Imagine that you find the following instructions in a laboratory procedure: “Transfer
1.5 of your sample to a 100 volumetric flask, and dilute to volume.” How do you do this? Clearly these instructions are incomplete since the units of measurement are not stated. Compare this with a complete instruction: “Transfer 1.5 g of your sample to a 100-mL volumetric flask, and dilute to volume.” This is an instruction that you can easily follow. Measurements usually consist of a unit and a number expressing the quantity of that unit. Unfortunately, many different units may be used to express the same ...... more
is an organic base and a trimer of cyanamide, with a 1,3,5-triazine skeleton. Like cyanamide, it contains 66% nitrogen by mass and, if mixed with resins, has fire retardant properties due to its release of nitrogen gas when burned or charred, and has several other industrial uses.
Melamine is combined with formaldehyde to produce melamine resin, a very durable thermosetting plastic used in Formica, and melamine foam, a polymeric cleaning product. The end products include countertops, dry erase boards, fabrics, glues, housewares and flame retardants. Melamine is one of the major components in Pigment Yellow 150, a colorant in inks and plastics. Melamine also enters the fabrication of melamine poly-sulfonate used as superplasticizer for making high-resistance concrete ...... more
Chemical changes take place through chemical reactions. Chemical symbols are used to write chemical reactions in a chemical equation. For example, when a mixture of hydrogen gas (H2) and oxygen gas (O2) ignites, the hydrogen and oxygen combine to form water. A chemical equation expressing the combination of hydrogen and oxygen to form water is
Let’s examine the chemical equation above more closely. Hydrogen and oxygen are written as molecules rather than atoms. Hydrogen, oxygen, and a number of other gases (Cl2, N2, Br2, I2) exist in their natural state as
diatomic (two atoms) molecules. The reason for this diatomic form becomes apparent after we discuss electron configuration and bonding. The plus sign in the equation means “reacts with.” The equation states a molecule of hydrogen reacts with a molecule of oxygen to yield a water molecule ..... more
With the discovery of the neutron, a basic atomic model consisting of three fundamental subatomic particles was complete. While discoveries were being made on the composition of atoms, models were advanced concerning the structure of the atom. John Dalton considered atoms to be solid spheres. In the mid-1800s, one theory considered atoms to consist of vortices in an ethereal continuous fluid. J.J. Thomson put forth the idea that the negative electrons of atoms were embedded in a positive sphere. Thomson’s model was likened to raisins representing electrons in a positive blob of pudding; the model was termed the “plumpudding” model as shown in Figure 4.3. The negative and positive parts of the atom in Thomson’s model canceled each other, resulting in a neutral atom. A clearer picture of the atom began to emerge toward the end of the first decade of the twentieth century ......more.
(devil)Spectroscopy is basically an experimental subject and is
concerned with the absorption,emission or scattering of electromagnetic radiation by atoms or molecules. As we shall see in, electromagnetic radiation covers a wide wavelength range, from radio waves to g-rays, and the atoms or molecules may be in the gas, liquid or solid phase or, of great importance in surface chemistry, adsorbed on a solid surface. reead more
The principal quantum number symbolized by the letter n. The principal quantum number tells which shell the electron is in and can take on integral values starting with 1. The higher the principal quantum number, the farther the orbital is from the nucleus. A higher principal quantum number also indicates a higher energy level. Letters may also be used to designate the shell. Orbitals within the same shell have the same principal quantum number read more.
All corrosion of steel in soil or water is electro-chemical in its origin and nature. There are certain conditions which must be met before a corrosion cell can function. They are: 1. There must be anodes (which are at higher potential) and cathodes (which are at higher potential). 2. There must be an electrical potential can result from a variety of conditions of pipelines read more.
Atomic Structure With the discovery of the neutron, a basic atomic model consisting of three fundamental subatomic particles was complete. While discoveries were being made on the composition of atoms, models were advanced concerning the structure of the atom. John Dalton considered atoms to be solid spheres. In the mid-1800s, one theory considered atoms to consist of vortices in an ethereal continuous fluid read more
