What happens when bonds are broken?
Energy goes in from the surroundings ∴ endothermic
What happens when bonds are created?
Energy goes out into surroundings ∴ exothermic
What is the activation energy? How does a catalyst affect this?
It is the minimal energy required for a reaction to take place. A catalyst provides another route for the reaction with a lower activation energy
How do you calculate energy change?
Break - make
What type of reaction is delta H-?
Exothermic- as H stands for enthalpy(chemical energy) and the reaction overall loses enthalpy to the outside world
What type of reaction is delta H +?
Endothermic- as H stands for enthalpy(chemical energy) and the reaction overall gains more enthalpy from the outside world
How do you measure the energy given out using a bomb calorimeter?
• measure temp and volume of water before
• measure mass of sample
• burn sample
• measure temp of water. Calculate change
E(energy) = M(mass) x C(specific heat capacity) X change in T(temp)
What is equilibrium?
When the rate that A+B is reacting to make C+D is the same as the rate of C+D making A+B, and it stays there
What is the reaction with ammonium chloride?
ammonium chloride ⇌ ammonia + hydrogen chloride Ammonium chloride (a white solid) breaks down to ammonia and hydrogen chloride. It also shows that ammonia and hydrogen chloride (colourless gases) can react to form ammonium chloride again
What is the reaction with anhydrous copper sulphate?
Anhydrous copper(II) sulfate + water ⇌ hydrated copper(II) sulphate
What does the number at the end of the equation show?
If positive: forwards equation is endothermic, as heat energy goes in
If negative: forwards equation is exothermic, as heat energy goes out
What is le chatelier’s principle?
If conditions of equilibrium changed, equlibirum will move to oppose the change(Only for gases do)
How does changing the concentration affect the equilibrium?
The equilibrium will want to use up all that substance, so lots of that reaction will happen ∴ more off the products on the other side will be made
How does changing the temperature affect the equilibrium?
If surrounding temp is raised: will shift towards endothermic reaction, to use up the energy
If surrounding temp was lowered: would shift towards exothermic reaction, to increase surrounding temp
How does changing the pressure affect the equilibrium?
If raised: will shift to side with fewest molecules
If lowered: will shift to side with most molecules
If same number of molecules, equilibrium can’t change
What are example of exo/endo reactions?
Exo: firework exploding, burning
Endo: kettle boiling, ice melting
What is dynamic equilibrium?
When the forwards and backwards reaction happen at the same rate and same time. The concs of prods/reactants remain constant.