Rate Of Chemical Anatlsis

Question 1

Factors that effect rates of chemical reactions

Answer 1

o concentration
o pressure
o surface​ ​area
o temperature
o catalysts

Question 2

Collision theory

Answer 2

● Collision​ ​theory:​ ​chemical​ ​reactions​ ​can​ ​occur​ ​only​ ​when​ ​reacting​ ​particles
collide​ ​with​ ​each​ ​other​ ​and​ ​with​ ​sufficient​ ​energy
● Activation​ ​energy:​ ​the​ ​minimum​ ​amount​ ​of​ ​energy​ ​that​ ​particles​ ​must​ ​have​ ​to
react
● Increasing​ ​the​ ​concentration​ ​of​ ​reactants​ ​in​ ​solution,​ ​the​ ​pressure​ ​of​ ​reacting
gases,​ ​and​ ​the​ ​surface​ ​area​ ​of​ ​solid​ ​reactants​​ ​increases​ ​the​ ​frequency​ ​of
collisions​​ ​and​ ​so​​ ​increases​ ​the​ ​rate​ ​of​ ​reaction​.
● Increasing​ ​the​ ​temperature​​ ​increases​ ​the​ ​frequency​ ​of​ ​collisions​​ ​and​ ​makes​ ​the
collisions​ ​more​ ​energetic​,​ ​and​ ​so​ ​​increases​ ​the​ ​rate​ ​of​ ​reaction​.

Question 3

Catalysts

Answer 3

Catalysts​ ​are​ ​substances​ ​that​ ​speed​ ​up​ ​chemical​ ​reactions​ ​without​ ​being changed​ ​or​ ​used​ ​up​ ​during​ ​the​ ​reaction.
● Enzymes​ ​act​ ​as​ ​catalysts​ ​in​ ​biological​ ​systems
● Catalysts​ ​are​ ​not​ ​included​ ​in​ ​the​ ​equation​ ​for​ ​a​ ​reaction
● Catalysts​ ​decrease​ ​the​ ​activation​ ​energy; this​ ​increases​ ​the​ ​proportion​ ​of​ ​particles​ ​with energy​ ​to​ ​react.
● Catalysts​ ​provide​ ​a​ ​different​ ​pathway​ ​for​ ​a chemical​ ​reaction​ ​that​ ​has​ ​a​ ​lower​ ​activation energy

Question 4

Reverseable reactions

Answer 4

● If​ ​a​ ​reversible​ ​reaction​ ​is​ ​endothermic​ ​one​ ​way,​ ​it​ ​is​ ​exothermic​ ​in​ ​the​ ​opposite
direction.
● The​ ​same​ ​amount​ ​of​ ​energy​ ​is​ ​transferred​ ​each​ ​way​ ​(j

Question 5

Equalibrium

Answer 5

When​ ​a​ ​reversible​ ​reaction​ ​occurs​ ​in​ ​a​ ​closed​ ​system,​ ​equilibrium​ ​is​ ​reached when​ ​the​ ​reactions​ ​occur​ ​at​ ​exactly​ ​the​ ​same​ ​rate​ ​in​ ​each​ ​direction.

Question 6

The effect of changing conditions of on equilibrium

Answer 6

● The​ ​relative​ ​amounts​ ​of​ ​all​ ​the​ ​reacting​ ​substances​ ​at​ ​equilibrium​ ​depend​ ​on
the​ ​conditions​ ​of​ ​the​ ​reaction.
● If​ ​a​ ​system​ ​is​ ​at​ ​equilibrium​ ​and​ ​a​ ​change​ ​is​ ​made​ ​to​ ​any​ ​of​ ​the​ ​conditions,
then​ ​the​ ​system​ ​responds​ ​to​ ​counteract​ ​the​ ​change​ ​(Le​ ​Chatelier’s​ ​principle)

Question 7

The effect of changing concentration

Answer 7

If​ ​the​ ​concentration​ ​of​ ​one​ ​of​ ​the​ ​reactants​ ​or​ ​products​ ​is​ ​changed,​ ​the​ ​system
is​ ​no​ ​longer​ ​at​ ​equilibrium​ ​and​ ​the​ ​concentrations​ ​of​ ​all​ ​the​ ​substances​ ​will
change​ ​until​ ​equilibrium​ ​is​ ​reached​ ​again.
● If​ ​​concentration​ ​of​ ​reactants​ ​is​ ​increased​:​ ​position​ ​of​ ​equilibrium​ ​shifts
towards​ ​products​ ​so​​ ​more​ ​product​ ​is​ ​produced​​ ​until​ ​equilibrium​ ​is​ ​reached
again
● if​ ​​concentration​ ​of​ ​products​ ​is​ ​increased​:​ ​position​ ​of​ ​equilibrium​ ​shifts​ ​towards
reactants​ ​so​ ​​more​ ​reactant​ ​is​ ​produced​​ ​until​ ​equilibrium​ ​is​ ​reached​ ​again

Question 8

The effect of temp

Answer 8

If​ ​​temperature​ ​is​ ​increased​:​ ​equilibrium​ ​moves​ ​in​ ​the​ ​​direction​ ​of​ ​the
endothermic​ ​reaction​​ ​(e.g.​ ​if​ ​forwards​ ​reaction​ ​is​ ​endothermic​ ​and
temperature​ ​is​ ​increased,​ ​equilibrium​ ​shifts​ ​right​ ​to​ ​produce​ ​more​ ​product)
● If​ ​​temperature​ ​is​ ​decreased​:​ ​equilibrium​ ​moves​ ​in​ ​the​ ​​direction​ ​of​ ​the
exothermic​ ​reaction

Question 9

The effect of pressure

Answer 9

gaseous​ ​reactions,​ ​an​ ​increase​ ​in​ ​pressure​ ​will​ ​favour​ ​the​ ​reaction​ ​that
produces​ ​the​ ​least​ ​number​ ​of​ ​molecules​ ​as​ ​shown​ ​by​ ​the​ ​symbol​ ​equation​ ​for
that​ ​reaction.
● If​ ​​pressure​ ​is​ ​increased​:​ ​equilibrium​ ​shifts​ ​to​ ​​side​ ​of​ ​equation​ ​with​ ​fewer​ ​moles
of​ ​gas​ ​(e.g.​ ​N​2​​ ​+​ ​3H2​ ​​ ​​⇌​ ​​2NH​3,​ ​ ​left​ ​side​ ​has​ ​4​ ​moles​ ​of​ ​gas​ ​(1+3)​ ​and​ ​right​ ​has​ ​2 moles​ ​of​ ​gas.​ ​If​ ​you​ ​increase​ ​the​ ​pressure​ ​equilibrium​ ​moves​ ​right​ ​as​ ​there​ ​are fewer​ ​moles​ ​of​ ​gas​ ​on​ ​the​ ​right​ ​hand​ ​side,​ ​making​ ​more​ ​product)
● if​ ​​pressure​ ​is​ ​decreased​:​ ​equilibrium​ ​will​ ​shift​ ​to​ ​​side​ ​of​ ​equation​ ​with​ ​more moles​ ​of​ ​gas​​