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IB1 Chemistry Topic 6: Kinetics Rates of reaction. Why are some chemical reactions over in seconds while others take years?. Image : https://en.wikipedia.org/wiki/ Explosion , https://en.wikipedia.org/wiki/ Rust. Rate of reaction. - PowerPoint PPT Presentation
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IB1 ChemistryTopic 6: Kinetics Rates of reaction
Why are some chemical reactions over in seconds while others take years?
Image: https://en.wikipedia.org/wiki/Explosion, https://en.wikipedia.org/wiki/Rust
Rate of reaction
the increase in the concentration of a product ordecrease in the concentration of a
reactant with time
moldm-3s-1
Measuring rates
mass or volume changes as a gas is evolved
colour changes (using a spectrometer)
pH changes
conductivity changes for ionic solutions
Rate of reaction Mg and HCl using a gas syringe
Use a 4cm piece of Mg and 25cm3 1M HCl
Find the mass of the magnesium
Measure the volume of gas at 10second intervals
Calculate the concentration of the HCl
Draw a graph of concentration against time
Calculate average rate
Calculate instantaneous rate from gradient of graph
Collision theory
particles must collide
in the right orientation
with enough energy (minimum energy is activation energy)
Image: http://en.wikipedia.org/wiki/Traffic_collision
Reaction rates in solution
Image: http://www.chemguide.co.uk/physical/basicrates/concentration.html#top
Effect of surface area
Effect of surface area
Effect of temperature on reaction rate
HCl(aq) + Na2S2O3(aq) NaCl(aq) + SO2(g) + S(s) + H2O(l)
Maxwell-Boltzmann distribution
Image: http://chemwiki.ucdavis.edu/Physical_Chemistry/Kinetics/Rate_Laws/Gas_Phase_Kinetics/Maxwell-Boltzmann_Distributions
Activation Energy, Ea
Image: http://en.wikipedia.org/wiki/Activation_energy
the minimum energy required to start a chemical reaction.
Catalysts
A catalyst increases the rate of a chemical reaction, but is not used up during the reaction.
Catalysts reduce the activation energy.
Transition metals are often useful catalysts.
Enzymes are catalysts in biological systems.
What sank the Kursk?
The Kursk torpedoes contained hydrogen peroxide , and one theory suggests this might have caused the explosion.
Plan an investigation into the catalysis of H2O2
Image: http://en.wikipedia.org/wiki/File:Kursk_wreck.jpg
Links
http://phet.colorado.edu/en/simulation/reactions-and-rates
http://en.wikipedia.org/wiki/Russian_submarine_K-141_Kursk
http://www.youtube.com/watch?v=iTcogT-m2mk
http://www.rsc.org/education/teachers/resources/aflchem/resources/63/index.htm