It is important that only the temperature is changed since this is what is being investigated.
Method
Apparatus
I have chosen to use a 10cm3 measuring cylinder to measure the volumes of substances used since it is more accurate than a pipette. I will use an electronic water bath for maintaining the mixture at a temperature since the temperature is more accurate than a water bath above a Bunsen burner.
A 100cm3 gas syringe should be appropriately accurate for measuring the gas produced since it is accurate to 1cm3 of gas. I will use a three-figure balance to measure the mass of magnesium to be used since it is vital that as close to 0.1g of magnesium is used as possible.
Variables
After deciding how to approach all of the variables in the experiment I decided how to carry out my experiment. I decided to use different concentrations of HCl in 0.5M, 1.0M, 1.5M, and 2.0M (1mole/dm ). To obtain these different concentrations I used a solution of 1.0M which was already prepared and the same with a 2.0M solution. However in order to create a 0.5M and 1.5M solution I had to mix different solutions. The 0.5M solution was made using 10cm of deionised water and 10cm of 1.0M solution; this was then stirred with a glass rod. To make 1.5M solution the same concept was used; I mixed 10cm of 2.0M solution with 10cm of 1.0M solution.
I then measured and recorded how much volume of gas (cm ) was given off each 10sec using a stopwatch. Finally the gas syringe is an excellent piece of apparatus as it is very accurate, however I will have to make sure that the clamp does not hold on to it too tightly as this could effect the results.
To help obtain the best possible results I will repeat each experiment twice and then find an average set of data.
I predict that the high morality concentration solution will have a much faster rate of reaction than the weaker solution. I have predicted this from my knowledge of a previous experiment and scientific knowledge. I think that this happened because the more HCl in the solution the greater the concentration and there will be more particles colliding and more energy and therefore a faster rate of reaction. The reason I think that the rate of reaction will increase is that the experiment is exothermic, this means that it will give itself more energy and therefore more collisions and faster collisions. Also in the 2.0M solution compared with the 0.5M solution there are much more HCl particles in the same volume so the are going to collide with each other more often
Therefore I predict that the rate of reaction will increase with the concentration of the HCl solutions.
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 increase. 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.
Introduction
What is a reaction? A reaction is when two particles (reactants) join to form a new product or products.
What is rate? Rate is a measure of how fast or how slow something is. Rate is a measurement of the change that happens in a single unit of time, any suitable measurement can be used such as seconds, minutes, hours or even days.
What is the rate of a chemical reaction? The rate of a chemical reaction is how fast the reactants react.
How to find the rate of a reaction? In general to find the rate of a reaction, you should measure either the amount of reactant used up per unit of time or the amount of product produced per unit of time.
The rate during the reaction does not stay constant, it changes throughout the reaction, its greatest at the start but gets slower as the reaction proceeds. I think this is mainly to do with the fact the longer the reaction has taken place the more of the reactants react leaving fewer reactants with less chance of reacting.
Successful collision. For the reactants to be able to react they have to successfully collide with each other. The chance of a successful collision can be increased or decreased by using many different factors.
Temperature – Temperature alters the rate of a reaction by supplying the reactant particles with more energy, the more energy the reactants have the faster they move around increasing they’re are chance of bumping into one another and having a successful collision. Also the more energy they get from the heat the more particles have enough energy to react, this is known as activation energy. Generally the greater the temperature the faster the rate of a reaction, the rate doubles every 10°c. Surface Area – The greater the surface area of the reactants the more particles are available for a successful collision.
A Catalyst – A catalyst is a substance that changes the rate of a chemical reaction but remains chemically unchanged itself.
Concentration – Concentration effects the rate of a reaction because the higher the concentration of particles the greater the chance of a successful collision. The general trend for the concentration is the rate doubles as the concentration doubles (they’re directly proportionate).
What is Activation energy? Activation energy is the amount of energy required for the reactants to successfully react. The reactants need a certain amount of energy, any extra energy increases they’re chance of a successful collision.
Experiment
To investigate the rate of reaction I have decided to use the concentration as a variable. I am going to use marble chip (Calcium Carbonate) and Hydrochloric acid. I will alter the concentration of the hydrochloric acid each time, and I will measure the amount of Carbon Dioxide product given off.
I have chosen to use these because during the reaction Carbon Dioxide is given off, this is a gas and highly insoluble in water. The method I have planned will accommodate this.
Though some carbon dioxide is soluble in water the amount is negligible,
At room temp (20°c) in 1l of water 1.69 ´ 10 will dissolve.
Equation
Prediction \ Hypothesis
I think that the higher the concentration of hydrochloric acid the faster the carbon dioxide will be given off. I think this because the higher the concentration of acid molecules the more particles available to react. Also the higher the concentration of acid particles the more chance of a particle having enough activation energy. The more particles available at any one time with enough activation energy means that in a given time more of the product is produced, or it takes a less amount of time to produce a certain amount of product, in this case Carbon Dioxide. The activation energy is the amount of energy needed to make the two particles react, without it the particles would not successfully react.
Apparatus
Conical flask
Delivery tube
Measuring Cylinder ´2
Beaker
Bowl of water
Weighing scales
Stopwatch
Hydrochloric Acid Solutions and Marble chips
Diagram
Method
After collecting the apparatus and arranging as followed, fill the bowl full of water and measure out 30ml of 0.5-mol acid and pour into conical flask.
Weigh out the marble chip/s, try, and decide on a suitable weight because each time you will need to use the same weight. Place the chip/s into the conical flask and insert the bung.
As the reaction takes place bubbles should start to come out of the delivery tube into the upturned measuring cylinder. From the first bubble measure how long it takes for 20 ml of gas to be given off.
Record the result and refill the upturned measuring cylinder with water, wash out the conical flask and weigh out the next lot of marble chips.
Repeat the experiment but each time using a different concentration of acid 0.5 moles more each time until you get to 2 moles, you may want to repeat the experiment about three times to get a more accurate average for each concentration.
Safety
You will be using concentrated acid, so at all times you must be very careful, and you MUST wear goggles. If any spills onto your hands it should be washed off immediately and reported to the teacher.
Fair Test – Controlling the Variables
What I will keep the same –
Each time I repeat the experiment I will keep the temperature, surface area of the marble chips, amount of acid used, and the amount of carbon dioxide to be collected the same. These are the other factors, which may affect the rate of reaction.
What I will change – The only thing that I will change each time is the morality of the acid. Each time I will increase the morality by 0.5 moles, there is little problems with using the conical flask over because I am starting from the weaker to the stronger concentration of acid in turn.
Results Table
Graph of my Results
Conclusion
My results prove my hypothesis. The higher the concentration of acid the faster the rate of the reaction. The results also show that the research that I did also showed a valid pattern, as the concentration doubled so does the rate of reaction. Between 0.5 and 1.0 moles the amount of time roughly halves as the concentration is doubled, this is also true for the 1.0 and 2.0 mol gap. If my results had been more accurate I think the results would show the concentration of the acid and the rate of reaction to be proportional.
The graph also supports my prediction. On the graph the steeper the curve, the faster the rate of reaction. In addition, from the graph I was able to work out the average rate of reaction for the gas produced.
Evaluation
Overall I am pleased with my results and the way the experiment was carried out. I think my results were fairly accurate and proved my hypothesis. To make the overall experiment results more accurate we repeated it three times and then took the average. If I was to do this experiment again I would probably make it more accurate by using a Burette to measure the amount of gas given off, this would measure a lot more accurately the amount of gas given off. In addition, using smaller particles of marble chip so I could match up surface area and weight more accurately each time. I would like to then see if the concentration of acid is proportional to the rate of the reaction.
I had only one anomalous result due to the simplicity of the experiment; this is why I chose this factor to show the effect on the rate of reaction. The only odd result that I had was the third time I repeated the experiment on the 1.5 mol solution, the reaction took place a lot faster then the previous two. I think this was due to the marble chips that we were using. At first there was a large selection of marble chips available, so finding three to match the weight that I had set was pretty easy, by the time I had to repeat the experiment for the third time it was a lot harder, so in that instance instead of three chips being used I had to use five to make up the weight, this altered the surface area giving a larger area for it to react, which is why I think the reaction went a lot faster then expected. This is also why I’m interested into investigating further the effect of surface area on the rate of reaction.
In addition, other things that I would like to investigate would be the experiment of time against amount of gas produced to show at which points the rate of reaction was at best and the curve/line of reaction. I would like to also investigate other factors, which affect the rate of a reaction like temperature and surface area to see how they affect the rate of a reaction.
Some other areas in the experiment that I feel I could have improved on were factors like, controlling the stopwatch. There is lots of room for human error here. However, the inaccuracies due to them were negligible because I paid close attention to these during the experiment.