Rates of Reaction: Magnesium Strips and Hydrochloric Acid Introduction Rates of reaction occur when two chemicals bond. The chemical bonds can be either very strong or very weak. I expect that when I add magnesium to the hydrochloric acid that depending on the amount of hydrochloric acid that the acid will eventually dissolve the magnesium and consequently produce hydrogen gas. All chemical reactions involve reactants. When these reactants are mixed together they cause a chemical reaction to occur which will make products. The reactants that I will use are hydrochloric acid and magnesium. I predict that the chemical reaction will take place as soon as the magnesium is dropped into the hydrochloric acid. Magnesium chloride and hydrogen gas are the products formed during this reaction. The formula equation for this experiment is: Magnesium + Hydrochloric acid = Magnesium Chloride + Hydrogen Mg + 2HCl = MgCl2 + H2 The reason that the magnesium reacts with...
Background information/scientific knowledge: To find out the rate of reaction of a substance you need to find out the time taken for the reactants to change into products. The particles of the product (magnesium and hydrochloric acid) need to collide often enough, hard enough, and with enough energy to break the bonds in order to react. When the reactants bonds break new bonds will form. The minimum amount of energy needed
3for this to take place is called activation energy (Ea).
There are 4 factors that effect the rate of reaction: temperature, concentration, using a catalyst and surface area.
Temperature
Increasing the temperature gives the particles more kinetic energy, the particles will then move faster and have more energy. So they will collide more often, and that will increases the likely hood of successful collisions. The higher the temperature the faster they move therefore increasing the temperature increases the rate of reaction.
Surface area
Collision can only take place on the outside. If a reactant is a solid cutting it up into smaller pieces will increase the surface area. This would mean that there is more area for the particles to work on so there will be an increased chance of successful collisions. Therefore increasing the surface area increases the rate of reaction.
Increasing the of a substance in solution
means that there will be more particles per dm3 of that substance.
The more particles that there are in the same volume
the closer to each other the particles will be.
This means that the particles more frequently with each other
and the rate of the reaction increases.
Using a catalyst
A catalyst also works on the surface area, it gives the reacting particles a surface to stick to where they will bump into each other, increasing the number of successful collisions. Therefore using a catalyst will increase the rate of reaction.
concentration
If a solution is more concentrated it means there are more particles of the reactant particles of the reactant knocking into each other in the same volume of solvent, this would increase the amount of successful collisions. Therefore increasing the concentration increases the rate of reaction.
How temperature affects rates of reaction There are a number of things that affect rates of reaction, such as temperature, concentration of acid, a catalyst, stirring, surface area, and pressure in experiments involving gasses. I have chosen to investigate temperature, which will be the only variable
* Rates of Reaction
Increasing the temperature increases the speed of the particles. The faster the particles move, the greater the number of collisions, and therefore the rate of the reaction increases. A 10OC rise in temperature almost doubles the rate of most reactions.
Chemical reactions take place by chance. Particles need to collide with enough velocity so that they react. As the temperature is increased the particles move faster since they have more energy. This means that they are colliding more often and more of the collisions have enough velocity to cause a reaction. Since there are more collisions the chemical reaction takes place faster.
Depending on certain factors the rate that this reaction will take place will either increase or decrease. The factors that may affect the rate of reaction are as follows:
· Temperature of the Hydrochloric Acid
· Mass of the magnesium ribbon used
· Concentration of the Hydrochloric acid
· Surface area of the magnesium ribbon used
All of these factors will change the rate of reaction because of the Collision Theory. This is a theory that is used to predict the rate of a reaction. The Collision Theory is based on the idea that for a chemical reaction to take place, it is necessary for the reacting particles to collide with each other with enough energy to break or form new bonds between the other particles, which is called a successful collision. If when they collide and they do not have enough energy to break or form new bonds then they will simple bounce of each other, causing an unsuccessful collision.
Factors
The factors that could affect the rate of reaction of my experiment are as follows:
· Concentration of acid
This could affect the rate of reaction because the higher the concentration of the acid then the more acid particles per 100cm3 so more collisions per second and then there will be more successful collisions per second.
· Temperature of the acid
If the starting temperature of the acid is different each time the speed at which the acid particles collide with the magnesium ribbon will increase more the higher the temperature goes. This means the acid particles move with more energy, which means they will collide with the magnesium with more energy, which will give more successful collisions per second.
· Surface area of the magnesium
If the magnesium had a bigger surface area each time the experiment was done, then the acid particles will have a bigger area to collide with, so more collisions will occur every second and the more collisions per second than the more successful collisions per second.
· Type of acid used
If you changed the type of acid then the rate of reaction would change. Hydrochloric, Sulphuric and Nitric acid all would produce a different rate of reaction, so if I do change the type of acid then all three kinds would produce a different set of results.
Variables:
The independent variables are fixed- volume of acid, length of magnesium
The dependent variable is what is being measure- the amount of gas
The controlled variable needs to be kept constant to ensure that it’s a fair test- length of magnesium, type of equipment, volume of hydrochloric acid, temperature
Fair Test:
To make my experiment a fair one, I had to look at a lot of things. Firstly, I looked at the factors that may have affected how well the investigation would work and these were things like using different equipment or doing the actual experiment in different conditions i.e. a colder/hotter environment. To combat this, I made sure that upon repeating the experiment, I used the exact same equipment and done it in the exact same environment to make absolutely sure that the experiment was fair at each temperature. I think that these were both very important factors because they could affect the results severely and leave me with an anomalous when I should only have correlating results. To ensure fair and accurate results, all of the factors that can affect my results need to be controlled.
* Variables
I have chosen to repeat the experiment 3 times because it therefore allows me to calculate an average rate of reaction. This will ensure that there are no abnormal results and it will increase accuracy. I have decided to start readings at 20OC and increase by 10OC each time until 60OC is reached, since it will allow me to see the increase in rate of reaction and 5 results should be enough to identify any trends.
Key factor
I have chosen to use the concentration of the acid as my factor that I will change. I chose this because several different concentrations can be made up before the experiment by the lab technicians and they will be able to make them accurately.
There will be several different concentrations of acid, which will give me a wide range of results, which will be reliable and reproducible.
Fair Test
In order to keep my experiment a fair test I will have to make sure that I keep the following factors the same:
· Starting temperature of the acid
· Volume of acid used (cubic centimetres)
· Surface area of the magnesium
· Clean the magnesium with emery paper before experiment
· Length of magnesium
I will also have to make sure that the gas syringe is correctly connected and that it is placed quickly and tightly enough so that no hydrogen gas escapes.
The following factor that I will change is:
· The concentration of the acid
Equipment/apparatus
The apparatus and chemicals used during my experiment are as follows:
Chemicals
Apparatus/equimptment
· Measuring cylinder
· Conical flask · Safety glasses
· Beakers
· Test tubes
- Tile
· Ruler
· Thermometer
· Scissors
· Glass rod
Eye protection
Hydrochloric acid (1mol/dm3)
Magnesium ribbon
Distilled water
Conical flask
Delivery tube
Water trough
Measuring Cylinders to collect gas, 30cm3
Stopwatch
Method
1. Put on safety goggles
2. Collect clamp stand, clamp and boss
3. Collect conical flask and measuring cylinder
4. Collect stop clock
5. Measure out 50 cm3 of 0.0M hydrochloric acid with the measuring cylinder
6. Pour hydrochloric acid into the conical flask
7. Collect thermometer
8. Measure the starting temperature of the hydrochloric acid
9. Measure 3cm of magnesium ribbon
10. Clean the surface of the magnesium with the sandpaper
11. Drop the magnesium into the conical flask
TEMP
6) Once the experiment is complete. Repeat all the experiments in the same way for accuracy.
7) From the results averages can be worked out and graphs can be plotted to show trends and patterns or to prove the prediction.
Experiment 1 Concentration of Acid(Moles) Initial Temperature(Degrees) Final
* Repeat experiment two more times (for accuracy) and record all results in a table.
* Repeat the experiment for temperatures of 30 OC, 40 OC, 50 OC and 60 OC
I am going to investigate how temperature affects the rate of reaction between magnesium and hydrochloric acid. The procedure for the experiment is as follows;
Method
1. Put on safety goggles
2. Collect clamp stand, clamp and boss
3. Collect conical flask and measuring cylinder
4. Collect stop clock
5. Measure out 15cm3 of 1.0M hydrochloric acid with the measuring cylinder
6. Pour hydrochloric acid into the conical flask
7. Collect thermometer
8. Measure the starting temperature of the hydrochloric acid
9. Measure 3cm of magnesium ribbon
11. Drop the magnesium into the conical flask
12. Quickly place the rubber bung into the conical flask
13. Start timing with the stop clock
12.Wait to see how long it takes for 30 ml of gas to form.
Safety
The things that I will need to do to keep my experiment a safe one for myself and other students around me are as follows:
· Wear safety goggles as I am using concentrated hydrochloric acid
· Care to eyes and the skin besides all the other people is always vital and necessary
· Care in using glassware since it is sharp when broken and can cut skin
· Safe disposal of reagents and laboratory chemicals
· Care when returning all used glassware and equipment at the end of the experiment
