Reaction between Magnesium and Hydrochloric Acid

Reaction between Magnesium and Hydrochloric Acid
I am going to investigate how the concentration of the acid in the reaction affects the speed at which the gas, hydrogen, is given off. Magnesium + Hydrochloric acid -?> Magnesium chloride + Hydrogen Mg + 2HCl -?> MgCl2 + H2 Prediction I predict that as I increase the concentration of the hydrochloric acid, the speed the gas is given off will also increase. I think this because the reaction is caused by collisions between the acid particles and the metal particles. As I increase the concentration of the acid, more acid particles will be in the same volume of solution. This means that the collisions are more frequent, therefore the rate of reaction is faster and the gas is given off quicker. Preliminary Experiment I am going to use different concentrations of acid in the experiment to find the highest and the lowest molar values of acid I will use in the actual experiment. I will test values between 0.2 and 2 molar acid. To obtain the correct concentrations, I will mix the acid with water. Concentrations of acid(using 50 ml of solution. Concentration HCl H2O 2M 50 5 1.8M 45 10 1.6M 40 15 1.4M 35 20 1.2M 30 25 1.0M 25 30 0.8M 20 35 0.6M 15 40 0.4M 10 45 0.2M 5 50 I am not going to carry out the experiment with 0 molar acid, as this would be reacting the magnesium with water, and magnesium does not react with water, only steam. I will carry out the experiments at room temperature, using 50ml of solution and 0.25g magnesium ribbon in four equal pieces. I will time how long it takes to displace 100cm3 water with hydrogen gas. I have chosen to displace 100cm3 because I worked out that the largest volume of gas the experiment will give off is 250cm3. I did a molar calculation to work this out: Mg + 2HCl -?> MgCl2 + H2 0.25g magnesium= ?volume of hydrogen. Mass=0.25 Ar=24 Mass/Ar=Moles: 0.25/24=0.010416666 Moles x 24000cm3=volume of hydrogen: 0.010416666 × 24000cm3= 250cm3 Results Moles of acid Time taken to displace 100cm3 water (secs) 2M 6 1.6M 7 0.2M Too slow-dnf 0.6M 84 For my final experiment I will test molar values between 0.6M and 1.6M. I found that 2M acid displaced the water too quickly for me to record the results accurately, and 0.2M displaced the water extremely slowly and I did not have time to complete the experiment. I could have made my preliminary experiment more accurate by taking the results three times to obtain an average. Unfortunately my time was limited and I did not have time to do this. Final Experiment Apparatus ? Conical flask. ? Delivery tubing. ? Magnesium ? Hydrochloric acid. ? 100cm3 measuring cylinders. ? Water basin. ? Water. ? Timer. Method I will measure 0.25g magnesium and dilute the hydrochloric acid to the required strength. I will set up the apparatus as shown above, filling the measuring cylinder with water to be displaced. I will then put the magnesium into the hydrochloric acid, put the bung in the flask and time how long the water takes to displace. To obtain accurate results I will repeat each experiment 3 times and work out an average. To make the experiments fair I will keep the following things the same and just change the acid concentration: ? Amount of magnesium. ? Temperature of experiment. ? Amount of solution. ? Surface area of magnesium. I will wear safety glasses to make the experiment safer. Results Concentration of HCl (M) Time taken to displace 100cm3 water (secs) 1 2 3 Average time taken 0.6 88 98 131 106 0.8 44 45 44 44 1 24 27 26 26 1.2 14 16 13 14 1.4 10 11 11 11 1.6 8 3 8 6 Conclusion I discovered that my prediction was correct, as the concentration of the acid increased, so did the amount of hydrogen given off. This was because as I increased the concentration of the acid, there were more acid particles in the same volume of solution, and so there were more collisions between the acid and the metal particles, making the rate of reaction faster and so the hydrogen was given off quicker. The graph shows that the results all followed a very similar trend, as my curve of best fit is smooth. As I did the experiment and drew my graph, I noticed that the gap between the results for the lower molar values were much further apart than the results for the higher values. Evaluation The experiment went very well, I obtained the results I expected and the results were accurate. I found only one anomalous result and this was only slightly out of the trend of the other results. This anomalous result could have been caused by a delay to put the bung in the conical flask, so losing some of the gas. Their could also have been slight parallax errors in reading the results off the measuring cylinder. To make my work accurate I did the following: ? Made sure I had the same amount of magnesium each time. ? Measured all the liquids from the meniscus in the measuring cylinders. ? Started the timer at the same point each time: when the bung was replaced to the flask. ? Cleaned the measuring equipment before each experiment. There were factors that could have made my work inaccurate, such as the fact that I had to carry out the experiment on different days and I only had an hour on each of the days. Some other things that may have made my results inaccurate are: ? The temperature in the laboratories may not have been the same on the different days. ? The timers may not have been accurate. ? There may have been errors in my recording of the results when the displacement had finished. I could have made my experiment better by carrying out all the experiments on the same day and in a controlled environment. I could have used a gas syringe to collect the gas, instead of a measuring cylinder, This would have made it more accurate. I could also have taken more readings to prove the trend better and to make the results and graph more accurate.

Reaction between Magnesium and Hydrochloric Acid 8.5 of 10 on the basis of 3421 Review.