Ch4 Lec 7

Welcome to your first online lecture. Get your notepad out and write on top...Chapter 4, Lecture 7 (Review/Copper Cycle Lab/Molarity).

When we started Chapter 4: Reactions in Aqueous Solutions on 2/24/20, we discussed that there were 3 types of reactions that we were going to cover:

- Section 4.2: Precipitation Reactions, including ionic equations, and net ionic equations,

- Section 4.3 Acid-Base Reactions including neutralization rxn and gas forming reactions, and

- Section 4.4: Oxidation Reduction Reactions including 1/2 rxns, assigning oxidation numbers, LEO-GER...and more!

Review

- Let's review...please write the term in your notes and then a short definition for the following:

1) Solute

2) Solvent

3) Solution

4) Electrolyte

5) Non-electrolyte

6) Strong electrolyte

7) Weak electrolyte

Precipitation Reactions

- Write a short definition of what a precipitation reaction is...

- I did a demonstration in class were i reacted lead nitrate with potassium iodide. I technically started with solids of each of these reactants, but "pushed" them into the large drop of water turning them into aqueous solutions...pls write out this chemical reaction in your notes...(remember a ppt rxn generates a solid/insoluble product - this is when we use our solubility table)

- Write out the ionic equation for the demonstration rxn...

- Wite out the net ionic equation for the demonstration rxn..

- If you did your homework (assigned in class, not WA) from before, then you will have a sheet with 5 precipitation reactions. Please include this sheet in your online notes or if you never did it, here is the worksheet to complete.

Acid-Base Reactions

- Write in your notes the chemical formulas for the following acids:

• Hydrochloric acid -->
• Nitric Acid -->
• Sulfuric Acid -->
• Phosphoric Acid -->

- What make the above chemicals acids?

- Write in your notes the chemical formula or the following bases:

• Sodium hydroxide -->
• Magnesium hydroxide -->
• Potassium hydroxide -->
• Ammonia -->

- What makes these chemicals bases?

- What is the chemical formula for the hydronium ion and write out a reaction showing this as a product...

- There are two types of acid-base reactions we discussed in class:

1) Neutralization Rxn, and

2) Gas forming Rxn.

Neutralization Rxn

- Write in your notes an example of a neutralization rxn...balance and include physical states.

- Now write out the ionic equation for this neutralization rxn...

- Now write out the net ionic equation for this neutralization rxn...

NOTE: all acid-base neutralization rxns have the same net ionic eq.

Gas Forming Rxn

- if a acid-base reaction involves the following ions, then it produces the stated gas:

• HCO₃^- (aq) --> CO₂ (g)
• CO₃^2- --> CO₂ (g)
• SO₃^2- (sulfite) --> SO₂ (g)
• S^2- (sulfide)--> H₂S (g) (rotten eggs)

Write out the following reactions: - aqueous sodium hydrogen carbonate (bicarbonate) with aqueous hydrobromic acid... (products are water, salt, gas)

- aqueous lithium sulfite with aqueous hydrofluoric acid...

- aqueous potassium sulfide with aqueous hydrochloric acid...

Oxidation-Reduction Reactions

LEO --> Loss of Electron is Oxidation

GER --> Gain of Electron is Reduction

Practice assigning oxidation numbers to each element in the following compounds:

- HCl

- H₂O

- H₂, O₂, N₂, Cl₂

- CO₂

-CH₄

-H₂S

-NO₃^- (nitrate ion)

CH₃OH

- Write out the 1/2 reactions for the reaction between Mg (s) and O₂ (g), start by writing out the reaction:

oxidation 1/2 reaction -->

reduction 1/2 reaction -->

In class we discussed 4 different types of oxidation-reduction rxne (Redox rxn):

Combination Rxn

Give an example of a combination rxn, write out the balanced chemical rxn, identify the oxidation numbers of all elements, then indicate the number of electrons involved in the reaction.

Combustion Rxn

Give an example of a combustion rxn, write out the balanced chemical rxn, identify the oxidation numbers of all elements, then indicate the number of electrons involved in the reaction.

Displacement Rxn

Give an example of a displacement rxn, write out the balanced chemical rxn, identify the oxidation numbers of all elements, then indicate the number of electrons involved in the reaction.

Decomposition/disproportionation Rxn

Give an example of a decomposition rxn, write out the balanced chemical rxn, identify the oxidation numbers of all elements, then indicate the number of electrons involved in the reaction.

***NOW...go to WA and do assignment HW 4.1 Spring 2020 (Oxidation Numbers) <--not available until mon at 8 am***

END of Ch 4, Lecture 7