BASIC REDOX

In our Chemical Reactions Lab, we added COPPER METAL TO

SILVER NITRATE SOLUTION -

What happened?

The equation for this reaction is:

Cu + 2AgNO3 → 2Ag + Cu(NO3)2

What type of reaction is this?

Lets look closer at what actually happened.

What are the charges on each of the substances below?

(Reminder: Pure elements have no charge)

Cu + 2AgNO3 → 2Ag + Cu(NO3)2

Remember that ionic compounds dissociate in water; so ionic compounds are actually separated in this reaction as follows:

So, if you cross out the substance that didn’t change, you find out the chemical changes that actually happened in this reaction.

You can separate this complete reaction into 2 half-reactions.

In half-reactions: e- stands for _______________

Each copper atom lost ___________electrons. Each of the two silver

ions gained ______ of those _______ electrons.

The number of electrons lost and gained in a reaction must be equal.

What Law demands this?

You can use this fact to help balance difficult equations.

For example: the space shuttle is lifted off the earth by this tough redox reaction:

NH4ClO4 + Al → Al2O3 + HCl + N2 + H2O

Label each of these substances

The copper atoms lost electrons; i.e., they were

The silver atoms gained electrons; i.e., they were

Oxidation is the process in which a substance

_______________electrons.

Reduction is the process in which a substances

__________________electrons.

If you have one of these processes, you must have the other

How will you remember which is oxidation, and which is reduction.

An oxidation-reduction reaction (redox for short) is:

Some “real-life” examples of redox reactions…

Another example of a redox reaction…combustion!

This is a redox process by which your body stores energy. You will

talk about this in biology next year.

This type of reaction is ___________ a redox reaction.

Single replacement Combustion

Combination Decomposition reactions

Double replacement

We will be doing a demonstration that includes

redox reactions. The demo is called the “Hindenburg.”

What do you know about the Hindenburg?

In the early 1930’s, passenger air travel was through dirigibles (giant blimps). They were filled with hydrogen gas, because it is lighter

than air. The Hindenburg (1936) was the “pride” of Nazi Germany – and capable of

crossing the Atlantic Ocean.

What happened to the Hindenburg?

There exists actual historic video footage of what

happened to the Hindenburg – which we’ll

see now!

In our demonstration, we will create a model of the Hindenburg. First, we will do a redox

reaction to generate hydrogen gas by adding aluminum foil to hydrochloric acid. We will use the hydrogen gas to fill a balloon, thus creating

our own little “airship,” circa 1936.

What is the balanced equation for aluminum + hydrochloric acid?

Write the charges over each substance, and the half reactions. What is being oxidized, and what is being reduced?

For each of the following reactions, write the half-reactions and determine which element has been oxidized, and which has been reduced.

1) 3Mg + 2Al(NO3)3 → 3Mg(NO3)2 + 2Al

2) 2Li + CaCl2 → 2LiCl + Ca

3) 6K + 2H3PO4 → 2K3PO4 + 3H2

1) 3Mg + 2Al(NO3)3 → 3Mg(NO3)2 + 2Al

2) 2Li + CaCl2 → 2LiCl + Ca

3. 6K + 2H3PO4 → 2K3PO4 + 3H2

Final note: the reaction which destroyed the Hindenburg was also

a redox reaction!2H2 + O2 → 2H2O