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The structure of the molecule of urea is O=C(−NH 2) 2.The urea molecule is planar when in a solid crystal because of sp 2 hybridization of the N orbitals. [8] [9] It is non-planar with C 2 symmetry when in the gas phase [10] or in aqueous solution, [9] with C–N–H and H–N–H bond angles that are intermediate between the trigonal planar angle of 120° and the tetrahedral angle of 109.5°.
An example of when impurities are wanted is shown in gems. These gems have slight impurities that act as chromophores and give the stone its color. An example is the gem family beryl which has the base chemical formula of Be 3 Al 2 (SiO 3) 6. Pure beryl will appear colorless but this rarely occurs and the presence of trace elements change its ...
This is the list of extremely hazardous substances defined in Section 302 of the U.S. Emergency Planning and Community Right-to-Know Act (42 U.S.C. § 11002). The list can be found as an appendix to 40 CFR 355. [1] Updates as of 2006 can be seen on the Federal Register, 71 FR 47121 (August 16, 2006). [2]
Hazard statements form part of the Globally Harmonized System of Classification and Labelling of Chemicals (GHS). They are intended to form a set of standardized phrases about the hazards of chemical substances and mixtures that can be translated into different languages.
The use of personal protective equipment may substantially reduce the risk of adverse health effects from contact with hazardous materials. [2] Long-term exposure to chemical hazards such as silica dust, engine exhausts, tobacco smoke, and lead (among others) have been shown to increase risk of heart disease, stroke, and high blood pressure. [3]
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n.o.s. = not otherwise specified meaning a collective entry to which substances, mixtures, solutions or articles may be assigned if a) they are not mentioned by name in 3.2 Dangerous Goods List AND b) they exhibit chemical, physical and/or dangerous properties corresponding to the Class, classification code, packing group and the name and description of the n.o.s. entry [2]
Naturally occurring radioactive materials (NORM) and technologically enhanced naturally occurring radioactive materials (TENORM) consist of materials, usually industrial wastes or by-products enriched with radioactive elements found in the environment, such as uranium, thorium and potassium and any of their decay products, such as radium and radon. [1]