How does the concentration of an acid effect the rate of reaction ?

I expect the graphs to roughly look as follows: _

A Controlled Experiment

   

      In this experiment we will keep it fair by only changing one variable. We will keep the concentration of acid, the length of the magnesium ribbon, the temperature and the volume of the solution (the acid and water) the same. It is very important to keep the temperature the same as if the temperature increases the particles will move faster and hence be involved in more collisions so the reaction will speed up. Or if the temperature decreases the reaction will slow down as the particles will be moving slower and thus be involved in fewer collisions. Although there is a very hard variable to control that is how well the solution is mixed when diluted, so we can get the correct concentration. A way to overcome this problem is to stir the solution at least a couple times. This is a very important variable to control as it determines the exact concentration of the solution and if not controlled probably could lead to inaccurate results. We will change the amount of acid and water used in the solution. We will always have 10ml in the solution but change the amount of acid and water used. For example we might use 4ml of acid, so we will use 6ml of water.

Method

      In this experiment we will first measure out the amount of water we are going to use and the amount of acid we are going to use. We then will put these in a beaker together. Then we will put the magnesium in with the solution and time how long it takes the magnesium ribbon to completely disappear, using the stopwatch. We will do this experiment twice so that we can get more accurate results using an average.

      We will do a preliminary experiment so that we can find out the range of numbers we are dealing with and it is also useful to do the experiment once before so that when we do it properly we know exactly what we are doing and can do it perfectly.

We will wear goggles for safety reasons.

We will set the apparatus up as follows: _

We will represent our results in a table like the following one: _

Results

 

Analysis

      From the curved graph it is evident that when the concentration is increased the average time taken is decreased. This is because of the collision theory, as I said in my explanation. As the concentration is higher there is a higher chance of an acid molecule colliding with a magnesium atom. So the reaction takes less time when the concentration is higher, as shown in the graph. Also the concentration is directly proportional to the rate of reaction. So, as I said in my prediction when the concentration doubles, the rate of reaction doubles.  

Evaluation

 

      In this experiment we have found out that average time taken decreases when the concentration is increased, which results in a curved graph, and that when the rate of reaction is directly proportional to the concentration, this graph shows a strong positive correlation.

      There aren’t any anomalies in the curved graph but in the other graph the first point is a small anomaly. This could be for a number of reasons. Half way through the experiment we started using a different reel of magnesium ribbon that could affect the results. The pieces of magnesium ribbon could have been slightly different so the time taken could have changed. Also the room temperature could have changed throughout the experiment so this could have affected the results. Furthermore the reaction time was ended when I thought it had finished but I might not have seen when the reaction had finished exactly. Also not all the liquid came out of the cylinder, which could affect the results in a major way. In addition when we measured out the amount of solution there could have been some impurities in the measuring cylinder. Also we could have improved the experiment by measuring the magnesium ribbon exactly, or making sure the room temperature is the same through the whole experiment.