Flashcards in Rate Of Reaction Deck (11):
When the temperature is increased, the particles all move faster, if they are moving faster they collide more frequently. Also the faster they move the more energy yet have, so more of the Collins will have enough energy for the reaction to take place
Increasing the concentration of pressure
If a solution is made more concentrated, it means there are more particles knocking about in the same volume of water (or other solvent).
Similarly, when the pressure of a gas is increased, it means that the same number of particles occupies a smaller space. This makes collisions between the reactant particles more frequent
Increasing surface area
If one of the reactants is solid, then breaking it up into small pieces will increase its surface area to volume ratio. This means that for the same volume of the solid, the particles move around it will have more area to work on so there will be collisions more frequently
Using a catalyst increases the rate
A catalyst is a substance that speeds up a reaction without being used up in the reaction itself. They decrease the activation energy needed for the reaction to occur. They do this by providing an alternative reaction pathway with a lower activation energy
Equation go work out mean rate of reaction
Rate of reaction = amount of reactant used or amount of product formed / time
Measuring rate of reaction - colour change the disappearing cross
You can record the visual change in a reaction if the initial solution is transparent. You can observe a mark through the solution and measure how long it takes for it to disappear using a stop watch - the faster the mark disappears the quicker the rate of reaction.
Measuring rate of reaction - change in mass
Measuring the speed of a reaction that produces a gas can be carried out using a mass balance. As the gas is released the mass disappearing is measured on the balance. The quicker the reading on the balance drips the faster the reaction. Take measurements at regular intervals to plot a gaff. This is the most accurate of the three measurements as the mass balance is very accurate
Measuring rate of reaction - the volume of gas given off
This involves the use of a GAS SYRIGE, to measure the volume of gas given off. The more gas given of during a given time interval the faster the reaction. Accurate as gas syringes normally give volumes to nearest cm3.
PRACTICAL - magnesium and hydrochloric acid to produce hydrogen gas
1) start by adding a set volume of hydrochloric acid to a CONICAL FLASK and carefully place on MASS BALANCE.
2) now add some magnesium ribbon to the acid and quickly plug the flask with a bung or cotton wool this lets the gas escape but stops acid spitting out
3) start the STOPWATCH and record the mass on the balance . Take reading of the mass at regular intervals
4)plot results on graph
5)repeat with more concentrated acid solutions . Variables such as the amount of magnesium and volume of act used should be kept the same each time only change the acid concentration .
You could also measure gas released using gas syringe
What is equilibrium?
Rate of forward reaction equals the reverse reaction