Determining the position of unknown element X in the Reactivity Series Free Essay Example

To determine the position of Element X in the reactivity series

Hypothesis

The reactivity series is the arrangement of elements according to their reactivity. The most reactive element is placed at the top and the least reactive at the bottom. The elements at the top can displace elements below them from their compounds

In the experiment, element X will either have elements more reactive or less reactive or both. Based on this, the position of the unknown element can be found out.

Assuming that the element given is not potassium, then potassium will displace X from its compound; thus we can say that potassium is more reactive than X; and X is below potassium in the reactivity series. Assuming that copper is less reactive than X; X will displace copper from its compound. This means that X is higher than copper in the reactivity series than copper.

In the experiment, the enthalpy (temperature) change will also show how reactive element X is.

For example if X is right above Zinc in the reactivity series i.e. element X is aluminium, then the temperature difference between reacting Al with CuSO4 will be more than reacting Al with ZnSO4 or FeSO4. This is because as the distance (number of elements in between between) the elements increases there is more difference in the reactivity level of the selected elements.

When ?H (?Heat) is +ve, the reaction taking place is exothermic and when ?H is -ve, the reaction will be endothermic. When the number of element between the elements reacting is more, then ?H of the reaction will also be more.

For example if we take Zinc as element X, then Zinc is more reactive than Lead; but Zinc is even more reactive than Copper. This is because Copper is further below Lead in the reactivity series. Thus a reaction between Zinc and a Copper compound will be more reactive (& will have a higher ?H) than a reaction between Zinc and Lead.

When ?E (?Energy) is +ve, the reaction taking place is endothermic and when ?E is -ve, the reaction will be exothermic. The reason behind the nature of ?H stated previously is the ?E (?Energy) of the reaction. Again; more the number of elements between the reactants (according to the Reactivity Series) the lower the value of ?E i.e. more exothermic the reaction is. This is due to the type of bonds present in various compounds. Taking the pervious example, a reaction between Zinc & a Copper compound will give a lower ?E than a reaction between Zinc & a Lead compound. Thus such reactions are more apparent.

Variables

Independent

The Metal Compound used to react with Element X

The metal compound used to react with Element X was varied as this variation of the metal will help us determine the position of element X.

Dependent

Whether a reaction takes place or not

When different metal compounds are used, it is not necessary that a reaction takes place every time. The occurrence of a reaction depends on the metal present in the compound used.

Energy Change (?E)

?E depends on the compound used. In different compounds there are different types of bonds present and also every bond has a different energy level.

Enthalpy Change (?H)

?H depends on ?E. If ?E is -ve, then the reaction is exothermic; if ?E is +ve, then the reaction will be endothermic.

Controlled

Volume of the Metal Compound taken

The volume of the metal compound taken must be kept constant as varying volumes can affect the final temperature.

Size of Element X strip

The size of the strip of Element X must also be kept constant as varying lengths can again affect the final temperature.

Apparatus

1 Strip of Element X

7 Test tubes

5ml of CuSO4

5ml of FeSO4

5ml of MgSO4

5ml of PbNO3

5ml of KSO4

5ml of AgNO3

5ml of ZnSO4

Procedure

1. Take a strip of Element X and cut it into 7 equal pieces

2. Pour 5ml of CuSO4 into a test tube

3. Put a thermometer into one test CuSO4 and measure the temperature

4. Now put a piece of Element X into the test tube and measure ?H

5. Repeat Steps 3 & 4 for FeSO4; MgSO4; PbNO3; KSO4; AgNO3 & ZnSO4

Diagrams

Results

Compound

Reaction

Initial Temperature (�C)

Final Temperature (�C)

?H (�C)

KSO4

No

21

21

0�

MgSO4

No

21

21

0�

ZnSO4

No

22

22

0�

FeSO4

No

21

21

0�

PbNO3

Yes

21

22

2�

CuSO4

Yes

22

25

3�

AgNO3

Yes

21

26

5�

Graph

Discussion

The strip of element X given to us was shiny, this indicates that element X is not very reactive. Reactive metals such as aluminium usually form a metal oxide layer on top of them thus losing their luster. When Element X was put in sulphate of potassium (which is a clear solution), the solution remained clear, and the piece of Element X also remained shiny; thus indicating no reaction. Element X behaved similarly for sulphates of Magnesium, Zinc & Iron.

A piece of Element X into PbNO3, after a lot of time, the solution started to become cloudy (white precipitate), indicating a reaction. In this reaction the ?H was +1�C.

In CuSO4, the piece of Element X was deposited with black precipitate all over. Also the solution becomes lighter blue as compared to the pure CuSO4(aq). It was a very slow process.

In AgNO3, the solution turned cloudy (black) immediately after suspending the piece of Element X.

If we observe the table below carefully, we notice that Element X did not react with K, Mg, Zn and Fe. But it reacted with Pb, Cu & Ag. This means that element X is Sn; because the reactivity series goes as follows: K, Na, Ca, Mg, Al, Zn, Fe, Sn, Pb, Cu, Ag, Au.

Compound

Chemical Equation

Energy Equation

?E

KSO4(aq)

–

–

MgSO4(aq)

–

–

ZnSO4(aq)

–

–

FeSO4(aq)

–

–

Pb(NO3)2(aq)

CuSO4(aq)

AgNO3(aq)

As I stated in my hypothesis, that the further apart the elements are (in the Reactivity Series) the lower the ?E is. This means that the reactions are more apparent (vigorous) and also more heat is produced in such reactions.

Conclusion

From this experiment, I conclude that the Element X given to me is below Iron and above Lead in the reactivity series i.e. the element is Tin. I also conclude that the further apart the elements are (in the Reactivity Series) the higher the ?H and lower the ?E. I also conclude that such reactions are more reactive (apparent) as compared to those between element with a lower number of elements between them.

Evaluation

In this experiment, if the mass of element X would have been measured and then used for reactions the reactions would have been more accurate and reliable.