Star InactiveStar InactiveStar InactiveStar InactiveStar Inactive
 

The amount of heat absorbed in the formation of solution that contains one mole of solute, the value is positive if heat is absorbed (endothermic) and negative if heat is released (exothermic).

Latest Articles

  • What are Compound Microscopes?

    Most of the microscopes used today are compound. A compound microscope features two or more lenses. A hollow cylinder called the tube connects the two lenses. The top lens, the one people look through, is called the eyepiece. The bottom lens is known as the objective lens. Below the two lenses is...

  • Use of diamonds

    Diamond is a crystalline modification of pure carbon formed in the deep interior of the Earth, in the upper mantle at depths of more than 80-100 kilometers, at exceptionally high pressure and temperature. It is the most precious stone, the hardest and most wear-resistant mineral, the most...

  • Gas of rotten eggs

    If you happen to break a rotten egg, then you know the smell of hydrogen sulfide, because the stench of the spoiled egg depends on of its presence in rotting protein substances.

  • Diamonds Are Forever

    Diamonds are still a girl's best friend, right? We love the shiny gems. They are the most popular rocks sold today. But what exactly are they, anyway? Where do they come from? What else are they used for?

  • Varieties of garnet minerals

    The most famous type of garnet stone is pyrope (flaming). This is the "oldest of garnets", with a dense red color, similar to the grain of an edible garnet. Pyrope has a variety called rhodolite - a stone of dense pink or pink-purple color, which sometimes has the alexandrite effect and is used in...



Most Popular

Flammable

A liquid as defined by NFPD and DOT as having a flash point below 37.8°C (100°F).

Evaporation Rate

The rate at which a particular substance will vapourize (evaporate) when compared to the rate of a known substance such as ethyl ether. This term is especially useful for health and fire-hazard considerations.

Specific Rate Constant

An experimentally determined (proportionality) constant, which is different for different reactions and which changes only with temperature, k in the rate-law expression: Rate = k [A] x [B]v.

Chain Reaction

A reaction that, once initiated, sustains itself and expands. This is a reaction in which reactive species, such as radicals, are produced in more than one step. These reactive species, radicals, propagate the chain reaction.

 

Sigma Orbital

Molecular orbital resulting from head-on overlap of two atomic orbitals.

How to make crystal glass

From history we know that the idea of creating crystal belongs to the British: they were the first to add lead oxides to the charge material, and as a result got glass with unusual “voice”, transparency and sparkling faces. Classical crystal contains 24% of lead oxide, but there are products with a higher content of up to 30%.

Dipole Moment

The product of the distance separating opposite charges of equal magnitude of the charge, a measure of the polarity of a bond or molecule, a measured dipole moment refers to the dipole moment of an entire molecule.

yttrium

A rare trivalent metallic element, found in gadolinite and other minerals. Symbol: Y, at. wt.: 88.905, at. no.: 39, sp. gr.: 4.47. Cf."rare-earth element."

Yttrium has a silver-metallic luster and is relatively stable in air unless finely divided. Turnings of the metal, however, ignite in air if their temperature exceeds 400oC. Yttrium oxide is one of the most important compounds of yttrium and accounts for the largest use. It is widely used in making YVO4 europium, and Y2O3 europium phosphors to give the red color in color television tubes.

Law of Combining Volumes (Gay-Lussac's Law)

At constant temperature and pressure, the volumes of reacting gases (and any gaseous products) can be expressed as ratios of small whole numbers.

 

yttria

Y2O3: A white, water-insoluble powder, Y2O3, used chiefly in incandescent gas and acetylene mantles.