Energy Changes and ROR

Created by

Charlotte Dredge

Cards (25)

What is an endothermic reaction?
An endothermic reaction is a chemical reaction that absorbs heat from its surroundings, resulting in a decrease in temperature.
What is an exothermic reaction?
An exothermic reaction is a chemical reaction that releases heat to its surroundings.
What is the name of the energy required to start a reaction?
Activation energy
Is breaking bonds endo- or exothermic?
Endothermic (energy in)
Is forming bonds endo- or exothermic?
Exothermic (energy released)
How does a catalyst speed up a reaction?
It provides an alternate reaction pathway that has a lower activation energy
What is bond energy?
Bond energy is the amount of energy required to break 1 mole (6 $\times$ 10 $^{23}$ bonds) of a given type of bond
What is overall energy change?
The difference between the energy needed to break the bonds in the reactants, and the energy given out when new bonds are made in the products.
How do you work out the mean rate of reaction? (2 equations)
quantity of reactant used/time taken
quantity of product made/time taken
What observations can be made to show a reaction has taken place?
Color change, gas production, precipitate formation, temperature change, reactant used up
What factors affect rate of reaction?
Temperature
Concentration or pressure
Surface area
Catalyst
Why does an increase in temperature increase rate?
particles move faster = more frequent collisions
particles have more energy = higher success rate of collisions
Why does increased concentration or pressure increase rate?
more particles present = increased chance of collisions
Why does increased surface area increase rate?
increased surface area = more particles able to collide
Why does a catalyst increase rate of reaction?
the activation energy is reduced so collisions are more frequently successful
What is a reversible reaction?
A reaction that can proceed in both the forward and reverse directions.
What is dynamic equilibrium?
A state where the rate of the forward and backward reactions is equal
What is Le Chatilier's Principle?
If a dynamic equilibrium is disturbed by changing the conditions the position of equilibrium moves to counteract the change.
If the reaction $N_2O_4(g)\ \leftrightarrow\ 2NO_2(g)$ was put under high pressure which side would the position of equilibrium favour? 
The left because the position favours the side with the fewest gas particles under high pressure.
If the temperature is increased, would the position of equilibrium favour the endothermic or the exothermic reaction?
Endothermic
What are the conditions used in the Haber process?
$450^{\circ}$
200 atmospheres
Why are the conditions for the Haber process used?
It is a compromise because it balances rate, yield and cost.
Low temp = high yield + low rate
What are the steps of the Haber process?
Extract $N_2$ from the air
Make $H_2$ from natural gas
Pass over $Fe$ catalyst at 450 degrees and 200 atmospheres
Liquefy and remove the ammonia
Recycle unreacted $N_2$ and $H_2$
Does a catalyst change the position of equilibrium?
No because it lowers the activation energy for both the forward and backwards reactions
What are NPK fertilisers?
Fertilisers containing Nitrogen, Phosphorus, and Potassium