# Rate Of Reaction Investigation by dffhrtcv3

VIEWS: 2 PAGES: 21

• pg 1
```									Rate Of Reaction Investigation

D. Crowley, 2008
Friday, June 22, 2012

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

   Add a small amount of magnesium ribbon to this, and place

   Finally take you thumb off the top, and quickly place a lit splint
over top of the test tube
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 pop when it ignites

Magnesium + Hydrochloric Acid → Magnesium Chloride + Hydrogen

Mg + 2HCl → MgCl2 + H2
Balloon
   Many metals react with acids – producing the gas hydrogen

   A burning splint is the test for this, producing a squeaky pop
when it ignites

   Watch the balloon hydrogen demo…
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 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
   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

   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
   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
   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
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
   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
   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
   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

Mass of   Time for test tube to fill with H2 (sec)
Mg (g)

1       1           2             3         Average

2
3

4

5 etc…
Results - Volume

Volume     Time for test tube to fill with H2 (sec)
HCl (cm3)

10       1           2             3         Average

20
30

40

50 etc…
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
Conclusion
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

Rate Of Reaction Between Mg + HCl

35
Time Taken For Test
Tube To Fill (sec)

30
25
20
15
10
5
0
0   1           2           3          4    5   6
Mass Mg (g)
Graph

Rate Of Reaction Between Mg + HCl

30
Time Taken For Test
Tube To Fill (sec)

25
20
15
10
5
0
0   10       20         30           40   50   60
Volume HCl (cm3)
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