Organic Compounds

The chemical compounds of living things are known as organic compounds because of their association with organisms. Organic compounds, which are the compounds associated with life processes, are the subject matter of organic chemistry. Among the numerous types of organic compounds, four major categories are found in all living things: carbohydrates, lipids, protein, and nucleic acids.

Carbohydrates

Almost all organisms use carbohydrates as sources of energy. In addition, some carbohydrates serve as structural materials. Carbohydrates are molecules composed of carbon, hydrogen, and oxygen; the ratio of hydrogen atoms to oxygen atoms is 2:1.

Complete information on 9 different types of Glasses

Glass is a mixture having no definite boiling of freezing points. It is also called a super cooled liquid. Chemically, most glasses are silicates. It is transparent and not affected by chemicals. It can be moulded into any shape. The ingredients for making glass are:-

1. Limestone (CaCO₃),

2. Soda ash (Na₂CO₃), and

3. Sand (SiO₂)

Manufacture of glass

The manufacture of glass involves the following steps:

1. Limestone, sand and soda ash are mixed and poured into a tank furnace. Tank furnace looks like a small swimming pool. It is very hot (about 1700⁰C). It is shallow at one end and deep at the other.

2. The raw material moves slowly towards the deeper end. Silica melts at a very high temperature. In order to lower its melting point, soda ash is added. Thus, energy is saved and a low cost is incurre

Diffusion

If someone is cooking in the kitchen it doesn't take long for the smell to travel around the house to other rooms. This is because of diffusion.

Diffusion in gases

When chemicals, like the smell of perfume or burning toast, are let loose in a room, the particles mix with the air particles. The particles of smelly gas are free to move quickly in all directions. They eventually spread through the whole room. This is called diffusion.

You don't have to mix the gases by waving your arms around - it mixes on its own. Diffusion in gases is quick because the particles in a gas move quickly. It happens even faster in hot gases

Diffusion happens quickly in gases.

Diffusion in liquids

Diffusion can also happen in liquids. This is because the particles in liquids can move around each other, which means that eventually they are evenly mixed.

For example if you drop a little bit of paint into a jar of water the colour will spread slowly through the water. This is by diffusion.

Diffusion in liquids is slower than diffusion in gases because the particles in a liquid move more slowly.

Solids

Diffusion does not happen at all in solids because the particles in a solid can only vibrate on the spot, rather than being able to move from place to place.

Chemical Bonding

Chemical compounds are formed by the joining of two or more atoms. A stable compound occurs when the total energy of the combination has lower energy than the separated atoms. The bound state implies a net attractive force between the atoms ... a chemical bond. The two extreme cases of chemical bonds are:

Covalent bond: bond in which one or more pairs of electrons are shared by two atoms.

Ionic bond: bond in which one or more electrons from one atom are removed and attached to another atom, resulting in positive and negative ions which attract each other.

Other types of bonds include metallic bonds and hydrogen bonding. The attractive forces between molecules in a liquid can be characterized as van der Waals bonds.

Sodium chloride Ionic

Hydrogen molecule Covalent

Chemical Bond Types

Ionic Bonds

An ionic bond is formed by the attraction of oppositely charged atoms or groups of atoms. When an atom (or group of atoms) gains or loses one or more electrons, it forms an ion. Ions have either a net positive or net negative charge. Positively charged ions are attracted to the negatively charged 'cathode' in an electric field and are called cations. Anions are negatively charged ions named as a result of their attraction to the positive 'anode' in an electric field.

Every ionic chemical bond is made up of at least one cation and one anion.

Ionic bonding is typically described to students as being the outcome of the transfer of electron(s) between two dissimilar atoms. The Lewis structure below illustrates this concept.

For binary atomic systems, ionic bonding typically occurs between one metallic atom and one nonmetallic atom. The electronegativity difference between the highly electronegative nonmetal atom and the metal atom indicates the potential for electron transfer.

Covalent bond

"Covalent" redirects here. For other uses, see Covalent (disambiguation).

A covalent bond forming H₂ (right) where two hydrogen atoms share the two electrons

A covalent bond is a chemical bond that involves the sharing of electron pairs between atoms. The stable balance of attractive and repulsive forces between atoms when they share electrons is known as covalent bonding.For many molecules, the sharing of electrons allows each atom to attain the equivalent of a full outer shell, corresponding to a stable electronic configuration.

Covalent bonding includes many kinds of interactions, including σ-bonding, π-bonding, metal-to-metal bonding,agostic interactions, and three-center two-electron bonds. The term covalent bond dates from 1939.The prefix co- means jointly, associated in action, partnered to a lesser degree, etc.; thus a "co-valent bond", in essence, means that the atoms share "valence", such as is discussed in valence bond theory. In the molecule H
2, the hydrogen atoms share the two electrons via covalent bonding.Covalency is greatest between atoms of similar electronegativities. Thus, covalent bonding does not necessarily require that the two atoms be of the same elements, only that they be of comparable electronegativity. Covalent bonding that entails sharing of electrons over more than two atoms is said to be delocalized.

Contents

  

• 1 History
• 2 Physical properties of covalent compounds (polar and non-polar)
• 3 Polarity of covalent bonds
• 4 Subdivision of covalent bonds
• 5 Sources
• 6 External links

Biochemical Energetics

The free energy change (DG) of a reaction determines its spontaneity. The free energy change (DG), and its relation to equilibrium constant, are discussed on p. 57-59 of Biochemistry 3rd Edition by Voet & Voet. A reaction is spontaneous if DG is negative (if the free energy of the products is less than the free energy of the reactants).

DG = change in free energy, DGo' = standard free energy change (with 1 M reactants and products, at pH 7), R = gas constant, T = absolute temperature.

Note that the standard free energy change (DG^o') of a reaction may be positive, for example, and the actual free energy change (DG) negative, depending on cellular concentrations of reactants and products. Many reactions for which DG^o' is positive are spontaneous because other reactions cause depletion of products or maintenance of high substrate concentrations.

At equilibrium, DG equals zero. Solving for DGo' yields the relationship at left.K'eq, the ratio [C][D]/[A][B] at equilibrium, is called the equilibrium constant. An equilibrium constant greater than one (more products than reactants at equilibrium) indicates a spontaneous reaction (negative DG�').

The variation of equilibrium constant with DG^o' is shown in the table below.

Unique Features of Aqueous Solutions

An aqueous solution is one that is occurring in water. What makes water significant is that it can allow for substances to dissolve and/or be dissociated into ions within it.

Electrolytes

Water is generally the solvent found in aqueous solution, where a solvent is the substance that dissolves the solute. The solute is the substance or compound being dissolved in the solvent. A solute has fewer number of particles than a solvent, where it's particles are in random motion. Interestingly, aqueous solutions with ions conduct electricity to some degree. Pure water, having a very low concentration of ions, cannot conduct electricity. When a solute dissociates in water to form ions, it is called an electrolyte, due to the solution being a good electrical conductor. When no ions are produced, or the ion content is low, the solute is a non-electrolyte. Non-electrolytes do not conduct electricity or conduct it to a very small degree. In an aqueous solution a strong electrolyte is considered to be completely ionized, or dissociated, in water, meaning it is soluble. Strong acids and bases are usually strong electrolytes. A weak electrolyte then is considered to be one that is not completely dissociated, therefore still containing whole compounds and ions in the solution. Weak acids and bases are generally weak electrolytes. In other words, strong electrolytes have a better tendency to supply ions to the aqueous solution than weak electrolytes, and therefore strong electrolytes create an aqueous solution that is a better conductor of electricity. 

Things to note:

• Most soluble ionic compounds and few molecular compounds are strong electrolytes.
• Most molecular compounds are weak or non electrolytes.

Table of Contents

1. 1. Electrolytes
2. 2. Ion Concentrations
3. 3. Precipitation Reactions
4. 4. Acid Base Reactions
5. 5. Problems
6. 6. Contributors 
7. 
   

   Example 1

   Here's an example of MgCl2 in water: MgCl2→Mg2+(aq)+2Cl−(aq) The ionic compound dissociates completely to form ions in water, therefore, it is a strong electrolyte.  Now let's look at a weak electrolyte: HC2H3O2(aq)⇌H+(aq)+C2H3O−2(aq) The ionic compound, HC2H3O2 in this situation, only partially dissociates, as expressed by the double arrows in the reaction. This means that the reaction is reversible and never goes to completion. The H+ cation is a proton that interacts with the H2O molecules that it is submerged in. The interaction is called hydration. The actual H+ ion does not exist in the aqueous solution. It is the hydronium ion, H3O+ that interacts with water to create additional species like H5O+2, H9O+4, and H7O+3. H3O+ can simply be described as the hydration of one H+ and one water molecule. For nonelectrolytes, all that needs to be done is write the molecular formula because no reaction or dissociation occurs. One example of a nonelectrolyte is sugar: written as C6H12O6(aq).