Chemical rates & energetics Flashcards
Collision theory
Define chemical reaction
Making of new products from the rearrangement of reactants
Define rate of reaction
How quickly a reactant is used up or how quickly product is formed
Define high rate of reaction
Reactants turn into products quickly
Define low rate of reaction
Reactants turn into products slowly
What particles need to collide [2]
1) In correct orientation
2) Enough energy
Define successful collisions
When reactant particles collide and turn into products.
Define activation energy
Smallest amount of energy required for reaction to occur
What is a reactant
What you start with in a reaction
What is a product
What you end with in a reaction
How does the amount of reactant particles change throughout a reaction? [3]
1) Lots of reactant particles at the beginning, steep line due to lots of reactions
2) Rate of reaction slows down as there is now a mixture of reactant and products particles
3) The reactions are finished line is flat and theres only product particles with no reactant particles.
Mean rate of reaction formula (g/s)
Mass (g) /time taken (s)
Mean rate of reaction formula (cm3/s)
Volume (cm3) / time taken (s)
How is gas collected?
A gas syringe
What does it mean if gas is collected quickly
Rate of reaction is high
Define concentration
Quantity of subtance in a set volume
Explain the effect that increasing the concentration of something has on the rate of reaction
1) Higher concentration means high rates of reaction
2) More particles in the same space due to higher concentration
3) more frequent collisions means more successful collisions
Increasing temperature increases both
1) Frequency of collisons
2) The number of collisions with enough energy to react
Factors effectig rate of reaction [7]
1) Concentration, increase amount of particles
2) Pressure, increase gas particles
3) Reduce volume, less distance
4) Temperature, increase kinetic energy of particles
5) Surface area more particles are exposed on the outside
6) Catalyst will lower the activation energy
7) Biological catalyst dont denature in chemistry
What 2 things happen when chemical reaction takes place
1)New products- chemical change
2) Change in heat energy
How to break bonds
Energy is absorbed
How to form bonds
Energy is released
Endothermic reactions definition
Energy is absorbed from the surroundings, the temperature of the surroundings decrease. It gets colder to convert thermal into chemical energy to break bonds
Exothermic reactions definition
Heat energy is produced, temperature of the sourroundings increases
More energy is released compaired to the energy…
More energy is released compaired to the energy needed to breakt the catalyst
Compare the speeds of radio waves and visible light in a vacuum:
Radio waves and visible light have the same speed in a vacuum because all EM waves travel at the speed of light
What are bonds?
C = C, H - H
they are lines between molecules
How to calculate number of bonds of H - O - H
H - O - H
2 bonds
Does O = c = O count as 4 bonds
FALSEE!!!
It is a covalent double bond so its still 1 bond
In total it has 2 bonds
Law of break and making bond
Energy required to break bond is equal to energy required to make bond
Overall energy change formula
Energy needed to break the bonds (reactant) - energy released as bonds are made (products)
Explain successful and unsuccessful collisions
1) Successful means that the reactant particles collide and rearrange to form the products
2) Unsuccessful means the reactant particles just bounce off each other and remain unchanged
Enthalpy change (ΔH)
= Energy taken in - Energy given out
Define enthaply
a measure of the total heat of reaction of a chemical reaction
Reversible reaction definition
Means the reaction goes back and forth constantly
Define equilibrium
Forward and backward reaction are taking place at the same rate at the same time
Define closed system
No substance can enter or exit
Le Chatelier principle
If a change is made to the conditions of the system at equilibrium, then the position of the equilibrium moves to oppose that change in conditions
(If u make the system hot it doesnt like it and trys to cool)
Equilibrium lies to the left
More reactants than products in the mixture of chemicals
Equilibrium lies to the right
More products than reactants in the mixture of chemicals
Define catalyst [2]
1) A substance that speeds up reaction
2) Remains unchanged chemically
On the right/forward it is exothermic/endothermic
exothermic
On the left/backward direction it is exothermic/endothermic
Endothermic
As temperature increase which direction does it shift to
endothermic to try to cool the system
As temperature decrease which direction does it shift to
Exothermic to heat up the system
The haber process
The method of making ammonia
Ammonia equation
N2(g) + 3H2(g) <–> 2NH3(g)
Reaction conditiosn for the haber process
1) 450c, 200 atm, and iron catalyst
Why does the conditions for ammonia not use a lower temperature?
Low temperatures reduce the rate of reaction, so scientist compromise between yeild and rates
ammonium salts reacts with an alkali to produce: ammonia, water and a salt T or F
T
a really high temperature is used to speed up the reaction for the haber process
True
Pressure can be changed in 2 ways
Make the space smaller
Add more particles
Rates of reaction equation include unit
change in mass over time g/s
Change in volume over time
cm3/s
Hydration of salts
Some chemical equation can be reversed by adding water or by heating to remove water by evporation
What is the formula for vanadium(V) oxide
V2O5
CaCO3 reacts with HCL to form CO2 state 3 ways to decrease the rate of reaction
1) Increase particle size
2) Decrease concentration
3) Decrease temperature
Explain the term equlibrium mixture
In a reversible reaction, the rate of the forward reaction is equal to the reverse
^H meaning
Triangle and a H is change in enthalpy/ change in energy
Explain conditions of the haber process
1) 450c is used to increase rates of reaction, it causes the equilibrium to shift left so it is a compromise.
2) 200 atm is used to increase rates of reaction as distance between molecules decrease, it increases yeild of ammonia
3) Iron catalyst is used to increase rates of reaction by lowering activation energy
