Group+7

=How will concentration affect the rate of reaction between hydrochloric acid and magnesium?=

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Aim:
To find out how the different concentration of the hydrochloric acid affects the mass of the product in a certain amount of time. magnesium(s) + hydrochloric acid(aq) ---> magnesium chloride(aq) + hydrogen(g) Mg(s) + 2HCl(aq) => MgCl2(aq) + H2(g)

Hypothesis
The less concentrated the hydrochloric acid, the more time it will take for the reaction to go into completion. As stated in the collision theory,the speed of chemical reactions can be altered by increasing or decreasing the concentration of the reactant, as there will be less collisions between the particles with the dilution of the reactants.

Variables

 * Independent variable: the different concentration of hydrochloric acid (1.0M, 0.8M, 0.6M, 0.4M)
 * Dependent variable: change in mass of hydrogen gas with time
 * Controlled/constant variables: one cm strips of magnesium ribbon, room temperature

**Materials:**

 * Four 125ml Erlenmeyer flasks
 * four 1cm strips of magnesium ribbon
 * Stop watch
 * 28ml of hydrochloric acid
 * electronic balance
 * 12ml of distilled water
 * 2 measuring cylinders
 * 2 pipettes



Method:

 * 1) Set up the electronic balance
 * 2) Measure with a pipette:
 * 3) · 10ml of 1.0M hydrochloric acid with a measuring cylinder
 * 4) · 8ml of hydrochloric acid and 2ml of distilled water with a measuring cylinder
 * 5) · 6ml of hydrochloric acid and 4ml of distilled water with a measuring cylinder
 * 6) · 4ml hydrochloric acid and 6ml of distilled water with a measuring cylinder
 * 7) Label 4 Erlenmeyer flasks with the concentration of HCl (1.0M, 0.8M, 0.6M,0.4M)
 * 8) Pour all four solutions into the 4 different 125 ml Erlenmeyer flasks
 * 9) Cut four 1 cm long strips of magnesium ribbon
 * 10) Weigh the 1.0M HCl with the magnesium ribbon inside the electronic balance
 * 11) Repeat step 10 for the other 3 solutions
 * 12) Record the initial mass in a table
 * 13) Prepare stopwatch
 * 14) Start stopwatch whilst placing the magnesium ribbon inside the Erlenmeyer flask with 10ml of 1.0M hydrochloric acid
 * 15) Record the change in mass of the solution every 10 seconds
 * 16) Repeat steps 12 & 13 for the other three solutions
 * 17) Record results in a table

Data Collection:
Table 1: Concentration of Hydrochloric Acid vs. Change in Mass of Hydrogen Gas Through Time

While the magnesium was reacting with the hydrochloric acid, bubbles(hydrogen gas) appeared throughout the solution, and this reaction continued until the magnesium strip completely disappeared. The solution produced heat energy, as the solution was warm when the reaction was finished.

Conclusion:
The aim of the experiment was achieved. As stated in the hypothesis, ‘The less concentrated the hydrochloric acid, the more time it will take for the reaction to go into completion.’ This was proved true during the course of the experiment. The dilution of the hydrochloric acid with distilled water decreased the speed of chemical reaction. As there were less particle collisions, the time taken for the magnesium ribbon to react with the hydrochloric acid takes much longer, as shown in the table. The time and change in mass of hydrogen gas have a positive relationship. When the time increases the change in mass of hydrogen increases as well. Concentration is one of the four factors that affect the speed of a chemical reaction. The steeper the slope, the faster the rate of the reaction; in other words, the faster the rate that Hydrogen gas is produced. The more acid particles there are, the more collisions will occur between the particles, therefore the speed in which the chemical reaction requires to go into completion will increase. The results for the first 3 solutions were expected, but the solution with 0.4M didn't fit with the hypothesis. No explanation can be made to explain the irregular behavior.


 * The measuring of the change in mass requires the opening of the top of the electronic balance for accurate results. At the beginning, the top was left closed, so the experiment had to be repeated.
 * Three centimeter magnesium ribbons were used, but the process of the reaction took too long, so the length of the ribbons were adjusted to just one centimeter.
 * The incorrect use of the measuring cylinder resulted to the re-measuring of the distilled water and hydrochloric acid. The meniscus of the liquids were not at eye-level to the designated amount.
 * How will other different substances react with hydrochloric acid? A further investigation can be explored on the relationship between chlorine, iron and sodium with hydrochloric acid.