6. rate of reactions Flashcards
1
Q
measuring rate of reactions
A
- volume of gas produced
- change in mass of reaction (solid/aq reactants ⇨ gas
- time taken for colour/solid to appear/disappear
- change in temperature
- change in conductivity of solution
- change in pH
- change in pressure
2
Q
collision theory
A
- for chemical reactions to occur, particles must posses certain amount of energy (Ea)
- energy possesed > or = to Ea, reaction occurs when particles collide
- energy possesed < Ea, no reaction occurs, particles just bounce off each other
3
Q
factors affecting rate of reaction
A
- pressure of gas
- concentration of solution
- size of solid reactants
- temperature
- catalysts
- enzymes
4
Q
pressure of gas
A
- at higher pressure, more particles per unit volume
- increased FOC
- increased FOEC
- increased rate of reaction
5
Q
concentration of solution
A
- higher concentration, more particles per unit volume
- increased FOC
- increased FOEC
- increased rate of reaction
6
Q
size of solid reactant
A
- in powder form vs in clump form
- smaller sized, increased total exposed surface area to unit volume ratio
- more surface area for other reactants to collide
- other reactants can attack it more easily
- increased FOC
- increased FOEC
- increased rate of reaction
7
Q
temperature
A
- at higher temperatures, particles gain more kinetic energy
- proportion of particles with E > or = to Ea increases
- increased KE, move faster
- increased FOC, particles collide with each other with more energy
- increased FOEC
- increased rate of reaction
- generally increase of 10°c doubles the rate of reaction
8
Q
catalysts
A
- substance which can increase the rate of reaction without being chemically changed at the end of it
9
Q
characteristics
A
- small amount of catalysts can catalyse a large number of reactions
- highly specific in their actions
- mass remains unchanged before and after, although there may be a change in physical appearance
- small amount of impurities can prevent catalyst from working: catalyst posioning
- catalysts increase rate of reaction, NOT yield
10
Q
catalysts in industrial reactions
A
- haber process: iron
- reactions in catalytic converters: rhodium and palladium (and platinum)
- making margarine from vegetable oil: nickel
11
Q
enzymes
A
- a biological catalyst
- made of proteins
- highly specific in their actions
- can be denatured by high temperatures and extreme pH changes
12
Q
enzymes in reactions
A
- fermentation: enzymes in yeast
- oxidation of ethanol by air: enzymes in bacteria
