Measuring Rates of Reaction Flashcards
What are the Units of amount of reactant used or amount of product formed?
gas = cm3
solid = g
Time = s
moles
What are the Units of the rate of a reaction?
cm3/s
g/s
mol/s
What is the 1st way of measuring Rates of Reaction?
Precipitation and Colour Change
Record Visual Change in a reaction if initial solution is transparent and the product is a precipitate which clouds the solution (it becomes opaque)
Observe a mark through the solution and measure how long it takes for it to disappear - the faster the mark disappears, the quicker the reaction.
If reactants are coloured and the products are colourless (or vice versa), you can time how long it takes for the solution to lose (or gain) its colour.
Results are very subjective - different people might not agree over the exact point when the mark ‘disappears’ or the solution changes colour.
What is the second way of Measuring Rates of a Reaction?
Change in Mass (usually gas given off)
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 drops, the faster the reaction
If take measurements at regular intervals, you can plot a rate of a reaction graph and find the rate quite easily.
What is the 3rd way of Measuring Rates of Reaction?
The Volume of gas given off
This involves the use of a gas syringe to measure the volume of gas given off.
The more gas given off during a given time interval, the faster the reaction.
Gas syringes are quite accurate. You can take measurements at regular intervals and plot a rate of reaction graph using this method too. You have to be quite careful though - if the reaction is too vigorous, you can easily blow the plunger out of the end of the syringe.
