Chemestry Lab Rates of Reaction (Picture from: http://sciencespot. net/Pages/kdzchem. html) The rate of reaction is how fast or slow a reaction is completed. This is important for factories and chemists all over the world. What happenes during a reaction is atoms or molecules that collide and form new molecules. You can affect this rate of reaction with: temperature of reactants or suroundings, surface area of reactants, if there is a catalyst present, but in theis lab the concentration was changed as the IV. The reaction rate is masured in change/time, in this case it was: volume of gass produced/minutes.
Gas was measured in ml/minute, and this was the DV. Aim of lab was: To find the change in rate if reaction, depending on the concentration of hydrocloric acid. Hypothesis: If the concentration of hydrocloric acid is increased, the rate of reaction will increase and the volume of gass will increase. The reasoning behind the hypothesis is that when there are more molecules in the solution the reactants collide more often, so more product is made in a shorter periode of time. The equation was: Mg + 2HCl > MgCl2 + H2
Similar article: Measuring Reaction Rate Using Volume of Gas Produced
Independent variable| Dependent variable| Controled variables| Value| How to control the CV| Concentration of acid| Rate of reaction| Vol of acid| 20 ml| Measure using a 50ml Measuring cylinder| 2 moles pr. L| Vol of gas| Temp of acid| Room temp. | Not controlled, only montored| 1 moles pr. L| | Amount of Mg| 5 cm or ribbon/ 0. 07g| Ruler, and weight| 0. 5 moles pr. L| | Precence of catalyst| No| Not have a catalyst| 0. 25 moles pr. L| | Type of acid| Hydrocloric| Have same type of acid| Method: 1. Gather aparatus and materials, and set up as shown in diagram below aparatus list. 2. Bucket + water 3. Measure temp, in room and water 4.
Fill measuring cylinder with water 5. Rubber tube + sidearmed test tube 6. Obtain 0. 08 g using a weight, place in side-armed test tube 7. 20 ml HCl of 2 moles pr. L in measuring cylinder 8. Place measuring cylinder in bucket with water, upside down, without air leaking in to the cylinder when flipped. 9. Puor HCl into side-armed testtube. 10. Start the stopwatch 11. Close the top of the side-armed test tube by placing rubber tap 12. Weight 3 min. be accurate using the stopwatch 13. Record ml of gas produced 14. Reapeat the experiment twise pr. Concentration: 2 moles pr L, 1 mole pr. L, 0. 5 moles pr. L and 0. 25 moles pr. L Aparatus list: Sidearemd testtube – Rubber plug – Rubber tube – Bucket – Water – 2x 100ml measuring cylinder – 400ml Beaker – 40 ml in each concentration type of HCl acid, 2, 1, 0. 5 and 0. 25 M. Pr. L – 8x 0. 08g of Mg ribbon – Stopwatch Raw data table showing amount of gas created in the two trials of the experiment: Concentration in moles pr. L| Trial 1 – ml og gass produced in 3 min| Trial 2 – ml og gass produced in 3 min| 0. 25| 8| 10| 0. 50| 30| 32| 1. 00| 70| 73| 2. 00| 61| 65| First proceced data table showing average of gas made: Concentration in moles pr. L| Average of trial 1 and 2 in ml of gas produced in 3 min| 0. 25| 9| 0. 50| 31| 1. 0| 71. 5| 2. 00| 63| Proceced data table showing rate of reaction: Formula used=ml of gass produced/time (in seconds) Concentration in moles pr. L| Rate of reaction calculation in ml/sec| Rate of reaction result in ml/sec| 0. 25| 9/180| 0. 05| 0. 50| 31/180| 0. 17| 1. 00| 71. 5/180| 0. 40| 2. 00| 63/180| 0. 35| Graph showing the rate of reaction: Conclusion: As the results clearly show, the rate of reaction increases rapidly and this strongly supports my hypothesis. The amount of succesfull collisions increased, because of increased number of atoms in the product, so when the concentration was increased it rate of reaction increases.
There are more collisions because of more atomes, and therefor more succesfull once. Evaluation: Random errors: * Therometer used to measure temperature * Inaccuracy of +/- 1 C * Balance weight used to measure Mg ribbon * Inaccuracy of +/- 0. 01 g * Measuring cylinders used to measure volume of acid and volume of gas * Inaccuracy of +/- 0. 5 ml * Ruler used to measure Mg ribbon * Inaccuracy of +/- 0. 1 cm Ways to prevent random errors and improve the method: – Compleet the experiment more times Systematic errors: – As you see in the graph, the fourth result was anomalus.
During the 3 minutes the magnesium ribbon was “used up” in a very short period of time. The rate was so fast in the 2 moles per liter that it was over in under a minutte, but in the other concentration types it tok longer time for the reaction to compleet. Therefor we have to look away from the highest concentrations, and focus on the three lowest. This was a big weakness in the lab. – When pouring the HCl acid into the side armed test tube, some of the reaction had been compleeted before we had time to put the rubber stopper on every time. The temperature was only monitored, not controlled. Ways to reduce systematic errors and improve the lab: * Have a shorter reaction time: shorten the time form 3 min to around 1 minutte. * Use a fisle-funnle to prevent gas leaking out before the stopper is placed on the testtube. * Do the experiment in a controlled environment, like in a water bath. Sugestions to possible further investigations into this topic: You can change the IV, to one of the other factors that affect rate of reaction. Eg. Take the same concentration of HCl acid and change the temperature, or the precence of catalyst.