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Rate Of Reaction Investigation. D. Crowley, 2008. Rate Of Reaction Investigation. Your task is to investigate what affects the rate of reaction between magnesium ribbon and hydrochloric acid

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Rate of reaction investigation

Rate Of Reaction Investigation

D. Crowley, 2008


Rate of reaction investigation1

Rate Of Reaction Investigation

  • Your task is to investigate what affects the rate of reaction between magnesium ribbon and hydrochloric acid

  • As you complete this experiment you need to think how you can make this test a fair one, how you can be accurate and precise, and how you can ensure the results are reliable


Initial experiment

Initial Experiment

  • Set up an experiment with 5ml hydrochloric acid in a test tube

  • Add a small amount of magnesium ribbon to this, and place your thumb over the top

  • Finally take you thumb off the top, and quickly place a lit splint over top of the test tube


Initial experiment1

Initial Experiment

  • What caused the squeaky pop?

  • Can you write a word / symbol equation for the reaction?

  • Many metals react with acids – producing the gas hydrogen

  • A burning splint is the test for this, producing a squeaky popwhen it ignites

Magnesium + Hydrochloric Acid→ MagnesiumChloride + Hydrogen

Mg + 2HCl→MgCl2 + H2


Balloon

Balloon

  • Many metals react with acids – producing the gas hydrogen

  • A burning splint is the test for this, producing a squeaky popwhen it ignites

  • Watch the balloon hydrogen demo…


Initial questions

Initial Questions

  • Different reactions can happen at different rates: -

    • Reactions that happen slowly have a low rate of reaction

    • Reactions that happen quickly have a high rate of reaction

  • Initially you need to brainstorm what could affect the rate of reaction between the magnesium and the hydrochloric acid: -

    • What does the reaction need to take place (what are the reactants)

    • How could you compare the rate of reaction if you changed some of the independent variables


Initial questions1

Initial Questions

  • The rate of a reaction can be measured by measuring the rate that a reactant is used up, or by measuring the rate that a product is formed

  • Temperature, concentration, pressure of reacting gases, surface area of reacting solids and the use of catalysts are all factors which affect the rate of a reaction

  • *A catalyst changes the rate of a reaction, without being used up itself


Key words

Key Words

  • During your investigation you will come across some key words: -

    • Accurate: a measurement that is close to the true value (accuracy can be increased by controlling the key variables)

    • Precision: this is a more precise measurement, which can be achieved by using a smaller scale

    • Reliability: the experiment needs to be repeatable – if someone else did the experiment then they should get exactly the same results: this comes from repeating your experiment

    • Dependent variable – what is changed by the experiment (what you are going to measure)

    • Independent variable – what you change

    • Control variable(s) – what you are going to keep the same, making the experiment more accurate


Introduction

Introduction

  • Initially write you introduction for the rate of reaction investigation

  • Note your aim (what we are doing); why we are doing it and what tests which will carry out and why

  • I.e.

    • What does the reaction need to take place (what are the reactants)?

    • How could you compare the rate of reaction if you changed some of the independent variables?

    • What is it you are going to measure?


Method

Method

  • Your task is to now consider what methods you are going to use to measure the rate of reaction between the Mg + HCl

  • How are you going to make your experiment: -

    • Accurate (as close to the true value as possible)

    • Reliable (so someone else can repeat this experiment and get similar results)

    • Precise (how many readings are going to be taken and how can you ensure each repeat is completed in the same way)

  • Complete a step-by-step guide to completing your experiment

  • Note your independent variable (thing you change) and how you will change this

  • Note your dependent variable(s), and how you will measure this

  • What data are you collecting / recording


Method1

Method

  • You need to complete two experiments: initially changing the mass of magnesium (experiment 1) and then changing the amount of hydrochloric acid (experiment 2)

  • Submerge a test tube in a tub of water, ensuring the test tube is filled completely

  • Measure the mass of magnesium (keeping all other factors the same) and add this to a conical flask with the delivery tube going into the test tube

  • Record how long it takes for the test tube to fill up with hydrogen gas, and then repeat…

  • For the second experiment keep everything the same (including a known mass of magnesium) but this time add different volumes of hydrochloric acid to the conical flask


Prediction

Prediction

  • What do you expect will happen when you change the independent variable

  • Can you explain what will happen, and why you think this

  • E.g. I think that when I change the… the… will… because…

  • We should find a difference in the rate of reaction based on the mass of magnesium / volume of hydrochloric acid – both an increased mass and volume should increase the rate of reaction, if these are currently limiting factors


Apparatus order form

Apparatus Order Form

  • Finally, you will need to order all the apparatus your require to carry out this experiment

  • Ensure you have thought of everything, and just as importantly you must identify how much equipment you need – e.g. 5g magnesium ribbon; 1x conical flask; 50cm3 1M hydrochloric acid etc…

  • Your apparatus form must be signed off before it will be given to the laboratory technicians


Results

Results

  • Produce a results table for the two experiments (how mass of magnesium and volume of hydrochloric acid affects the rate of reaction)

  • Remember to include your units and how many repetitions you will be doing


Results mass

Results - Mass


Results volume

Results - Volume


Experiment

Experiment

  • You have this lesson to complete your experiments

  • Remember to be as accurate and precise as possible, repeating an appropriate amount of times and recording your results

  • You will also need to calculate all the averages this lesson for your results


Conclusion

Conclusion

  • Your task is to graph your results – one graph for the mass and one for the volume changes

  • A scatter graph is most suitable – mass of Mg / volume of HCl on the x axis, and time taken for the test tube to fill (seconds) on the y axis

  • Remember to add a title; units etc…

  • Once you have drawn your graphs you need to complete an analysis – what do the results show you / why do you think this is?


Graph

Graph


Graph1

Graph


Evaluation

Evaluation

  • Finally you need to complete an evaluation – were there any anomalous results?

  • What errors may have caused these: -

    • Random error (happens occasionally)

    • Systematic error (same mistake occurred every time (likely due to you measuring this incorrectly)

  • How accurate was your experiment – did you consistently get the same results?

  • Was your method fair allowing you to collect accurate results?

  • Do you have enough reliable evidence to support the conclusion that you have made

  • What improvements would you do if you could repeat this experiment?


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