China
Africa
Explore chapters and articles related to this topic
Electric Power Generation
Published in A.J. Pansini, K.D. Smalling, Guide to Electric Power Generation, 2020
Chemical symbols and equations convey much information in a condensed form. Chemical combinations may be written as equations in which, for convenience, symbols are used to represent different elements. Thus, for the gaseous elements mentioned above: O represents one atom of oxygen, H one atom of hydrogen, and N one atom of nitrogen. As indicated above, molecules of gaseous elements each contain two atoms and are represented by O2; H2; and N2. Molecules of non-gaseous elements may consist of a single atom; for example, carbon represented by C, sulphur by S, etc.
Gas Power Cycles
Published in Irving Granet, Jorge Luis Alvarado, Maurice Bluestein, Thermodynamics and Heat Power, 2020
Irving Granet, Jorge Luis Alvarado, Maurice Bluestein
The numbers in front of the chemical symbols indicate the number of molecules of each needed to balance the chemical equation. Thus, the equation may also be read as the number of moles of each for the complete combustion of octane into its products. From this, it is seen that 25 moles of oxygen is required to burn two moles of octane, or 12.5 per mole of fuel. From Chapter 7, a mole of air contains 21% oxygen, so 1 mole of oxygen requires 4.76 moles of air. Thus, 12.5 moles of oxygen requires 59.5 moles of air, yielding an air–fuel (AF) ratio of 59.5 by volume. To convert this ratio into a mass ratio, the molecular weights of the gases, as given in Chapter 7, can be used. The AF ratio is important in evaluating the effectiveness of the combustion process. For the typical Otto engine cycle, the AF ratio by mass is around 15.
Cells and batteries
Published in Adrian Waygood, An Introduction to Electrical Science, 2013
A chemical symbol is used to identify a particular element. For example, the symbol H represents hydrogen, Zn represents zinc, and so on. Combinations of these symbols represent compounds, with numeric subscripts indicating the presence of two or more atoms of an element. For example, the chemical symbol for (the compound) water, is H2O, which indicates a molecule comprising two atoms of hydrogen and one atom of oxygen.
Chemical and other aspects of Rutherford’s nuclear atom
Published in Journal of the Royal Society of New Zealand, 2021
In 1912 niton and its symbol Nt was accepted by The International Commission for Atomic Weights, but in 1923 the isotope was officially renamed radon, chemical symbol Rn. Only in 1957 did IUPAC elevate radon from the name of an isotope to the name of an element. Earlier claims that radon was discovered in 1900 by the German chemist Ernst Dorn have proved to be unfounded, and today it is customary to credit Ramsay and Whytlaw-Gray with the discovery (Weeks and Leicester 1967, pp. 785–786; Marshall and Marshall 2003). However, the discovery process is rather confusing and Rutherford certainly had an important share in it. Indeed, it has been claimed that credit for the discovery belongs to him and no-one else (Marshall and Marshall 2003). On the other hand, Rutherford never himself claimed to have discovered radon. In an address of 1934 to the Chemical Society, he reminisced: ‘I look back with some pride to the fact that Soddy and I were able to prove that the radium emanation must belong to the group of inert gases, although the amount of emanation available for our experiments was less than c.c. [cubic centimetre]’ (Rutherford 1934, p. 636).
Energetic aspects of elemental boron: a mini-review
Published in Energy Sources, Part A: Recovery, Utilization, and Environmental Effects, 2022
Okan Icten, Birgul Zumreoglu-Karan
Boron is a chemical element with chemical symbol B and atomic number 5. Boron never occurs as a free element on Earth but is found in minerals as borate salts in different proportions. Chemically uncombined boron in black crystalline form is challenging to obtain because of its high melting point (2077°C) and the highly corrosive nature of liquid boron. The energy required to recover boron from ore is intense due to the B-O bond’s high bond enthalpy (806 kJ mol–1). Elemental boron is not considered to be toxic. In its pure crystalline form, it is chemically inert.