C6 - chemical reactions (changes, rate of reactions, redox) Flashcards
things needed for a reaction
particles need to collide with enough energy to start a reaction
ways to measure rate of reaction
-loss of mass
-volume of gas produced
formula for average rate of reaction
-total mass lost/ time
why does rate of reaction decrease after 50%
-there are less reactant particles
define activation energy
The minimum energy colliding particles require to react
define successful collision
-collisions with enough energy to react
define limiting reactant
reactant that is used up first in a reaction
what affects rates of reactions
-temp
-concentration
-pressure of gas
-Surface area of solids
-catalysts
conclusion for temp.
-more kinetic energy
-more movement
-more frequent
-more successful collision
-faster rate of reaction
does concentration affect activation energy
no
how to increase concentration
-increase no. particles
-decrease volume
conclusion for concentration/ pressure
-more concentration
-more particles per unit volume
-more frequent collisions
-increased rate of reaction
NO ENERGY CHANGE
relationship of Surface area & particle size
-more surface area
-smaller particle size
conclusion of surface area
-smaller particle size
-more surface area exposed to react
-more frequent collisions
-increased rate of reactions
NO ENERGY CHANGE
define catalyst
-substance that speeds up the rate of a reaction but is unchanged at the end of the reaction
what does catalyst do to activation energy
-lower activation energy
conclusion of catalysts
-increase rate of reaction
-by lowering activation energy
-by providing an alternative reaction pathway
-more successful collisions - greater proportion of particles with energy above the activation energy
more successful collisions or more frequent collisions
-temp = more frequent & successful collisions
-concentration = more frequent collisions
-surface area = more frequent collisions
-catalyst = more successful collisions
how to find rate of reaction on graph
-make a tangent
-draw lines extending from tangent - make a triangle
-find gradient
-ans can vary
define anomaly
result that doesn’t fit the pattern
how to write a conclusion
-describe results
-explain - why
note: oxidation & reduction always go tgt
define spectator ion
-ion that doesn’t change in a reaction
diff. in numbering of oxidation state & ionic
oxidation state - +2
ionic - 2+
rules:
-all elements oxidation state = 0 - electrically neutral
-rmb charges for some compounds - eg, SO4 = -2
-H oxidation state = +1
-O2 oxidation state = -2
-a compound oxidation state total = 0
OILRIG
-Oxidation Is Loss of electrons
-Reduction Is Gain of electrons
reduction things
-loss of oxygen
-gain of electrons
-gain of hydrogen
-oxidising agent
oxidation things
-gain of oxygen
-loss of electrons
-loss of hydrogen
-reducing agent
ionic half equations
-find oxidising & reducing agents
Reactants -> Prodcuts
- _a__ -> ___ + ____e (a is oxidised)
- _a__ + ____e -> _____ (a is reduced)
-electrons in both are the same
ionic equations
-rewrite half equations
-cancel electrons from both sides
