Rates of Reaction
What is a rate of reaction?
The amount of change of a product or reactant in a given time.
What affects the rate?
a) Concentration of solution (more likely to collide as more in same vol.) b) Temperature (increases speed of molecules, more exceed EA)
c) Surface area (same as concentration)
d) Pressure of gasses (same as conc.)
e) Catalyst (guide particles to correct orientation + lowers EA)
f) Others e.g. light(light = increase in speed of particles)
How are rates altered?
Collision theory:
Particles must collide with an energy exceeding the EA and they must have the correct orientation.
A reaction rate increased by,
- Increasing collision frequency
- Increasing average kinetic energy of particles
- Lowering activation energy
- Giving molecules correct orientation
Effect of concentration on rate
rA = rate of reaction with respect to A
E.g. RH+ = rate of reaction with respect to H+(aq)
Rate of reaction = K [A]a [B]b [C]c
Units of rates of reaction = mol dm-3 s-1
Units of concentration = mol dm-3
Indices a, b, c etc: order of reaction - what is the effect on the rate of doubling the concentration
E.g. [H+]1 = 1st order = if conc. is doubled, rate is doubled
[H+]2 = 2nd order = if con. is double, rate is quadrupled
[H+]0 = zero order = if conc. is doubled, rate is unaffected
The constant, K
K = rate constant. This is a constant of proportionality
Units may vary but must include s-1
rA = k[A]1[B]1
mol dm-3 s-1‑ = k (mol dm-3)(mol dm-3)
for mol dm-3 s-1 to = mol dm-3 s-1
because k must = dm3 mol-1 s-1
because (mol dm-3)(mol dm-3) = mol2 dm-6, so to equal this out,
k = dm3 mol-1 s-1
Expt. 11.2a the kinetics of the reaction between calcium carbonate and hydrochloric acid
CaCO3(s) + 2HCl(aq) ® CaCl2(aq) + CO2(g) + H2O(l)
Collect gas given off in a syringe.
Create a table:
Time (s)
Volume of CO2 Vt (cm3)
(Vfinal - Vt) cm3
Then to find the order, find the half - life if time periods are roughly the same between each half - life then it is first order. If it is second order the graph would increase and not be constant.
Methods of following a reaction
By titration
E.g. reaction between iodine and propane in acid solution.
Then on a graph time can be plotted against titre values, in this case a straight line is seen, suggesting the reaction to be zero order
By colorimetry
Can be used when one of the reactants or products have a colour, the intensity changing during the reaction. The intensity can be followed using a special colorimeter.
By Dilatometry
Where during the reaction the total volume of the solution changes.
This process allows us to determine the reaction order. When changing the concentration of the one particular reactant we are able to calculate the order based on the change in reaction rate.
It is important however to note that the NH4 and K ions are still in
Investigating Rates of Reactions My aim is to investigate what factors affect the rate of reaction between magnesium and hydrochloric acid. The factor that I will be focusing on is the concentration of Hydrochloric acid. [IMAGE]Reaction Equation: Mg (s) +2HCl (aq) = MgCl2 (aq) +H2 (g)
...e will also become faster. In phase one, Nature of the Reactants five different metals were placed in the 2M HCl they all reacted differently with magnesium being the most reactive and copper being the least reactive. In phase two, Concentration, zinc was placed in different concentrations of 6M HCl. The higher the concentration was the more reactive the metal was. Next in phase three, Temperature, zinc was added to 6M HCl which was a different temperatures and the zinc was the most reactive with the HCl in the boiling water and least reactive with the HCl in the ice bath. Then in phase four, Surface Area, the powered zinc was more reactive then the piece of zinc in the 6M HCl because it had more surface area to be covered than the piece of zinc. Lastly in phase 5, Catalyst, the 3% H_2 O_2 was reactive with the 5 drops of 〖FeCl〗_3 but not with the 5 drops of water.
because I think it will give a wide set of results to put into a
The Effect of Concentration on Reaction Rate Introduction I will be carrying out an investigation into how concentration affects reaction rate. I will be looking at sodium thiosulphate and hydrochloric acid. The reaction is represented by the following equation: [IMAGE]Na2S2O3(aq) + 2HCl(aq) 2NaCl(aq) + H2O(l) + SO2 (g) + S (s) I will add the hydrochloric acid to the Sodium Thiosulphate and time how log it takes for the mixture to turn opaque. I will use a different concentration of Sodium Thiosulphate each time. Prediction
In order to find a good set of results for this experiment I need to
being used up, for that is a property of a catalyst is, it speeds up a
Investigation looking At the Speed of Reactions Introduction The aim of this experiment is to find out how a variable can affect the results from a scenario set up in scientific environment. The experiment is to see how a certain variable will affect the amount of Gas produced from a Calcium Carbonate and Hydrochloric Acid Reaction. The Science Calcium Carbonate is a generally white or colourless mineral that is translucent.
Investigating Factors that Affect the Rate of Reaction There are certain factors which affect the rates of reaction in an experiment. These factors are: · Pressure · Temperature · Concentration * Surface area / particle size and * The addition of a catalyst The factors that I will be concentrating on are temperature, concentration and surface area / particle size. Pressure Pressure influences the rate of reaction only when the reactants are in their gas phase. Pressure does not affect them much when they are either solids or liquids.
Rates of Reaction Reactions Reactions can only occur when two different particles come together. The theory for the way the reaction occurs is called The Collision Theory. The collision theory states that that the different particles need to collide with each other in order to react. However, they do not react if they collide without sufficient energy, and therefore the more energy a particle has, the more likely it is to react.
The effect of concentration on the rate of reaction between sodium thiosulphate and dilute hydrochloric acid
In order to make it a fair test the volume of hydrochloric acid had to
Rate of Reaction Investigation Aim: To determine how changing the concentration of a reactant (Na S O ) affects the rate of the reaction. Prediction: I predict that when we increase the concentration, the rate will increase; therefore there are more particles and a greater probability of a collision. If more particles are present in the same volume, they will be closer together. This means they have a higher probability of colliding and speeding up the reaction. If we double the concentration, the rate will also double.
The rate of reaction is how quickly or slowly reactants in chemical reactants turn into products. A low reaction rate is when the reaction takes a long time to take place; hence, a reaction that occurs quickly has a high reaction rate. A rate refers to how slow or quick the product is produced. It is possible to control the rate of chemical reactions and speed up or slow down the rate of chemical reactions by altering three main factors which are temperature, concentration and the surface area. When the temperature of the reactants increases, the molecules vibrate at a more intense speed therefore colliding with each other more frequently and with increased energy resulting in a greater rate of reaction. Accordingly, as the temperature decreases the molecules will move slower, colliding less frequently and with decreased energy resulting in the rate of reaction decreasing. Concentration is how much solute is dissolved into a solution and is also a factor that affects the rate of reaction. When the concentration is greater this means there is an increased amount of reactant atoms and molecules resulting in a higher chance that collisions between molecules will occur. A higher collision rate means a higher reaction rate. Consequently at lower concentrations there are reduced chances of the molecules colliding resulting in a lower reaction rate. The measurement of how much an area of a solid is exposed is called the surface area. The quicker a reaction will occur the more finely divided the solid is. For example, a powdered solid will usually have a greater rate of reaction in comparison to a solid lump that contains the same mass for it has a lower surface area than the powdered solid.