Reaction Prediction

Basics

Research in chemistry involves understanding the properties of reactions.

Predicting the products of a reaction is a central topic in chemistry.

Main Areas of Prediction

• Three main Areas to Reaction prediction:– Activity Series– Combustion– Solubility

Activity Series

Activity SeriesSingle Replacement Reactions

• For some chemical reactions, we will be able to predict whether or not the reaction will happen at all.

• For an element to replace another, the lone element must be more active than the element it is replacing in the substance.

The “Activity Series” of Metals Lithium Potassium Calcium Sodium Magnesium Aluminum Zinc Chromium Iron Nickel Lead Hydrogen (for reference)Hydrogen (for reference) Bismuth Copper Mercury Silver Platinum Gold

Higher activity

Lower activity

The “Activity Series” of Halogens

Fluorine Chlorine Bromine Iodine

Halogens can replace other halogens in compounds, provided they are above the halogen they are trying to replace.

2NaCl(s) + F2(g) 2NaF(s) + Cl2(g)

MgCl2(s) + Br2(g) ??? No Reaction!

???

Higher Activity

Lower Activity

Example: Zn+ 2 HCl ZnCl2 + H2

Example: Thermite Reaction 2 Al + Fe2O3 Al2O3 + 2 Fe

Learning Check

• Use the Activity Series to predict whether the following reaction can occur under normal conditions.

• Mg + CuSO4

• Fe+ CuSO4→

• Ni + NaCl →

• Li + ZnCO3→

• Al + CuCl2→

Will occur

Will occur

Will not occur

Will occur

Will occur

Solution

• Since Magnesium (Mg) is above Copper (Cu). This reaction will occur.

• Iron (Fe) is above Copper (Cu). This reaction will occur. • Nickel (Ni) is below Sodium (Na). This reaction will not

occur.• Lithium (Li) is above Zinc (Zn). This reaction will occur.• Aluminum (Al) is above Copper (Cu). This reaction will

occur.

Parts to the Series Pt. I

• Highly Reactive Group– Potassium through Sodium

• Highly reactive—Will react violently with water or anything containing water (i.e. acids)

• Will react with anything that causes lower groups to react

• Near High• Magnesium and Aluminum

– Violent with Acids and anything causing lower groups to react

– May spontaneously combust if in fine powder

Part II

• Moderately reactive– Zinc through Lead– React with acids (Hydrochloric, Sulfuric, etc.)– Produce Hydrogen gas when reacting with

acids.– Will react with anything that causes lower

groups to react

Part III

• Not very reactive– Copper through Mercury

• Typically will not react• The only acid they will react with is nitric acid (we’ll

talk more about this during the acid/base unit)

• Unreactive– Gold and Platinum

• They’re not inert, but darn close.• Aqua regia (mixture of nitric acid and hydrochloric

acid) will dissolve these metals.

Part IV(That’s a four for those of you that missed that on the exam.)

• Nitric acid (HNO3) will produce nitrogen dioxide as a product along with the appropriate nitrate.

• Carbonates (CO32-) and bicarbonates (HCO3

-) will produce carbon dioxide, water and a salt containing the rest of the elements as products.

• Hydroxides (OH-) tend to form water if hydrogen is present in the reaction.

Part V

• Transition metals keep their charge in double replacement reactions.

• In single replacement, figuring out what charge is a little more difficult.

• Iron=3, Zinc 2, Copper 2, Silver 1

• Metals that react with acids produce the metal salt and hydrogen gas

• Metals reacting with water produce the metal hydroxide and hydrogen gas

Combustion Reactions

3 Types of Combustion

• Hydrocarbon-contains carbon and hydrogen. For predictions, you can ignore oxygen in hydrocarbons. Oxygen still matters when balancing.

• All Combustion reactions involve reacting with oxygen gas.(O2)

Hydrocarbon Combustion

• Complete– Involves an EXCESS of oxygen– Products are always carbon dioxide and water

• Incomplete– Oxygen is LIMITED– Products are carbon monoxide and water– Soot (unburned hydrocarbon) is a byproduct,

but not commonly listed as a product.

Everything else

• Form the oxide– Burning magnesium produces magnesium

oxide– Burning iron produces iron oxides– Burning sulfur produces sulfur dioxide– Burning aluminum produces aluminum oxide

Solubility

Solubility Rules

• Solubility Rules are far more complex than single replacement and combustion reactions.

• We will be spending the next couple of weeks building the necessary information to predict these reactions.

• The rules are not pretty. You have been warned.