IB | Higher Level Chemistry IAHow does concentration of hydrochloric acid affect its rate of reaction with magnesium?IntroductionThis investigation will explore how the rate of reaction of magnesium and hydrochloric acid varies with the concentration of hydrochloric acid. Magnesium is relatively high on the reactivity series, so it will react with dilute hydrochloric at room temperature quite quickly. According to kinetic-molecular theory, increasing concentration will increase rate of reaction, as increased concentration leads to a greater number of collisions between reactant particles every second, which is one of the conditions necessary for a reaction to take place. This leads to an increased number of successful, reacting collisions, increasing the rate of reaction.The acid-metal reaction can be expressed in a chemical equation:Mg (s) + 2HCl (aq) -> MgCl2 (aq) + H2 (g)The reaction should produce hydrogen gas, which will cause noticeable effervescence (a white gas) during the reaction. When the reaction is complete, no more gas will be produced, so the data collection in each trial will conclude when effervescence has stopped.The investigation will vary concentration of hydrochloric acid, which could be done by selecting different molarities of already-prepared acid. A convenient alternative is to manually dilute a known volume and concentration of hydrochloric acid to produce acid solutions of different molarities. The molarity of a solution can be calculated using the formula:

Where m1 and m2 are the final and initial concentrations and v1 and v2 are the total volume of solution and volume of solvent respectively. To calculate the amount of solvent necessary to create 0.2M of hydrochloric acid solution, the method below is used.

Calculation

VariablesIndependent: volume of 1M hydrochloric acidDependent: time taken for reaction to go to completionControl variables are discussed in Table 1:Controlled variableHow it will be controlledValue

Length of magnesium ribbonMeasure with a ruler and cut to appropriate length with scissors.5cm

Total volume of acid solutionMeasure out same volume of acid for all trials. Make up to required concentration with distilled water.50cm3

TemperaturePerform experiment indoors, away from sources of heat. Regulate temperature Measure room temperature at start and end of experiment.25C

Table 1: Controlled variablesMethodology1. Measure out 40cm3 of distilled water with a measuring cylinder2. Pour into a beaker3. Measure out 10cm3 of 1M hydrochloric acid with a measuring cylinder4. Pour into beaker of distilled water to make acid solution5. Cut 5cm length of magnesium ribbon6. Rub oxidized layer with sandpaper until ribbon is completely shiny7. Add magnesium ribbon to acid solution8. Start stopwatch9. Record qualitative observations in Table 210. When effervescing stops, stop the stopwatch and record time11. Repeat steps 1-10 twice12. Repeat steps 1-9 for the rest of volumes shown below in Table 2Safety: wear goggles and lab coat, remain standing, take care when handling acid, dilute acid by pouring acid into waterData tableVolume(cm3 2)Concentration of solution(mol dm-3 0.05)Time to completion(s 1)

Hydrochloric acidWaterTrial 1Trial 2Trial 3

10400.2

20300.4

30200.6

40100.8

5001.0

Table 2: Raw quantitative data table for experimentationConcentration of solution(mol dm-3 0.05)Qualitative observations

0.2

0.4

0.6

0.8

1.0

Table 3: Raw qualitative data table for experimentation