Rates Of Reaction (4) Flashcards
What are the 4 things that affect a rate of reaction
Temperature
Concentration (pressure for gases)
Catalyst
Size of particles / surface area
Rate of reaction equation:
Rate of reaction = Amount of reactant used OR amount of product formed / Time
What are the 3 ways to measure the speed of a reaction
Precipitation
Change in mass
The volume of gas given off
What is precipitation
When the product of the reaction is a precipitate which clouds over the solution
How to measure precipitation
Observe a marker and measure how long it takes to dissapear
How to measure change in mass
Do the reaction on a weight. The reaction has finished when the weight stops dropping. The quicker the weight drops, the quicker the reaction
When should you use the change in mass measurement
When a gas is produced
Which is the most accurate way to measure the rate of reaction
Change in mass
The third way - ‘the volume of gas given off’ involves the use of a gas ___________ to measure the volume of gas given off. The more gas given off during a time interval, the ___________ the reaction
Gas syringe
Faster
1 disadvantage of each method of measurement
Precipitation
Change in mass
Volume of gas given off
Precipitation: People may not degree when the marker disappears
Change in mass: Gas is released straight into the room
The volume of gas given off: If the reaction is too vigorous, you can easily blow the plunger out of the end of the syring
What does the reaction of hydrochloric acid and marble chips demonstrate the effect of
The effect of breaking the solid up into smaller bits
How to do the reaction of hydrochloric acid and marble chips
Fill a flask with hydrochloric acid and connect it to a delivery tube to another upside-down measuring cylinder in a trough of water. Drop marble chips in a solution of hydrochloric acid and start the timer immediately. The Co2 given off will create bubbles. You can measure the co2 given off by finding the difference between the water before and after Do the same experiment again with the same mass of marble chips but crush them up more, or change the temperature. See the difference.
Good experiment to show the effect of catalysts
The decomposition of hydrogen peroxide
How to do the decomposition of hydrogen peroxide to prove the effect of catalysts.
Hydrogen peroxide decomposes to form heavy water and oxygen. This is normally a slow reaction but manganese oxide speeds it up
Since oxygen is the gas given off you can just use a syringe to measure it
What does a rate of reaction graph look like
This
What is collision theory
The theory that a rate of reaction simply depends on how often and how hard the reacting particles collide with each other.
How does higher temperature effect the rate of reaction
When temperature is increased, particles have more energy and move quicker meaning that they will collide more frequently.
How does concentration effect the rate of reaction
If a solution is made more concentrated it means there are more particles of reactant around. Which makes collisions more likely.
How does pressure effect the rate of reaction
In a gas, increasing the pressure means the particles are more squashed together together (compact) so they are going to collide more frequently.
How does larger surface area effect the rate of reaction
If the surface area is increased then the particles around it that want to react have more area to react with, hence, more succesful collisions.
How does a catalyst effect the rate of reaction
A catalyst works by giving the reacting particles a surface to stick to which increases the number of succesful collisions by lowering the activation energy
The initial energy is known as the _______________ energy and it’s needed to break the initial bonds
Activation energy
Energy must be supplied to break existing bonds - so bond breaking is an ______________ process
Endothermic
Energy is released when new bonds are formes - so bond formation is an __________________ process
Exothermic
