metal displacement

7/31/2019 Metal Displacement

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Concept Experiment

Interpret Data Evaluation


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K +Na+

Ca+2

Mg+2 Al +3 Zn+2 Fe+2 Sn+2 Pb +2

H+ Cu+2 Hg+2 Ag+

Au+

M

O

R

E

E

L

E

C

TR

O

P

O

S

IT

I

V

E


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ELECTROCHEMICAL SERIESCation

K +Na+

Ca+2

Mg+2 Al +3 Zn+2 Fe+2 Sn+2 Pb +2 H+ Cu+2 Hg+2

Ag+

Au+

The MORE electropositivemetal is able to displacea LESS electropositive metalfrom its salt solution


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Concept:

Zinc

Copper(II) sulphate solution(Salt solution)

Brown solid

Note: Salt solution: sulphate / nitrate/ chloride / carbonate*


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Zinc is higher than copper in ECS Zinc is able to displace copper from

copper(II) sulphate solution

Chemical Equation:

Zn + CuSO 4 ZnSO 4 + Cuatom ion

ion

atom


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Before Reaction

Zn

copper(II) sulphate solution

Cu+2

Cu+2

Zn

Zn


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After reaction

Zinc dissolved

[ atom change to ion]

Copper(II) sulphate solution

Brown solid[ ion change to atom]

Zn2+

Zn+2

Cu

Cu

Blue solution change toColourless

[ concentration of Cu2+

ion decreased]


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Chemical Equation:

Zn + CuSO 4 ZnSO 4 + Cuatom ionion atom

HALF Equation:Zn Zn 2+ + 2e

Cu 2+ + 2e Cu

IONIC Equation:

Zn+ Cu2+

Zn2+

+ Cu


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But..

When copper is put in zinc sulphatesolution,

There is No change??????? Copper try to displace zinc

But Cu is lower than Zn is ECS Cu is not able to displace zinc .


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How can we construct theelectrochemical series based on the

displacement of metals ?

Idea :If metal X is able to displace metal Y from Y chloride solution,SoX is more electropositive than YOr

X is higher than Y in the ECS


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How can we know that displacementreaction takes place ?.

When you can observe these changes :New solid depositedSolutions colour changed Metal used dissolved / thinnerTest tube feels hot


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Data & Observation

Metal Coppernitrate

Leadnitrate

Zincnitrate

Magnesiumnitrate

copper

Lead

Zinc

Magnesium


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Metal Coppernitrate

Leadnitrate

Zinc nitrate Magnesiumnitrate

Copper X X x

Lead Leaddissolved/brown S

x X

Zinc ZincdissolvedOR brownsolid

Zincdissolved/ Grey S

X

Magnesium Mgdissolved/Brown S

Mgdissolved/Grey S

Mgdissolved/Grey S


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1. Magnesium is able to displace copper, lead and zincSomagnesium > coppermagnesium > leadmagnesium > zinc

Interpret the data

1. Zinc is able to displace copper, lead and zincSomagnesium > coppermagnesium > leadmagnesium > zinc


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Conclusion

Arrange the metals in descending order

of tendency to release electron is :

Mg > Zn > Pb > Cu


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Equation

Metal Solution Half Equation

Zinc Leadnitrate

Ionic Equation

Zn Zn+2 + 2e

Pb+2 + 2e Pb

Zn + Pb+2 Zn+2 + Pb

Zinc become thinner / dissolvedGrey solid deposited


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Test yourself.. Put a copper strip into a test tube

contains silver nitrate solution. State the observation

Write the half equations

Silver nitrate solutioncopper


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1. Predict whether take

A. Ada tindak balas

B. Tiada tindak balas


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Manakah antara berikut mewakili setengahpersamaan bagi tindak balas yang berlakudalam tabung uji itu.

A. Pb+2 + Zn Pb + Zn+2

B. Pb + Zn+2 Pb +2 + Zn


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B. Pb + Zn+2 Pb +2 + Zn


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B. Pb + Zn+2 Pb +2 + Zn


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ELECTROCHEMICAL SERIES

Themoreelectropositive

metal is able todisplace thelesselectropostivemetal from itssalt solution

K +Na+ Ca+2 Mg+2

Al +3

Zn+2

Fe+2 Sn+2 Pb +2 H+ Cu+2 Hg+2

Ag+ A +

metal displacement

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