chapter 3d chemical equation

8/8/2019 Chapter 3d Chemical Equation

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Chemical EquationChemical EquationChemical EquationChemical Equation


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Learning objective : Interpret chemical equations

Learning outcomes : Identify the reactants & products of

a chemical equation.

Write & balance chemical equations.


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Chemical Equation Is a precise description of a

chemical reaction.


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2H2(g) + O2(g) 2 H2O(l)

Reactans Product

( starting substances ) ( new substances )


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(a) C + O2 CO2

(b) CuO + Mg MgO + Cu


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Magnesium reacts with dilutehydrochloric acid, HCl to producemagnesium chloride, MgCl2 and

hydrogen gas, H2.

Reactants ?

Products ?


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2 H2(g) + O2(g) 2 H2O(l)

Physical states


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Solid (s) Liquid (l)

Aqueous solution (aq)

Gas (g)


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Mg (_) + O2(_) MgO (_)


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When solid zinc carbonate is heated, itdecomposes into zinc oxide powder andcarbon dioxide gas.

Reactants ?

Products ?

Physical states of reactants & products ?


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2 H2(g) + O2(g) 2 H2O(l)

Number of mole


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Kinetic Theory of Matter :Matter can neither be created nordestroyed.

number of atoms before & aftera chemical reaction must be thesame.


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Mg + O2 MgO


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(a) K + Br2 KBr

(b) Al + CuO Al2O3 + Cu(c) Na + H2O NaOH + H2(d) C2H4 + O2 CO2 + H2O

(e) HCl + Mg MgCl2 + H2(f) H2SO4 + NaOH Na2SO4 + H2O

(g) Pb(NO3

)2 + KCl PbCl2 + KNO3(h) CaCO3 + HCl CaCl2 + CO2 + H2O


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Titbits :

1. Balance the equation ( adjusting coefficient )

Never change the subscript numbers in theformulae.

2. : release of gas ;

3. (above the arrow) : heating is necessary.


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Construct a balanced equation :Iron react with copper (II) chloride toproduce iron (III) chloride solution &copper.


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Construct a balanced equation :Aluminium reacts with solid copper(II) oxide to produce solid aluminium

oxide & copper.


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Homework :

Text book :

Activity 3.12( Page 50 )


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Rather than a lot of words,say a few words ;

rather than a few words,say good words.

~ Still Thoughts


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Solving problem usingchemical equation

A balanced equation can be used tocalculate the number of moles, mass orvolume of a reactant / product.


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Example 1

2K(s) + Br2(g)

2KBr(s)How many moles of potassium areneeded to react with 0.5 mole of

bromine gas ?

2 mol Kreact with 1 mol Br2

? mol 0.5 molAns : 1 mol K


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Example 2

Ethene gas burns in excessive oxygenas follows :

C2H4(g) + 3O2(g) 2CO2(g) + 2H2O(l)

Find the volume of CO2 released atSTP if 42 g of ethene gas is burntcompletely.

[ Relative atomic mass : H, 1 ; C, 12 ;Molar volume : 22.4 dm3 mol-1 at STP ]


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Example 3

Zn(s) + 2HNO3

(aq) Zn(NO3

)2

(aq) + H2

(g)

What is the mass of zinc needed toproduce 2.4 dm3 of hydrogen gas atroom condition ?

[ Relative atomic mass : Zn, 65 ; Molarvolume : 24 dm3 mol-1 at STP ]


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Example 4

Aluminium reacts with copper (II)oxide to produce aluminium oxide &copper. If 2.0 g of excess aluminium isreacted with 0.06 mole of copper (II)

oxide, find the mass of aluminium leftafter the reaction.

[ Relative atomic mass : Al, 27 ]

chapter 3d chemical equation

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