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Chemical Equations & Reactions. Physical Properties. color melting point boiling point electrical conductivity specific heat density state (solid, liquid, or gas). Physical Change. Changes in physical properties melting boiling condensation

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physical properties
Physical Properties
  • color
  • melting point
  • boiling point
  • electrical conductivity
  • specific heat
  • density
  • state (solid, liquid, or gas)
physical change
Physical Change

Changes in physical properties

  • melting
  • boiling
  • condensation

No change occurs in the identity of the substance

Example:

Ice , rain, and steam are all water

chemical change
Chemical Change
  • Atoms in the reactants are rearranged to form one or more different substances
  • Old bonds are broken; new bonds form

Examples:

Fe and O2 form rust (Fe2O3)

Ag and S form tarnish (Ag2S)

describing a chemical reaction
Describing a Chemical Reaction

Indications of a Chemical Reaction

  • Evolution of heat, light, and/or sound
  • Production of a gas
  • Formation of a precipitate
  • Color change
learning check e1
Learning Check E1

Classify each of the following as a

1) physical change or 2) chemical change

A. ____ a burning candle

B. ____ melting ice

C. ____ toasting a marshmallow

D. ____ cutting a pizza

E. ____ polishing silver

solution e1
Solution E1

Classify each of the following as a

1) physical change or 2) chemical change

A. __2__ a burning candle

B. __1_ melting ice

C. __2__ toasting a marshmallow

D. __1__ cutting a pizza

E. __2__ polishing silver

meaning of chemical formula
Meaning of Chemical Formula

Chemical

Symbol Meaning Composition

H2O One molecule

of water:

Two H atoms and one O atom

2 H2O Two molecules

of water:

Four H atoms and two O atoms

H2O2 One molecule

of hydrogen

peroxide:

Two H atoms and two O atoms

coefficients
Coefficients
  • A formula may begin with a number.
  • If there is no number, then “1” is understood to be in front of the formula.
    • This number is called the coefficient.
    • The coefficient represents the number of molecules of that compound or atom needed in the reaction.
    • For example:
      • 2H2SO4 – 2 molecules of Sulfuric Acid
coefficients1
Coefficients
  • 2H2SO4 – 2 molecules of Sulfuric Acid
    • A coefficient is distributed to ALL elements in a compound
      • 2 – H2 (for a total of 4 H atoms)
      • 2 – S (for a total of 2 S atoms)
      • 2 – O4 (for a total of 8 O atoms)
chemical reaction
Chemical Reaction

A process in which at least one new substance is produced as a result of chemical change.

a chemical reaction
A Chemical Reaction

Reactants Products

learning check e2
Learning Check E2

A. How does an equation indicate a change in

the identity of the reacting substances?

B. How did the yellow and green reactants

combine?

C. Did all the reactants form product? Why or

why not?

learning check e21
Learning Check E2

A. How does an equation indicate a change in

the identity of the reacting substances?

The formulas of the reactants are different

than the formulas of the products.

B. How did the yellow and green reactants

combine? 1 yellow combined with 1 green.

C. Did all the reactants form product? Why or

why not? No. There were more yellow

reactants than green.

chemical equations
Chemical Equations
  • Reactants– the substances that exist before a chemical change (or reaction) takes place.
  • Products– the new substance(s) that are formed during the chemical changes.
  • CHEMICAL EQUATION indicates the reactants and products of a reaction.

REACTANTS  PRODUCTS

writing a chemical equation
Writing a Chemical Equation

Chemical symbols give a “before-and-after” picture of a chemical reaction

Reactants Products

MgO + C CO + Mg

magnesium oxide to form carbon monoxide

reacts with carbon and magnesium

reading a chemical equation
Reading A Chemical Equation

4 NH3 + 5 O2 4 NO + 6 H2O

Four molecules of NH3 react with five molecules O2to produce four molecules NO and six molecules of H2O

or

Four moles NH3 react with 5 moles O2toproduce four moles NO and six moles H2O

reading chemical equations
Reading Chemical Equations
  • Each side of an equation represents a combination of chemicals.
  • The combination is written as a set of chemical formulas, separated by + symbols.

CH4 + 2 O2 → CO2 + 2 H2O

Coefficient

balancing chemical equations
Balancing Chemical Equations

Balanced Equation – one in which the number of atoms of each element as a reactant is equal to the number of atoms of that element as a product

What is the relationship between conservation of mass and

the fact that a balanced equation will always have the same

number of atoms of each element on both sides of an equation?

Determine whether the following equation is balanced.

2 Na + H2O  2 NaOH + H2

2 Na + 2 H2O  2 NaOH + H2

unbalanced and balanced equations
Unbalanced and Balanced Equations

H

Cl

Cl

H

H

Cl

H

Cl

Cl

Cl

H

Cl

H

H

H2 + Cl2 2 HCl (balanced)

H2 + Cl2 HCl (unbalanced)

reactants products

reactants products

H

H

2 1

2 2

Cl

Cl

2 1

2 2

balancing chemical equations1
Balancing Chemical Equations
  • Write a word equation for the reaction.
  • Write the correct formulas for all reactants and products.
  • Determine the coefficients that make the equation balance.
a balanced chemical equation
A Balanced Chemical Equation

Same numbers of each type of atom on each side of the equation

Al + S Al2S3 Not Balanced

2Al + 3S Al2S3Balanced

balance equations with coefficients
Balance Equations with Coefficients

Coefficients in front of formulas balance each type of atom

4NH3 + 5O24NO + 6H2O

4 N = 4 N

12 H = 12 H

10 O = 10 O

balance equations with coefficients1
Balance Equations with Coefficients

Coefficients in front of formulas balance each type of atom

4NH3 + 5O24NO + 6H2O

4 N = 4 N

12 H = 12 H

10 O = 10 O

steps in balancing an equation
Steps in Balancing An Equation

Fe3O4 + H2 Fe +H2O

Fe:Fe3O4 + H23 Fe +H2O

O:Fe3O4 + H2 3 Fe +4H2O

H: Fe3O4 + 4 H2 3 Fe +4H2O

learning check e4
Learning Check E4

Fe3O4 + 4 H2 3 Fe +4H2O

A. Number of H atoms in 4 H2O

1) 2 2) 4 3) 8

B. Number of O atoms in 4 H2O

1) 2 2) 4 3) 8

C. Number of Fe atoms in Fe3O4

1) 1 2) 3 3) 4

solution e4
Solution E4

Fe3O4 + 4 H2 3 Fe +4H2O

A. Number of H atoms in 4 H2O

3) 8

B. Number of O atoms in 4 H2O

2) 4

C. Number of Fe atoms in Fe3O4

2) 3

learning check e5
Learning Check E5

Balance each equation. The coefficients for each equation are read from left to right

A. Mg + N2 Mg3N2

1) 1, 3, 2 2) 3, 1, 2 3) 3, 1, 1

B. Al + Cl2 AlCl3

1) 3, 3, 2 2) 1, 3, 1 3) 2, 3, 2

learning check e51
Learning Check E5

C. Fe2O3 + C Fe + CO2

1) 2, 3, 2,3 2) 2, 3, 4, 3 3) 1, 1, 2, 3

D. Al + FeO Fe + Al2O3

1) 2, 3, 3, 1 2) 2, 1, 1, 1 3) 3, 3, 3, 1

E. Al + H2SO4 Al2(SO4)3 + H2

1) 3, 2, 1, 22) 2, 3, 1, 3 3) 2, 3, 2, 3

solution e5
Solution E5

A. 3 Mg + N2 Mg3N2

B. 2 Al + 3 Cl2 2 AlCl3

C. 2 Fe2O3 + 3 C 4 Fe + 3 CO2

D. 2 Al + 3 FeO 3 Fe + Al2O3

E. 2 Al + 3 H2SO4 Al2(SO4)3 + 3 H2

ch 4 2 o 2 co 2 2 h 2 o
CH4 + 2 O2 CO2 + 2 H2O

Reactants Products

1 C atom 1 C atom

4 H atoms 4 H atoms

4 O atoms 4 O atoms

slide33

Write a balanced equation for the reaction between chlorine

and sodium bromide to produce bromine and sodium chloride.

1) Write a word equation for the reaction.

chlorine + sodium bromide  bromine + sodium chloride

2) Write the correct formulas for all reactants and products.

Cl2 + NaBr  Br2 + NaCl

3) Determine the coefficients that make the equation balance.

Cl2 + 2 NaBr  Br2 + 2 NaCl

slide34

Write the balanced equation for the reaction between aluminum sulfate and calcium chloride to form a white precipitate of calcium sulfate.

1) Write a word equation for the reaction.

aluminum sulfate + calcium chloride  calcium sulfate + aluminum chloride

2) Write the correct formulas for all reactants and products.

Al2(SO4)3 + CaCl2 CaSO4 + AlCl3

3) Determine the coefficients that make the equation balance.

Al2(SO4)3 + 3 CaCl2 3 CaSO4 + 2 AlCl3

showing phases in chemical equations
Showing Phases in Chemical Equations
  • Solid Phase – the substance is relatively rigid and has a definite volume and shape. NaCl(s)
  • Liquid Phase – the substance has a definite volume, but is able to change shape by flowing. H2O(l)
  • Gaseous Phase – the substance has no definite volume or shape, and it shows little response to gravity. Cl2(g)

H2O(s) H2O(l) H2O(g)

matter is conserved
Matter Is Conserved

H2 + Cl2 2 HCl

+ +

Total atoms = Total atoms

2 H, 2 Cl 2H, 2 Cl

Total Mass = Total Mass

2(1.0) + 2(35.5) 2(36.5)

73.0 g = 73.0 g

law of conservation of mass
Law of Conservation of Mass

In any ordinary chemical reaction, matter is not created nor destroyed

synthesis reaction
Synthesis Reaction

Direct combination reaction (Synthesis)

2 Na + Cl2 2 NaCl

Na

Cl

Na+

Cl -

Cl

Cl -

Na+

Na

General form: A + B  AB

element orelement orcompound

compoundcompound

you try
You try…
  • Al + Br2→ AlBr3

Is it balanced?

  • 2 Al + 3 Br2→ 2 AlBr3
  • H2 + SO3 → H2SO4

Balance it…

  • 3H2 + 4SO3 → 3H2SO4
decomposition reaction
Decomposition Reaction

Decomposition reaction

2 H2O

+

2 H2

O2

H

O

H

H

O

H

+

O

H

O

H

H

H

General form: AB

A

+

B

compound

two or more elements

or compounds

single and double replacement reactions
Single and Double Replacement Reactions

Single-replacement reaction

Mg + CuSO4 MgSO4 + Cu

General form:

A + BC  AC + B

Double-replacement reaction

CaCO3 + 2 HCl  CaCl2 + H2CO3

General form:

AB + CD  AD + CB

activity series
Activity Series

Element Reactivity

Li

Rb

K

Ba

Ca

Na

Mg

Al

Mn

Zn

Cr

Fe

Ni

Sn

Pb

H2

Cu

Hg

Ag

Pt

Au

Ca

Foiled again –

Aluminum loses to Calcium

Halogen Reactivity

F2

Cl2

Br2

I2

how do you know if a double displacement reaction occurred
How do you know if a Double Displacement Reaction Occurred?
  • A new gas
  • Formation of a precipitate
  • Neutralization of an acid and base.
formation of a solid agcl
Formation of a solid: AgCl

AgNO3(aq) + KCl(aq)  KNO3 (aq) + AgCl(s)