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