CH 8 Chemical Reactions and Equations

1
CH 8 Chemical Reactions and Equations

• SECTIONS 1 AND 2

2
Chemical Change

• One or more substances changes into one or more
  new substances.
• Evidence
• Changes in energy

3
Chemical Change

• Evidence
• Formation of new substances
• ________ (bubbles in solution, pressure change
  in a closed system)
• _________(a cloudy solid that settles out of
  solution)
• _________ change
• _________change

4
Collision Theory of Reactions

• Chemicals must come into contact (________)
• The contact must be in the correct orientation
  (___________________)
• There must be enough energy for the reactants to
  get started (________________)

5
Chemical equations

• Equations are used to describe chemical processes
• Equations show physical states of matter (s, l,
  g) and some reaction conditions.

6

• In words
• Solid magnesium and oxygen gas when heated, react
  to form solid Magnesium Oxide.

7
Symbols used in chemical equations

• Pt
• ?
• ( ) Solid
• ( ) Liquid
• ( ) Gas
• ( ) aqueous

• ?
• ?

8
2 arrows means reversible reaction

• Reversible reaction goes both waysThe
  products form, and can un-form
• Most reactions that happen in your cells are
  reversible reactions

9
Elemental forms

• Exceptions
• Diatomic Gases
• Non Gases

• Most elements come naturally in ones
• Ex.
• Sodium Na
• Magnesium Mg
• Iron Fe

10
Write unbalanced equations for the following

• Aqueous Sodium Hydroxide and hydrogen chloride
  gas
• React to form
• Water and aqueous Sodium Chloride
• Unbalanced means dont put any coefficients

11
Write out this reaction using symbols

• Solid Lithium reacts with water, forming lithium
  hydroxide solution and Hydrogen gas.

12
In a reaction

• Mass is neither created nor destroyed.
• Your bag was a closed system. No atoms were
  added or removed. They were rearranged.
• Law of Conservation of Mass

13
Rules for Balancing Equations

1. Count the number and type of each element on the
   reactants side. Do the same for the products
   side.
2. Check to see if there are any elements not in
   balance.
3. Use coefficients to balance any elements that are
   not equal.
4. Coefficients affect all parts of the molecule
   that follows.

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__ N2 __ H2 ? __ NH3

• Coefficients
• multiply through the whole molecule.
• Must be a whole number
• Are placed in front of molecules not between.

15
Write balanced equations for the following

• Sodium Hydroxide and hydrogen chloride
• React to form
• Water and Sodium Chloride

16
Balance this reaction

• Lithium reacts with water
• Forming lithium hydroxide and Hydrogen gas

17
Write the equation and balance it using
coefficients

• Lithium reacts with oxygen
• To produce Lithium oxide
• Silver Nitride is produced when silver metal
  reacts with nitrogen from the atmosphere.

18
Warm Up

• How many Oxygen atoms are there in each of the
  following compounds?
• NO2 _______
• 2 NO2 _____
• 2 Mg(NO3)2 _______

19
Balance the following

• Li H2O ? LiOH H2
• C6H12O6 O2 ? H20 CO2

20
Warm Ups

• What is the mass of 1.204E24 molecules of Oxygen
  gas?
• How many formula units are there in 50.0g of
  Magnesium Chloride?
• How many atoms are there in the same amount of
  MgCl2?