Rates of reaction (not finished)

Required practical’s

The disappearing cross:

Using a measuring cylinder put 10cm3 of sodium thiosulfate solution into a conical flask

Place conical flask on a black cross

Add 10cm3 of hydrochloric acid into the conical flask

Swirl solution and start the stopwatch

Look down through the top of the flask , stop the clock when the cross can no longer be seen

Carry out again with lower concentrations of sodium thiosulfate solution

Repeat to calculate a mean

Problem : Different people have different eyesight and will be able to see the cross for longer than others

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Volume of gas produced:

Equation : magnesium + hydrochloric acid → magnesium chloride + hydrogen

We measure the amount of hydrogen gas produced

Use a measuring cylinder to place 50cm3 of hydrochloric acid into a conical flask

Attach conical flask to a bung and delivery tube

Place the delivery tube into a container filled with water

Place an upturned measuring cylinder also filled with water over the delivery tube

Add a 3cm strip of magnesium to the hydrochloric acid and start a stopwatch

The reaction produces hydrogen gas which is trapped in the measuring cylinder

Every 10 seconds measure the volume of hydrogen gas in the measuring cylinder

Repeat using different concentrations of hydrochloric acid

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Both of these experiments show us that the greater the concentration of a chemical in a reaction, the faster the reaction takes place, because this result it shown by two different experiments we can say that it is reproducible

Effects on rate of reaction

Surface area : More surface area to collide with so more frequent collisions

Temperature : Particles have more energy so the particles move faster, more frequent collisions, more successful collisions because more particles will have the activation energy

Increased concentration : More particles per unit volume, more frequent collisions

Catalyst : Lowers activation energy, Provides an alternative pathway, More successful collisions, catalysts do not get used up in a reaction