A. Oxygen B. Gold C. Water D. Helium 相关知识点: 试题来源: 解析 C。解析:化合物是由两种或两种以上不同元素组成的纯净物。水(H₂O)是由氢和氧两种元素组成的化合物。A选项氧气(O₂)是单质,由一种元素组成;B选项黄金(Au)是单质;D选项氦气(He)是单质,所以C正确。反馈...
Natural gas resourcescontain the non-renewable compound helium, derived from “helios,” the Greek word for sun. Helium is produced by naturally occurring radioactive materials beneath the earth’s surface. Uranium and thorium are two examples of radioactive elements. Helium rises into the air or ...
The baby's food was a rolled oat mixture sold in general stores - mothers just had to add hot water. Mothers loved the convenience and many babies ate the poisoned food. When people got busy investigating Polio, a false "vaccine" was created to throw people off. Polio was "cured" ...
Is a pure silver ring classified as an element, a compound, a homogeneous mixture, or a heterogeneous mixture? Explain.Matter:In our surroundings, everything is constructed of matter. Every element, compound, and mixture is made up of very small...
soluble salt from a liquid or recover the soluble solid solute from the solution. Crystallization. To separate a solid compound in pure and geometrical form. Sublimation. To separate volatile solids, from a non-volatile solid. Distillation. To separate the constituents of a liquid mixture, which ...
A compound is sometimes confused with amixture, but the two differ in important ways. In a mixture, substances are combined, but there's nochemical reactionor bonding like that found in compounds. The individual substances in a mixture retain their ownpropertiesand can be separated into their ...
Is seawater classified as a mixture or a pure substance? Explain. Describe how to separate water from a mixture of water, alcohol and sand. Is concrete classified as a pure substance (element or compound) or a mixture? Explain. Is gold (Au) classified as a mixture or a pure substance?
The oxygen index of PVC is 48. The oxygen index is the lowest oxygen concentration at which a material will begin to burn when exposed to a mixture of nitrogen and oxygen. A compound with a high limiting oxygen index is difficult to burn. What Happens to PVC in a Fire?
The hydroxy compound is preferably a polyether (although compounds such as hydroxyl-containing polyesters, polyamides and polyamines may also be used). Foaming agents include methylene chloride, water, halofluorocarbons, nitrogen, carbon dioxide, methane, helium and argon. Suitable catalysts for poly...
B. heterogeneous mixture. C. heterogeneous compound. D. homogeneous mixture. Mixture: A mixture contains two or more substances present in it in any ratio. It may be homogeneous or heterogeneous. A homogeneous mixture has a uniform composition throughout ...