redox module 3 word 97
DESCRIPTION
TRANSCRIPT
Question 1
a) State the conditions for the rusting of iron
i) …………………………………..ii)……………………………….
b) What is the meaning of corrosion of metals?
………………………………………………………………………………………
Write a half equation for corrosion of zinc metal ………………………………..
c) Can corrosion of zinc be called rusting of zinc? Explain
1
NAME………………………………………..CLASS………….TEACHER………………
KNaMgAlZnFeSnPbCuHgAgAu
……………………………………………………………………………..
d) Iron rusts faster at places near the sea. Explain
……………………………………………………………….
e) In the diagram to the right are the metals arranged in descending order in electrochemical series. Gold when left for a long time does not corrode , whereas magnesium corrodes easily. Explain.
………………………………………………………………………..
f) Aluminum is situated high in the electrochemical series. But aluminum is very resistant to corrosion as compared to iron. Explain
………………………………………………………………………………..
Fill in the blanks with suitable words
2
Step 1 (Oxidation)The surface of iron in the middle of water droplet serves as the anode, where oxidation occurs.
a) What happens to the iron atom here?
……………………………………………………………….
b) Write the half equation for the reaction that occur in a) above
…………………………………………………………………………………
c) Through what substance do the electrons move to? ………………………
d) Through what substance do the iron(II) ions move to? ……………………….
Step 2 (Reduction) the Iron surface serves as cathode where reduction occur
e) Where do the electrons that are released by iron flow to? And why?
3
………………………………………………………………………………f) What happens to the electrons here?
…………………………………………………………………….g) Write the half equation for the reaction that occur
……………………………………………………………………h) Where do the hydroxide ions formed in this reaction go to?
…………………………………………………………………………
Step 3 Formation of Voltaic Cell)
a) What happens to the iron(II) ions and the hydroxide ions formed from step 1 and step 2?
…………………………………………………………………………
b) Write the ionic equation for the reaction
………………………………………………………………………….
c) A voltaic cell is formed in this mechanism of rusting. State 2 process that produce this voltaic cell
i) Through the metal …………………………………………………
ii) Through the water …………………………………………………..
Step 4 Formation of rust
a) What happens to the iron(II) hydroxide formed when exposed to oxygen?
…………………………………………………………………………b) Write the formula of the rust formed
………………………………………………………………………….c) State the oxidizing agent and the reducing agent in rusting mechanism
……………………………………………………………………………..
4
Fill in the table below . You may choose answers from the box given
Ways to control rusting
Methods Where are the method used?
1 Using protective coating
Covering with paint
2 Covering with oil and grease
3 Covering with tin(tin plating)
4 Covering with chromium(chromium plating)
5 Covering with zinc metal(galvanizing)
6 Sacrificial protection
Using blocks of zinc metal
7 Using blocks of magnesium metal
8 Alloying Making stainless steel(alloy)
5
Iron and steel objects, like motorcars, ships, bridges and steel pipes
In machinery
Cans of food
Bumpers of motorcars
Roofs of housesBlocks of zinc are attached to the hull of the ship
To protect underground steel pipelines
Knives, spoons, medical instruments, kitchen sinks
An experiment was done in a lab to investigate factors that affect rust. All the boiling tubes were left for 3 days
a) After 3 days, it was noticed that in boiling tubes C and D, the potassium hexacyanoferrate(III) solution changed colour to dark blue. What is the inference?
……………………………………………………………….b) In which boiling tubes did iron nails show rusting?
…………………………………………………………..c) The nails in boiling tubes A and B did not rust. Explain
…………………………………………………………………d) Explain the function of experiment in E
……………………………………………………………………..
e) Write half reaction for
i) Oxidation in experiment A …………………………………….
ii) Oxidation in experiment C ……………………………………
6
iii) Oxidation in experiment E ……………………………………
f) What type of metals prevent rusting of iron? …………………………..
g) What type of metals encourage rusting of iron?..............................
h) If iron nails are immersed in alkaline solution, the nails do not rust. Explain
……………………………………………………………………….
i) Calcium is more effective than zinc to prevent rusting
Why do you think steel objects are coated with zinc instead of calcium?
………………………………………………………………………….
j) Explain the followings
i) When a metal corrodes, it undergoes oxidation
…………………………………………………………………
ii) In tin plating, iron can is coated with tin. However as soon as the can is scratched, rusting will occur quickly
……………………………………………………………………….
iii) In galvanizing, iron is coated with a layer of zinc. When the galvanized iron is scratched, rusting does not occur.
7
……………….……………….……………………………….……….……………………………….……….
…………………………………………………………………….
Question 1. What is meant by reactivity series of metals?
…………………………………………………………………………………….
Question 2. Arrange the following metals according to the reactivity series, in descending order
Aurum, silver, carbon potassium, magnesium, hydrogen , sodium, mercury, aluminum, zinc, copper, lead, iron, tin
Question 3
Which substances react with each other? If the substances react, write chemical equations
a) Na2O + Mg ……………………………………………………….
b) Mg + CuO ……………………………………………………….
c) C + PbO …………………………………………………………..
d) H2 + ZnO …………………………………………………………
e) Fe + Ag2O …………………………………………………………
8
f) CaO + Zn ……………………………………………………………
Question 4
Table of extraction of metals
Reactivity increases
K These metals have very strong attraction towards oxygen, therefore the oxides cannot be reduced by Carbon
Extraction of metals must be done by electrolysis of molten compounds
NaCaMgAl
CZn These metals have weak attraction towards oxygen compared to
carbon, so the ores can be extracted easily by carbonHFeSnPbCu Weak attraction towards oxygen, therefore heating the oxides in air
can reduce the metals easilyHgAg Very weak attraction towards oxygen. Exist as free metalsAu
How are these metals extracted from their ores? Use the table above to help you
a) Zinc from zinc sulphide …………………………………..
b) Iron from iron(III) oxide …………………………………..
c) Copper from copper(II) sulphide …………………………..
d) Aluminum from aluminum oxide ……………………..
e) Tin from tin(IV) oxide …………………………………
f) Gold and silver …………………………………………..
Question 5Zinc is below magnesium in the reactivity series. Can zinc be extracted from zinc oxide using magnesium? Explain
………………………………………………………………………………………Question 6Why is carbon the preferred element used to reduce metals and not hydrogen or other metals?
9
…………………………………………………………………………………………………..
Question 1
Complete the table below for differences between electrolytic cell and chemical cell
Electrolytic cell Chemical cell/voltaic cellDraw Diagram Example for
Electrolysis of copper(II) sulphate using carbon electrode
……………………………….
Example for Voltaic cell using copper and zinc as electrodes, and copper(II) sulphate and zinc sulphate as electrolytes
……………………………………..
Presence of voltmeter or ammeter? And why?
……………………………………… ……………………………………..
Change of energy
Positive electrode Negative electrode
Positive electrode Negative electrode
Type of electrode Electrode that is joined to the …….. part of the battery
Electrode that is joined to the …….. part of the battery
Less electronegative
metal becomes + electrode
More electronegative
metal becomes - electrode
Oxidation occur at ( release e-)and write half equationReduction occur at (accept e-)and write half equation Cathode(area where electrons are accepted)Anode(area where electrons are released)
10
Complete module 3………….Alhamdulillah!!
11