Measuring rates of reaction Flashcards
What units are usually used to measure a gas?
cm^3
What units are usually used to measure a solid?
grams
What other unit could you measure the amount of product or reactant in?
moles
How can you say the cloudiness of a solution changes?
It’s turbidity changes
What is required of the solution and product of the reaction in order to record the visual change?
The initial solution nedds to be transparent and the product, needs to be a precipitate which clouds the solution (causes it to become opaque)
How can you measure the rate of reaction by precipitation and colour change?
1.You can observe a mark through the solution and measure how long it takes for it to disappear –> the faster the mark disappears, the faster the reaction.
2. If the reactants are coloured and the products are colourless (or vice versa) you can time how long it takes for the solution to lose/gain its colour
What faults are there with this method?
The results are subjective. There could be differences of opinion over the exact point when the mark disappears or the solution changes colour. Also, using this method you can’t plot a rate of reaction graph from the results.
How can you measure the rate of reaction by change in mass?
1.Measuring the rate of reaction that produces a gas can be carried out using a mass balance.
2. Start the timer and, as the gas is released, the mass disappearing is measured on the balance.
3. The quicker the reading on the reaction drops the faster the reaction
What do you need to do to plot the reaction graph?
Take measurements at regular intervals. By doing this, you can also find the rate quite easily.
What is the change in mass usually due to?
Gas given off
What are the advantages and disadvantages of the change in mass method?
It’s the most accurate of the 3 methods described coz the mass balance is very accurate.
The disadvantage of releasing the gas straight into the room.
How can you measure the rate of reaction by the volume of gas given off?
You need to measure the amount of gas in the syringe. The more mass given of during a given interval of time, the faster the reaction.
What equation would be used in this experiment?
(amount of reactant formed) / (time taken)
What piece of equipment is needed for this?
A gas syringe and a beaker.
What are the advantages and disadvantages of this method?
Gas syringes usually give volumes accurate to the nearest cm^3 so they’re quite accurate. You can also plot a rate graph by taking measurements at regular intervals too.
However, if the reaction is too vigorous you can easily blow the plunger out the end of the syringe, so safety precautions are needed.
