Fundamental Chemical Laws and Gas Properties
Laws of Chemical Combination
Weight Laws
- Law of Conservation of Mass (Lavoisier): In any chemical process, the mass of the reactants must equal the mass of the products of the reaction.
- Law of Constant Proportions (Proust): When two elements come together to form a compound, they do so in a fixed mass ratio.
- Law of Multiple Proportions (Dalton): When two elements combine to form more than one compound, the amounts of one of them that are combined with a fixed amount of the second bear a simple whole number relationship to each other.
- Law of Combining Volumes (Gay-Lussac): The volumes of gases taking part in a chemical reaction show simple whole number ratios to one another when those volumes are measured at the same temperature and pressure.
Gas Laws
- Boyle’s Law (constant temperature): If pressure increases, volume decreases. If pressure decreases, volume increases. PV = constant. The pressure exerted by a gaseous mass is inversely proportional to the volume it occupies.
- Charles’s Law (constant pressure): The volume of a fixed mass of gas at constant pressure varies directly with the Kelvin temperature.
Fundamental Equation of Gases
PV = nRT, PM = dRT
Solutions
Dissolution: A solution is a homogeneous mixture (the components are indistinguishable to the naked eye) of two or more substances.
Concentration
- g/L: grams of solute per liter of solution.
- Molarity (M): moles of solute per liter of solution.
- %: grams of solute per 100g of solution.
Chemical Bonds
Ionic Bond
This bond takes place between atoms of very different electronegativity, between a metal and a non-metal. A non-metal losing electrons is called a cation, and when attached to a metal, it is called an anion.
Properties
- They are crystalline solids.
- They have high melting and boiling points.
- They are hard.
- They are usually soluble in water.
- In a solid state, they will not conduct electricity.
- When molten or in an aqueous solution, they are good conductors of current.
Covalent Bond
It is established between non-metals by sharing pairs of electrons. (Dot plot)
Properties
- They consist of molecules.
- They are usually gases or liquids.
- They have low melting and boiling points.
- They are often poorly soluble in water.
- They are poor conductors of current.
Metallic Bond
It is a very orderly and compact arrangement of positive metal ions, which are distributed among the electrons lost by each atom, forming an “electron cloud”.
Properties
- They are solid at room temperature, except for mercury.
- They have high melting and boiling temperatures.
- They are good conductors of heat and electricity.
- They have ductility and malleability.
Periodic Properties
- Ionization Energy: The energy that must be supplied to a neutral atom in a gaseous state to remove an electron from its outer level.
- Electron Affinity: The energy given off by a neutral atom in a gaseous state when it captures an electron and becomes a mononegative anion. (Halogens have the highest electron affinity).
- Electronegativity: The magnitude that reflects the tendency of atoms to attract electrons towards themselves in a bond where those atoms are joined to others.