# 18.2 Occurrence and preparation of the representative metals  (Page 3/7)

 Page 3 / 7

The production of magnesium, zinc, and tin provide additional examples of chemical reduction.

## The preparation of magnesium

The Pidgeon process    involves the reaction of magnesium oxide with elemental silicon at high temperatures to form pure magnesium:

$\text{Si}\left(s\right)+\text{2MgO}\left(s\right)\phantom{\rule{0.2em}{0ex}}\stackrel{\phantom{\rule{0.4em}{0ex}}\text{Δ}\phantom{\rule{0.4em}{0ex}}}{\to }\phantom{\rule{0.2em}{0ex}}{\text{SiO}}_{2}\left(s\right)+\text{2Mg}\left(g\right)$

Although this reaction is unfavorable in terms of thermodynamics, the removal of the magnesium vapor produced takes advantage of Le Châtelier’s principle to continue the forward progress of the reaction. Over 75% of the world’s production of magnesium, primarily in China, comes from this process.

## The preparation of zinc

Zinc ores usually contain zinc sulfide, zinc oxide, or zinc carbonate. After separation of these compounds from the ores, heating in air converts the ore to zinc oxide by one of the following reactions:

$\text{2ZnS}\left(s\right)+{\text{3O}}_{2}\left(g\right)\phantom{\rule{0.2em}{0ex}}\stackrel{\phantom{\rule{0.4em}{0ex}}\text{Δ}\phantom{\rule{0.4em}{0ex}}}{\to }\phantom{\rule{0.2em}{0ex}}\text{2ZnO}\left(s\right)+{\text{2SO}}_{2}\left(g\right)$
${\text{ZnCO}}_{3}\left(s\right)\phantom{\rule{0.2em}{0ex}}\stackrel{\phantom{\rule{0.4em}{0ex}}\text{Δ}\phantom{\rule{0.4em}{0ex}}}{\to }\phantom{\rule{0.2em}{0ex}}\text{ZnO}\left(s\right)+{\text{CO}}_{2}\left(g\right)$

Carbon, in the form of coal, reduces the zinc oxide to form zinc vapor:

$\text{ZnO}\left(s\right)+\text{C}\left(s\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{Zn}\left(g\right)+\text{CO}\left(g\right)$

The zinc can be distilled (boiling point 907 °C) and condensed. This zinc contains impurities of cadmium (767 °C), iron (2862 °C), lead (1750 °C), and arsenic (613 °C). Careful redistillation produces pure zinc. Arsenic and cadmium are distilled from the zinc because they have lower boiling points. At higher temperatures, the zinc is distilled from the other impurities, mainly lead and iron.

## The preparation of tin

The ready reduction of tin(IV) oxide by the hot coals of a campfire accounts for the knowledge of tin in the ancient world. In the modern process, the roasting of tin ores containing SnO 2 removes contaminants such as arsenic and sulfur as volatile oxides. Treatment of the remaining material with hydrochloric acid removes the oxides of other metals. Heating the purified ore with carbon at temperature above 1000 °C produces tin:

${\text{SnO}}_{2}\left(s\right)+\text{2C}\left(s\right)\phantom{\rule{0.2em}{0ex}}\stackrel{\phantom{\rule{0.4em}{0ex}}\text{Δ}\phantom{\rule{0.4em}{0ex}}}{\to }\phantom{\rule{0.2em}{0ex}}\text{Sn}\left(s\right)+\text{2CO}\left(g\right)$

The molten tin collects at the bottom of the furnace and is drawn off and cast into blocks.

## Key concepts and summary

Because of their chemical reactivity, it is necessary to produce the representative metals in their pure forms by reduction from naturally occurring compounds. Electrolysis is important in the production of sodium, potassium, and aluminum. Chemical reduction is the primary method for the isolation of magnesium, zinc, and tin. Similar procedures are important for the other representative metals.

## Chemistry end of chapter exercises

Write an equation for the reduction of cesium chloride by elemental calcium at high temperature.

$\text{2CsCl}\left(l\right)+\text{Ca}\left(g\right)\phantom{\rule{0.2em}{0ex}}\stackrel{\phantom{\rule{0.7em}{0ex}}\begin{array}{l}\text{countercurrent}\\ \text{fractionating}\\ \text{tower}\end{array}}{\to }\phantom{\rule{0.2em}{0ex}}\text{2Cs}\left(g\right)+{\text{CaCl}}_{2}\left(l\right)$

Why is it necessary to keep the chlorine and sodium, resulting from the electrolysis of sodium chloride, separate during the production of sodium metal?

Give balanced equations for the overall reaction in the electrolysis of molten lithium chloride and for the reactions occurring at the electrodes. You may wish to review the chapter on electrochemistry for relevant examples.

Cathode (reduction): ${\text{2Li}}^{+}+{\text{2e}}^{-}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{2Li}\left(l\right)\text{;}$ Anode (oxidation): ${\text{2Cl}}^{-}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{Cl}}_{2}\left(g\right)+{\text{2e}}^{\text{−}};$ Overall reaction: ${\text{2Li}}^{+}+{\text{2Cl}}^{-}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{2Li}\left(l\right)+{\text{Cl}}_{2}\left(g\right)$

The electrolysis of molten sodium chloride or of aqueous sodium chloride produces chlorine.

Calculate the mass of chlorine produced from 3.00 kg sodium chloride in each case. You may wish to review the chapter on electrochemistry for relevant examples.

What mass, in grams, of hydrogen gas forms during the complete reaction of 10.01 g of calcium with water?

0.5035 g H 2

How many grams of oxygen gas are necessary to react completely with 3.01 $×$ 10 21 atoms of magnesium to yield magnesium oxide?

Magnesium is an active metal; it burns in the form of powder, ribbons, and filaments to provide flashes of brilliant light. Why is it possible to use magnesium in construction?

Despite its reactivity, magnesium can be used in construction even when the magnesium is going to come in contact with a flame because a protective oxide coating is formed, preventing gross oxidation. Only if the metal is finely subdivided or present in a thin sheet will a high-intensity flame cause its rapid burning.

Why is it possible for an active metal like aluminum to be useful as a structural metal?

Describe the production of metallic aluminum by electrolytic reduction.

Extract from ore: $\text{AlO}\left(\text{OH}\right)\left(s\right)+\text{NaOH}\left(aq\right)+{\text{H}}_{2}\text{O}\left(l\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{Na}\left[\text{Al}{\left(\text{OH}\right)}_{4}\right]\left(aq\right)$
Recover: $\text{2Na}\left[\text{Al}{\left(\text{OH}\right)}_{4}\right]\left(s\right)+{\text{H}}_{2}{\text{SO}}_{4}\left(aq\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{2Al}{\left(\text{OH}\right)}_{3}\left(s\right)+{\text{Na}}_{2}{\text{SO}}_{4}\left(aq\right)+{\text{2H}}_{2}\text{O}\left(l\right)$
Sinter: $\text{2Al}{\left(\text{OH}\right)}_{3}\left(s\right)\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}{\text{Al}}_{2}{\text{O}}_{3}\left(s\right)+{\text{3H}}_{2}\text{O}\left(g\right)$
Dissolve in Na 3 AlF 6 ( l ) and electrolyze: ${\text{Al}}^{3+}+{\text{3e}}^{-}\phantom{\rule{0.2em}{0ex}}⟶\phantom{\rule{0.2em}{0ex}}\text{Al}\left(s\right)$

What is the common ore of tin and how is tin separated from it?

A chemist dissolves a 1.497-g sample of a type of metal (an alloy of Sn, Pb, Sb, and Cu) in nitric acid, and metastannic acid, H 2 SnO 3 , is precipitated. She heats the precipitate to drive off the water, which leaves 0.4909 g of tin(IV) oxide. What was the percentage of tin in the original sample?

25.83%

Consider the production of 100 kg of sodium metal using a current of 50,000 A, assuming a 100% yield.

(a) How long will it take to produce the 100 kg of sodium metal?

(b) What volume of chlorine at 25 °C and 1.00 atm forms?

What mass of magnesium forms when 100,000 A is passed through a MgCl 2 melt for 1.00 h if the yield of magnesium is 85% of the theoretical yield?

39 kg

#### Questions & Answers

what are oxidation numbers
Idowu Reply
pls what is electrolysis
Idowu Reply
Electrolysis is the process by which ionic substances are decomposed (broken down) into simpler substances when an electric current is passed through them. ... Electricity is the flow of electrons or ions. For electrolysis to work, the compound must contain ions.
AZEEZ
thanks
Idowu
what is the basicity of an atom
Eze Reply
basicity is the number of replaceable Hydrogen atoms in a Molecule. in H2SO4, the basicity is 2. in Hcl, the basicity is 1
Inemesit
how to solve oxidation number
Mr Reply
mention some examples of ester
Chinenye Reply
do you mean ether?
Megan
what do converging lines on a mass Spectra represent
Rozzi Reply
would I do to help me know this topic ?
Bulus
oi
Amargo
what the physic?
Bassidi Reply
who is albert heistein?
Bassidi
similarities between elements in the same group and period
legend Reply
what is the ratio of hydrogen to oxulygen in carbohydrates
Nadeen Reply
bunubyyvyhinuvgtvbjnjnygtcrc
Nadeen
yvcrzezalakhhehuzhbshsunakakoaak
Nadeen
what is poh and ph
Amarachi Reply
please what is the chemical configuration of sodium
Sharon
2.8.1
david
1s²2s²2p⁶3s¹
Haile
2, 6, 2, 1
Salman
1s2, 2s2, 2px2, 2py2, 2pz2, 3s1
Justice
1s2,2s2,2py2,2
Maryify
1s2,2s2,2p6,
Francis
1s2,2s2,2px2,2py2,2pz2,3s1
Nnyila
what is criteria purity
Austin Reply
cathode is a negative ion why is it that u said is negative
Michael Reply
cathode is a negative electrode while cation is a positive ion. cation move towards cathode plate.
king
CH3COOH +NaOH ,complete the equation
david Reply
compare and contrast the electrical conductivity of HCl and CH3cooH
Sa Reply
The must be in dissolved in water (aqueous). Electrical conductivity is measured in Siemens (s). HCl (aq) has higher conductivity, as it fully ionises (small portion of CH3COOH (aq) ionises) when dissolved in water. Thus, more free ions to carry charge.
Abdelkarim
HCl being an strong acid will fully ionize in water thus producing more mobile ions for electrical conduction than the carboxylic acid
Valentine
differiante between a weak and a strong acid
david
how can I tell when an acid is weak or Strong
Amarachi
an aqueous solution of copper sulphate was electrolysed between graphite electrodes. state what was observed at the cathode
Bakanya Reply
write the equation for the reaction that took place at the anode
Bakanya
what is enthalpy of combustion
Bakanya
Enthalpy change of combustion: It is the enthalpy change when 1 mole of substance is combusted with excess oxygen under standard conditions. Elements are in their standard states. Conditions: pressure = 1 atm Temperature =25°C
Abdelkarim
Observation at Cathode: Cu metal deposit (pink/red solid).
Abdelkarim
Equation at Anode: (SO4)^2- + 4H^+ + 2e^- __> SO2 + 2H2O
Abdelkarim
Equation : CuSO4 -> Cu^2+ + SO4^2- equation at katode: 2Cu^2+ + 4e -> 2Cu equation at anode: 2H2O -> 4H+ + O2 +4e at the anode which reacts is water because SO4 ^ 2- cannot be electrolyzed in the anode
Niken

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