rate of reaction of limestone with citric acid - coffee machine de-scaler,

1. Friday, 12 July 2013

2.  Chemical reactions take place at very
different rates – some are very fast (like
explosions) and others may take months or
years to proceed.
 In a chemical reaction which produces a gas
the rate can be measured by determining the
volume of gas produced as time passes.
 Limestone produces carbon dioxide gas when
it reacts with an acid. The rate of production
of carbon dioxide can be measured in several
ways.

3.  In this experiment the reagents are calcium
carbonate (limestone) and citric acid.
 The products are calcium citrate, carbon
dioxide gas and water.
 The rate of the reaction is measured by
measuring how fast the carbon dioxide gas is
produced.
 The limiting reagent is the amount of citric
acid. This is the first reagent to be use up.

4. Measure
volume on a
measuring
cylinder

5. Rate of reaction experiment
Time (s) Volume of Carbon Dioxide (ml)
0 0
30 16
60 25
90 31
120 34
150 35
180 36
210 36
240 36

6.  We can record the rate using this relation|:
 Rate of reaction = change in recorded property
time for the change
 Actual rate is the gradient of the line of the
product concentration versus time graph.
 Average rate is the gradient of the line joining
the two point in time over which the rate is
being measured.

7. 0
5
10
15
20
25
30
35
40
0 50 100 150 200 250 300
Volumeofhyrdoger
Time (s)
Rate of reaction experiment.
Rapid
reaction here
Reaction slows
down here.
Reaction
stops here

8. 0
5
10
15
20
25
30
35
40
0 50 100 150 200 250 300
Volumeofcarbondioxide
Time (s)
Rate of reaction experiment.
Rate of reaction experiment Volume
of Hydrogen (ml)
Rate at the start of
the reaction.

9. 0
5
10
15
20
25
30
35
40
0 50 100 150 200 250 300
Volumeofcarbondioxide
Time (s)
Rate of reaction experiment.
Rate of reaction experiment Volume
of Hydrogen (ml)
Average rate of
reaction between
0s and 200s.

10.  Calculate the number of moles of carbon
dioxide produce in experiment 1 above.
 Volume of carbon dioxide = 36ml
 1 mole of carbon dioxide = 24000 ml
 Number of moles of carbon dioxide
 = 36 ÷ 24000
 = 0.0015 moles

11.  In this experiment calcium carbonate reacts
with ethanioc acid (acetic acid).
 The rate of reaction is measured by collecting
the carbon dioxide gas produced in a gas
syringe.
 The results can be processed in the same way
as those for experiment 1.

13.  In this experiment calcium carbonate reacts
with citric acid.
 The rate of reaction is measured the mass of
the remaining chemicals.
 The loss in mass is due to the escaping
carbon dioxide gas.
 The results can be processed in the same way
as those for experiment 1 except that the
factor changing is the mass and not the
volume.

15.  Concentration
 The higher the level of concentration (or
pressure in gases) the faster the reaction.
 This is due to increased collisions between
reacting particles.

16.  Surface area in solids
 The larger the surface area of a solid the
faster the reaction. Finely divided substances
have much larger surface areas than large
chunks of a solid.
 This is due to increased collisions between
reacting particles.

17.  Temperature
 The higher the temperature the faster the
reaction.
 This is due to increased and more energetic
collisions between reacting particles.
 A 10oC rise in temperature often results in a
doubling of the reaction rate.

20.  Only molecules with enough activation energy
will react to form the products.

21.  Catalysts
 Catalysts increase the rates of chemical
reactions.
 This is due a lowering of the activation
energy for the reaction.
 Catalysts are not consumed in the reaction so
in theory they can be used over and over
again. In practice they are often contaminated
and/or some is lost in a process.

24.  Scientists assume all gases are made of particles
in constant random motion. They have regular
elastic collisions with other molecules.
 Gas molecules collide with the walls of their
container and exert pressure but do not lose
energy in their collisions and do not attract other
molecules.
 The volume of actual gas molecules in a
container is negligible and their average kinetic
energy is proportional to the temperate (Kelvin).

25.  http://ie.dynapipe.co.uk/how-to-remove-limescale.htm
 http://en.wikipedia.org/wiki/Limescale
 http://www.movia.ro/decalcifiere_eng.html
 http://www.thor.com/view.asp?id=20130408120303AAmFq15
 http://www.newworldencyclopedia.org/entry/acetic_acid
 http://www.newworldencyclopedia.org/entry/Citric_acid
 http://en.wikipedia.org/wiki/Sulfamic_acid
 http://www.lihuasz.com/news/what_is_sulfamic_acif-en.html
 http://www.yangheng.com/zycp08.htm
 http://uk.answers.yahoo.com/question/index?qid=20130414114029AATzCWd
 http://www.howtocleanthings.com/appliances/how-to-clean-coffee-maker.htm
 http://chowhound.chow.com/topics/360882
 http://scottiestech.info/2009/04/22/descaling-appliances-which-acid-is-best/
 http://www.ceragol.com/en/products/premium-descaler/descaling/
 http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Acetic_acid.html
 http://en.wikipedia.org/wiki/Calcium_carbonate
 http://www.princeton.edu/~achaney/tmve/wiki100k/docs/Calcium_carbonate.html