Rate Of Reaction Flashcards
How can we use a precipitates to determine the rate of reaction?
This is when the product of a reaction is a precipitate which clouds the solution
We can observe a mark through a clear solution and measure how long it takes for the mark to disappear
Give an example experiment of a precipitate reaction
React the clear solutions of sodium thiosulfate and hydrochloric acid together. This forms a yellow precipitate of sulphur
The experiment involves watching a black mark disappear through cloudy sulphur and timing how long it takes to go with a stopwatch
The reaction can be repeated for solutions at different temps( using a water bath to heat both solutions to the desired temperature)
Control: volume and concentration of solutions
What is the rate of reaction?
How fast reactants turn into products
What does the rate of reaction depend on?
Temperature
Concentration
Surface area
Catalyst
Why does temperature increase the rate of reaction?
Particles gain energy energy and move more quickly
Particles collide more often
So greater chance of successful collisions
Why does an increased concentration in solutions increase the rate of reaction?
More particles( of the reactants) are moving around the same volume of solution. So the reactant particles are more 'crowded' together Therefore the reactant particles are likely to collide more frequently.
( same with gas only now there are more gas particles in a given space etc….)
Why does a larger surface area increase the rate of reaction?
If the surface in question was a solid, breaking it into pieces increases the total surface area
So particles around it( in the solution) will have a greater area to work on
Therefore there will be more frequent collisions as there are more particles( of the surface) exposed to attack.
What is the activation energy?
The smallest amount of energy that particles must have before they react.
What are catalysts?
Substances that increase the speed the rate of reaction
Without being chemically changed or used up in the reaction
Only need a tiny bit to catalyse huge reactions
Why are catalysts usually in the form of pellets?
Give them the biggest possible surface area.
How do catalysts work?
A catalyst increases the number of SUCCESSFUL collisions
It works by giving the reacting particles a surface to stick to where they can bump in to each other
It reduces the activation energy needed by particles before they react
Why are catalysts useful in industry?
Catalysts increase the rate of reaction which saves a lot of energy and consequently money because the plant doesn’t have to operate as long to produce the same amount of product
What are the Advantages and disadvantages of catalysts
Can allow reactions to work at lower temperature
So less energy used
So conserves fossil fuels and saves money
Disadvantages:
They are very expensive to buy and often have to be removed from the product of the reaction and cleaned from it
Different reactions use different catalysts, so if businesses make more than one product they’ll need multiple catalysts
Poisoned by impurities and easily stop working.
What are Exothermic reactions?
Exothermic reactions are reactions that transfer energy to the surroundings
They are indicated by a temperature rise.
Some examples see combustion and neutralisation reactions( acid and alkali)
Many oxidation reactions are exothermic like like respiration
Used in hand warmers( oxidation of iron) and self heating cans( calcium oxide and water to make calcium hydroxide)
What are endothermic reactions?
Endothermic reactions are reactions that take in energy from the surroundings
Indicated by a fall in temperature
Examples are thermal decomposition reactions
E.g calcium carbonate
They are also used in a more domestic setting, e.g sport injury packs( take heat in and become very cold)
