STOICHIOMETRY (Quantitative Chemistry)

Today we learned about Stoichiometry. I know the word sounds a little bizarre and frightening but its really not!

Stoichiometry is a branch of chemistry that deals with the quantitative (numbers) analysis of chemical reactions.

• It is a generalization of mole conversions to chemical reactions
• understanding the 6 types of chemical reactions is the basis of stoichiometry

THE 6 TYPES OF REACTIONS:

1. Synthesis (formation)
2. Decomposition
3. Single Replacement (SR)
4. Double Replacement (DR)
5. Neutralization
6. Combustion

We shall now go through each reaction in further detail.... ready?

^Your reaction will soon change

SYNTHESIS:

A synthesis reaction is when two or more simple compounds combine to form a more complicated one. These reactions come in the general form of: 

A + B ---> AB

DECOMPOSITION:

A decomposition reaction is the opposite of a synthesis reaction - a complex molecule breaks down to make simpler ones. These reactions come in the general form:

AB ---> A + B

Example: 2 H₂O ---> 2 H₂ + O

_{SINGLE REPLACEMENT:}

This is when one element trades places with another element in a compound. These reactions come in the general form of:

A + BC ---> AC + B (A IS A METAL)

OR

A +BC---> C+ BA (A IS A NON-METAL)

One example of a single replacement reaction is when magnesium replaces hydrogen in water to make magnesium hydroxide and hydrogen gas:

Mg + 2 H₂O ---> Mg(OH)₂ + H₂

_{DOUBLE REPLACEMENT:}

 This is when the anions and cations of two different molecules switch places, forming two entirely different compounds. These reactions are in the general form:

AB + CD ---> AD + CB

One example of a double displacement reaction is the reaction of lead (II) nitrate with potassium iodide to form lead (II) iodide and potassium nitrate:

Pb(NO₃)₂ + 2 KI ---> PbI₂ + 2 KNO₃

                               CaSO₄ + Mg(OH)₂ --> Ca(OH)₂ + MgSO_{4
*remember that in double replacement reactions, the metal always go first! in the example of:
AgNO3 + NaCL ---> AgCl +NaNO3}

_{Na is the metal and NO3 is the non-metal even though the order is AB+ CD --> AD+ BC we would think that NO}

_{3 goes first but it doesnt!}

_{NEUTRALIZATION:}

Also known as Acid-base neutralization: This is a special kind of double displacement reaction that takes place when an acid and base react with each other. The H⁺ion in the acid reacts with the OH^- ion in the base, causing the formation of water. Generally, the product of this reaction is some ionic salt and water (note water can be written as HOH):

HA + BOH ---> H₂O + BA

One example of an acid-base reaction is the reaction of hydrobromic acid (HBr) with sodium hydroxide:

HBr + NaOH ---> NaBr + H₂O

COMBUSTION:

A combustion reaction is when oxygen combines with another compound to form water and carbon dioxide. These reactions are exothermic, meaning they produce heat. An example of this kind of reaction is the burning of napthalene:

C₁₀H₈ + 12 O₂ ---> 10 CO₂ + 4 H₂O

_{See that wasn't so hard now was it? High five for effort... lol}

 _{Here are a couple of questions for you to try! List what type of reactions they are. The answers are on the bottom.}

1. Na₂CO₃ --> Na₂O + CO₂
2.  _{Pb + O2 --> PbO2}
3. _{CH4 + 2 O2 --> CO2 + 2 H2O}
4. _{NH4OH + HBr --> H2O + NH4Br}
5. _{CaSO4 + Mg(OH)2 --> Ca(OH)2 + MgSO4}
6. _{2 Fe + 6 NaBr --> 2 FeBr3 + 6 Na}

answers:

1. Decomposition
2. Synthesis
3. Combustion (see the carbon dioxide and water?)
4. Acid-Base Neutralization (see the water?)
5. double replacement
6. Single replacement (where A is a metal)

yay! heres another video for your enjoyment:

post by ren flores