Chemical Reactions

- The essence of chemical reactions is the making of a new substance, through a chemical process. - Mass is conserved in a chemical reaction. The mass of the reactants, the amounts of the reactants, must equal the mass or amounts of products. (______) - This means that ______are formed by the rearranging of ______to make a new substance

- All chemical reactions are based upon energy. If there is enough energy, the reaction goes; if not, the reaction does not occur.

o 95% of all reactions will go to completion (REACTANTS to PRODUCTS) o These reactions are considered SPONTANEOUS REACTIONS

Where does the energy come from?

- Internal

- External

What state will cause the greatest reaction?

- When something is unstable it will react to create a stable substance o Disorder Order o This change of disorder to order arrangement is called Entropy

State of a Reaction

Solid Liquid Gas

Ordered Disorder

Least Reactive Most Reactive

- Due to the fact gases are difficult to control, we prefer to use liquids - Since you cannot really “liquefy” solids, without a lot of energy, we dissolve them in water to form a more reactive solution, as the particles are spread out, and the reaction will occur faster.

The Mechanism for Chemical Change

Read p. 109 – 110. Take notes on Kinetic Molecular Theory, how the Kinetic Molecular Theory relates to the Collision (Reaction) Theory and chemical reactions occurring. Chemical Equations

The chemical reaction is the recipe. The chemical equation shows the ingredients; it shows the formulas of the reactants and the resulting products.

Example

Chemical Reaction

Chemical Equation

REACTANTS PRODUCTS

(s) – (aq) – (l) – (g) –

Hydrogen gas reacts with oxygen gas to produce water.

Why do we need to balance the equation? Rules of Balancing Equations

Examples

Na(s) + Cl2(g) NaCl(s)

Iodine crystals react with hydrogen gas to produce hydrogen iodide.

Mg(s) + HCl(aq) MgCl2(aq) + H2(g)

Lead (II) nitrate reacts with potassium iodide to produce lead (II) iodide and potassium nitrate. Balancing Chemical Equations

Balance the following equations. For the chemical reactions, write out the formulas and the chemical equation, and balance.

1. BaCl2(aq) + CuSO4(aq) CuCl2(aq) + BaSO4(s)

2. Al(s) + HCl(aq) AlCl3(aq) + H2(g)

3. Iron (III) chloride reacts with barium carbonate to produce iron (III) carbonate and barium chloride.

4. CO2(g) + H2O(l) H2CO3(aq)

5. Na(s) + O2(g) Na2O(s)

6. Potassium chlorate breaks down to produce potassium chloride and oxygen gas.

7. Copper metal reacts with a solution of silver (I) nitrate to produce silver metal and copper (II) nitrate.

8. Na(s) + H2O(l) NaOH(aq) + H2(g) Types of Chemical Reactions

There are 5 types of reactions:

1. Synthesis 2. Decomposition 3. Single Displacement 4. Double Displacement 5. Combustion

Read the pages 114 – 139. Define each of the above reactions, give an example for each.

Determining whether a chemical reaction takes place

There are several diagnostic tests that can be done.

Using the lab results below, and some internet resources:

1. How can we determine whether a chemical reaction has taken place? 2. What are the basic diagnostic tests used? Chemical Reactions

For each of the reactions, you will need to:  record the physical properties of the reactants  record your observations, before during and after the reaction  state what type of reaction  how you know a reaction took place  balance the equations for each experiment

1. Reaction of hydrogen peroxide and yeast

***Yeast is used as a catalyst to speed up the reaction

H2O2(aq) H2O(l) + ______

Physcial Properties During Reaction After Reaction How do you know a reaction took place?

What type of reaction is this? ______

Bonus Information 2. Magnesium and hydrochloric acid

Mg(s) + HCl(aq) MgCl2(aq) + H2(g)

Bonus Information

3. Baking soda (sodium bicarbonate) and citric acid

NaHCO3 + C6H8O7 C6H5Na3O7 + ____ + H2O

What type of reaction is this? ______Bonus Information

4. Lead (II) nitrate and potassium iodide solutions

Lead (II) nitrate and potassium iodide solutions react to produce a precipitate of lead (II) iodide and potassium nitrate solution.

Bonus Information

BONUS REACTION – Hydrolysis of water