C4 how changing a variabel changes the rate of reaction

what is the independent variable

the change, change of concentration of hydrochloric acid

what is the dependent variable

measure, measure time

what is controlled variable

same , sue same volume of solution same mass of magnesium same temp

Apparatus and chemicals

• 200 cm³ of 2 mol/dm³ hydrochloric acid and deionised water

• 10 x 3 cm strips of magnesium

• 100 cm³ beaker, 250 cm³ beaker, watch glass, measuring cylinder (25 cm³)

• Stop clock

Method

1. Carefully collect 200 cm³ of hydrochloric acid using the 250cm³ beaker, and 10 strips of magnesium using a watch glass.

2. Using the measuring cylinder, measure out 25 cm³ of hydrochloric acid and add to the small beaker. Remember to use the measuring cylinder accurately.

3. Drop the piece of magnesium ribbon into the beaker and start the stop watch, swirl once to ensure the magnesium is fully coated in the acid. Stop the watch when all the magnesium disappears.

4. Repeat the experiment to ensure reliability of results.

5. Repeat steps 2-4 except using a total of five different volumes of acid and water to ensure different concentrations of acid. The proportions you need to use are given in the results table:

Rate equation

Rate = 1 / time (for reaction to complete) - units is s^-1

effect of increasing concentration (e.g an acid)

more particles present in the same volume of liquid

increased number of successful collisions

increased rate

effect of increasing surface area

there are particles on the surface exposed

there are more successful collisions (with activation energy) between particles in a given time

the rate of reaction is faster

effects of temperature using collision theory

particles are moving faster, so there are more frequent colissions

particles have more (Kinetic) energy, so more of rthe particles have the activiation enegry and react when they collide

there, there are more sucessfuk colissions between particles in a given time

the rate of reaction is faster.