaction progresses and how it looks on a graph.
Look in book
The products are below the reactants as they have less energy
Explain how the energy within an endothermic reaction changes as the reaction progresses and how it looks on a graph.
Look in book
The Products are above the reactants as they have more energy
How do you calculate energy change in a chemical reaction?
Energy change = Energy taken in to break bonds - Energy released when new bonds are formed
What is the definition of reversible?
A reaction which goes in both the forward and backward directions
What is the definition of dynamic equilibrium?
The rate of the forward reaction is equal to the rate of the backward reaction
The amounts of reactant and product remain constant
What is the definition of homogeneous?
A reaction in which all the reactants and produce that are produced are in the same physical state
What is Le Chatlier’s principle?
If a dynamic equilibrium is distributed by changing the conditions, the position of equilibrium moves to counteract the change.
What is the affects of changing the pressure in a closed homogenous system?
To increase the pressure, the position of the equlibrium moves to the side with the most gas molecules.
To decrease the pressure, the position of the equlibrium moves to the side with the least gas molecules.
What are the affects of changing the pressure in a closed homogeneous system?
To increase the pressure, the position of the equilibrium moves to the side with the most gas molecules and vice versa to decrease the pressure
What are the affects of changing the temperature in a closed homogeneous system?
Increasing the temperature of a system in dynamic equilibrium favours the endothermic reaction as it counteracts the change by absorbing more heat
Decreasing the temperature of a system in dynamic equilibrium favours the exothermic reaction as it counteracts the change by producing more heat
What is a closed system?
Where no substances can get in or out
What is the Haber process?
Combines nitrogen from the air with hydrogen derived mainly from natural gas (methane) into ammonia.
The reaction is reversible and exothermic
What are the industrial conditions for the haber process?
- 200 atmospheres of pressure
- 450 degrees centigrade
- Iron catalyst
What are the raw materials for the haber process?
Hydrogen - obtained by reacting natural gas (methane) with steam, or through the cracking of oil
Nitrogen - Obtained by burning hydrogen in air
How is nitrogen obtained?
Air is 78% nitrogen nearly all the rest is oxygen. When hydrogen is burned in air the oxygen combines with hydrogen, leaving nitrogen behind.
How is hydrogen obtained?
Obtained by reacting natural gas (methane) with steam, or through the cracking of oil
What does methane + steam produce?
Carbon monoxide + Hydrogen
What is the word equation for the Haber process and the symbol equation?
Nitrogen + Hydrogen —–> Ammonia
N2 (g) + 3H2 (g) ——> 2NH3 (g)
What is the effect if pressure on the Haber process?
A high pressure would move the equilibrium to the right where there are fewer molecules, increasing the yield of ammonia produced.
What are the problems with maintaining a high pressure?
- Extremely strong pipes and containment vessels must be built
- Costs a lot to produce and maintain
What is the effect if a catalyst on the Haber process?
The iron catalyst has no effect on the position of the equilibrium, It only speeds up the rate of reaction.
What is the effect of temperature on the Haber process?
The forward reaction is exothermic and this will be favoured by decreasing the temperature.
To get a higher yield of ammonia, you need a lower temp but the lower temp you use the slower the rate of reaction.
What is a good compromise for pressure and temperature during the Haber process.
- 200 Atmospheres of pressure
- 400-450 Degrees Celsius
What is the composition of air, lil bro?
- 78% Nitrogen
- 21% Oxygen
- Average surface temp - 20 Degrees
- Traces of CO2, Water Vapour, Ammonia & Methane
Describe a nitrogen molecule?
- Diatomic molecule
- Triple covalent bond
What are the properties of nitrogen?
- Colourless gas
- Odourless gas
- Insoluble in water
- Diatomic
What are the uses of nitrogen?
- Coolant
- Food Packaging
- Manufacturing Ammonia
What are the properties of ammonia?
- Colourless gas
- Choking smell
- Weak Alkali
- Very Soluble in Water
What is ammonia?
NH3 is a compound of nitrogen and hydrogen
What are the uses of ammonia?
- Fertilisers
- Nitric Acid
- Manufacture of Nylon
What is the test for ammonia?
Hold a glass rod dipped in concentrated HCL near the gas
If ammonia is present a white smoke is formed
Ammonia + Hydrogen Chloride —–> Ammonium Chloride
Explain for 5 marls how to tell whether a reaction is endothermic or exothermic?
When thee reactant bonds are broken energy is take n in, this is an endothermic reaction.
When the products bonds are formed energy is given out, this is a exothermic reaction
Whether more energy is taken in or given out tells you if it is exothermic or endothermic.
