spd of reaction Flashcards
fast vs slow reaction egs
fast reaction
neutralisation
slow reaction
rusting
define marble chips
calcium carbonate
limestone
CaCo3
methods for measure rate of reaction
- loss in mass, balance
- use a gas syringe
- water displacement (count volume not bubbles)
- KI turn, colourless -> brown
when using loss of mass method must…
tare electronic balance
why loss in mass method always decrease in mass
() gas escaped
cotton wool in setup is porous
purpose of cotton wool in loss of mass method
- cotton wool porous, allow () gas escape, result loss of mass
- efferverscence, acid + () reaction, acid may leave conical flask, acid spray
- prevent mass decrease due to acid spray
- inaccurate result
loss of mass method
what data to collect
mass of mixture in fixed time interval
measure rate of reaction
reaction nvr produce gas, only produce precipitate
use aq. potassium iodide
which reaction
as time passes by, rate of reaction decreases
neutralisation
5 things that can change rate of reaction
- particle size
- concentration/number of particles per unit volume
- pressure
- temperature
- catalyst
When limting reactant added, increase yield.
1, 2, 3 -> increase freq of collision
5 -> increase freq of effective collision
does increase of mass and volume change rate of reaction?
no
collision theory
- for reaction to take place
- particles must collide with sufficient energy
- reach activation energy
https://docs.google.com/document/d/1Ep_FO9CxYSFbxmf3Zqg9mgm9NNyt2enpfMDr49gufrU/edit?tab=t.0 page 22
what is effective collision
collision theory
new products are formed
i.e.
AA + BB -> AB + AB effective
AA + BB -> AA + BB ineffective, no reaction occured, no new product formed
how particle size affect rate of reaction
- particle size, solid reactant decreases, increases SA:Vol ratio, reactants
STANDARDISED
2. increase rate of collision
3. increase freq of effective collision, reactant particles
4. rate of reaction increase
how higher conc. of particles affect rate of reaction
- more particles per unit volume
- distance btwn particles shorter
- collisions, proportional 2 no. particles present
- increase rate of collision
- increase freq of effective collision
- rate of reaction increase
When limiting reactant added, yield increases
how higher pressure affect speed of reaction?
- pressure only affect reactions involving gases
- higher pressure, greater number of reacting particles per unit volume
- increase rate of collision
- increase freq of effective collision, reactant partcles
- increase rate of reaction
how catalyst affect speed of reaction
provide alternative pathway for reaction w/ lower activation energy
how temperature affect speed of reaction
- temp, reaction increase
- reacting particles gain kinetic energy, move faster
- particles collide w/ each other more, freq of collisions increase
- proportion of particles, kinetic energy overcome Activation Energy increase,
- freq effective collision increase
- rate of reaction increase
- small increase temp can mean large increase, rate
this is best factor to increase spd of reaction
- increase freq of collision
- increase rate of effective collision
- can be used, all 3 states
decrease particle size -> increase spd of reaction
which state can use?
solid
increase conc -> increase spd of reaction
which state can use?
aq/soln.
increase pressure -> increase spd of reaction
which state can use?
gaseous
catalysts
characteristics
- can change in states aft reaction (phys)
- increase rate of reaction, not yield
- specific in action, diff catalyst for diff reactions
- req in small amt → not used up, reaction
- effectiveness hindered by impurities
rest from bio
- remain chemically unchanged aft chemical reaction
- specific in (their reactions)
volume of product produced // time graph
gradient of graph represent…
rate of reaction
e.g. catalysts
Fe -> making ammonia
Pt (Platinum) -> making HNo3
Pd (Palladanium)
e.g. biological catalysts
bacteria spd up manufacture cheese bread
why rate of reaction slow down as time passes?
- reactants are being used up,
- conc. of reactants are decreasing with time
what is yield in a reactant released plotted against time graph?
reactant released
why collision unsuccessful
particles did not collide with sufficient energy, reach Ea
why increase rate of reaction
- economic interest
- higher rate, production
- more efficient, sustainable
aq/gaseous reactants approx. ___deg celc increase, rate of reaction x2
10
desc graph
increase all 4 factors (except particle size)
- particle size
- concentration/number of particles per unit volume
- pressure
- temperature
- catalyst
- compared to reaction w/ (decreased pressure/temp),
- graph for same reaction w/ (increased pressure/temp),
- steeper gradient, start, horizontal sooner
steeper gradient: increased rate of reaction. Yield does NOT increase.
horizontal sooner: (limiting) reactant particles completely used up in reaction quicker
ALWAYS WRITE FOR ENZYMES
remain chemically unchanged after reaciton
when measuring gas periodically, must add
measure volume of gas (left/released)
how to make experiment, decide effect of (factor) on rate of reaction
- record time taken for (5(u) gas collected/lost/indicator color change),
- increasing (factor) when repeating exp.
increase conc. always increase rate?
no. e.g.
zero order rate reactions
water displacement measure gas full exp.
- Add (soln.) conical flask
- Use delivery tube -> connect flask, upside down measuring cylinder in trough, water
- Add (solid + catalyst, if needed) -> conical flask, quickly put bung back, flask
- Measure, volume of gas produced, fixed time (using measuring cylinder)
- Repeat with (change varia)
add KI measure spd of reaction full exp
- add (soln.) to (soln.) in conical flask w/ KI, start timer
- look down from above see X, stop timer, X no longer visible, record time
