UNIT VIChemical Reactions

VI.1 INTRODUCTION TO CHEMICAL EQUATIONS

A chemical reaction (or chemical change) involves the formation of a __________________________.

reactants (starting materials) form a chemically different product.

Changes that accompany chemical reactions include:

____________________________________ ____________________________________ ____________________________________

VI.1 INTRODUCTION TO CHEMICAL EQUATIONS

A chemical reaction equation is ____________________________________________________________________________________________________________________________________________________________________________________

VI.1 INTRODUCTION TO CHEMICAL EQUATIONS

Ex: 2H2 + O2 → 2H2 O 

The word equation is: “Hydrogen gas reacts with oxygen gas to form water”.

Coefficient is __________________________________________________________________________________________

  refers to the

_____________________________________________

VI.2 THE CONSERVATION LAWS

In a CLOSED system, the total mass of products is EQUAL to the total mass of reactants involved in a chemical reaction.

mass (reactants) = mass (products)

A system (part of the universe being studied) is CLOSED when nothing can enter or leave the system.

VI.2 THE CONSERVATION LAWS

Law of Conservation of Mass: states that the total ___________ of ALL REACTANTS before a chemical reaction equals the total __________ of ALL PRODUCTS after the chemical reaction.

  For this to be true: the total number of ___________ must be

constant bonds between atoms are broken and new

bonds form...but same atoms are there

VI.2 THE CONSERVATION LAWS

More laws of conservation on page 106 in Hebden!

Law of conservation of atoms Law of conservation of electrical charge Law of conservation of energy

Questions: p. 106-107: #1-6

VI.3 BALANCING CHEMICAL EQUATIONS

To write and balance an equation:

write what you believe is happening (include the formulae of reactants and products)

balance each side so the two sides are EQUAL balance by placing a ________________ in

front of a formulaNEVER change ________________ on atoms

VI.3 BALANCING CHEMICAL EQUATIONS

Steps to balancing an equation (guidelines) Start with atoms which occur once on each

side Then balance the metals (or any other non-

hydrogen, non-oxygen atoms) Balance polyatomic ions as a whole Leave H and O until very last

*if a fraction (ex: 3/2) occurs during balancing, multiply the equation by the whole number (ex:2) to eliminate the fraction.

VI.3 BALANCING CHEMICAL EQUATIONS

VI.3 BALANCING CHEMICAL EQUATIONS

VI.3 BALANCING CHEMICAL EQUATIONS

Example #1:___ Na + ___ H2O → ___ NaOH + ___ H2

VI.3 BALANCING CHEMICAL EQUATIONS

Example #2: __(NH4)2SO4 + __NaOH → __NH3 + __H2O +

__Na2SO4

VI.3 BALANCING CHEMICAL EQUATIONS

Example #3: ___ AgNO3 + ___ CuCl2 → ___ AgCl + ___Cu(NO3)2

VI.3 BALANCING CHEMICAL EQUATIONS

Example #4: ___ CuSO4 + ____ Fe → ____Cu + ___Fe2(SO4)3

http://phet.colorado.edu/en/simulation/balancing-chemical-equations

Questions: p. 110-111 #7-52 (every third question) – PRACTICE

VI.4 WRITING PHASES IN REACTION EQUATIONS & USING CHEMICAL WORD EQUATIONS

Phases are also shown in chemical reaction equations

s = solid phasel = liquid phaseg = gaseous phaseaq = aqueous phase (dissolved in water)

ex: 2H2(g) + O2(g) → 2H2 O(g)

The word SOLID can also be stated as crystal, powder, and precipitate (precipitate is formed when two liquid or aqueous solutions react)

VI.4 WRITING PHASES IN REACTION EQUATIONS & USING CHEMICAL WORD EQUATIONS

Diatomic molecules - seven of the elements form diatomic molecules:

N, O, F, Cl, Br, I and H (p. 113) * on the periodic table, they form the shape

of a 7 plus one (H)

VI.4 WRITING PHASES IN REACTION EQUATIONS & USING CHEMICAL WORD EQUATIONS

Writing chemical equations from the word equation:

Ex #1: Aqueous bromine is replaced by chlorine in potassium bromide to form potassium chloride.

VI.4 WRITING PHASES IN REACTION EQUATIONS & USING CHEMICAL WORD EQUATIONS

Ex #2: Solid aluminum oxide and aqueous sulphuric acid produce water and aqueous aluminum sulphate

Questions: p.113 # 57, 58-64 (even)