Find the concentration of the unknown acid using Mg strips.

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- Megan Andrews - Mrs. Ball - Chemistry Coursework - 09/04 - 11 Alpha -

-Investigation: Find the concentration of the unknown acid using Mg strips-  

Aim:

My aim is to find out the concentration of the unknown acid marked X, using magnesium strips and various concentrations of hydrochloric acid to compare results.

Outline:

This section will outline the main idea for how to solve the problem. This will be based on scientific knowledge and understanding.

We have been supplied with hydrochloric acid, which has a concentration of 2 moles per decimetre cubed (2 mol/dm3). We also have been provided with a length of magnesium ribbon. Another bottle of hydrochloric acid, but this time with an unknown concentration, is named X. The concentration of X is known to be between 0.5 mol/dm3 and 2 mol/dm3. Using only these chemicals, our task is to find out the concentration of the unknown acid. We are allowed to use any equipment or other apparatus, which is normally available in the laboratory.

To work out how to change the concentration of solutions, we will use a certain method. Many chemical reactions are carried out in solutions. Concentration is measured in moles per decimetre cubed, mol/dm3. A mole is a measure of amount of substance.

1 dm3 = 1000 cm3

To provide a difference in concentration, a 2-mol/dm3 solution will need to be diluted.

For instance, if we were to take 50 cm3 of acid and 50 cm3 of water, we would work out the new concentration as follows:

Volume of acid taken                x        Original concentration

Total volume of solution

So the new concentration would be:

50                x                1 mol/dm3

100

The collision theory describes the way temperature, concentration and surface area of the solid reactant affects the rate of reaction, by affecting collisions between particles. Particles react when they collide with sufficient energy. At a higher temperature collisions are more frequent, and they also have more energy, both because particles are moving faster. At a higher concentration collisions are again more frequent, as there are more reactant particles in the liquid. Increased surface area of the solid again increases the frequency of collision between reacting particles, as the liquid reactant has greater contact with the solid one. Adding a catalyst can also increase rate of reaction, but there is not one for this reaction.

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- Megan Andrews - Mrs. Ball - Chemistry Coursework - 09/04 - 11 Alpha -

-Investigation: Find the concentration of the unknown acid using Mg strips-

It is necessary that all these factors be applied to my results. For instance, the length of magnesium strips should be taken into consideration, because if the length is 5 cm, then it may take a very long time for the whole thing to dissolve in a weak solution, which will be waste of lesson time.

Using this theory, I predict that the higher the concentration, the faster the magnesium strips will dissolve.

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