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Ch.2 - Atoms, Molecules, and Ions
Brown - Chemistry: The Central Science 15th Edition
Brown15th EditionChemistry: The Central ScienceISBN: 9780137542970Not the one you use?Change textbook
All textbooksBrown 15th EditionCh.2 - Atoms, Molecules, and IonsProblem 79b,c,d,e
Chapter 2, Problem 79b,c,d,e

Write the chemical formula for each substance mentioned in the following word descriptions (use the front inside cover to find the symbols for the elements you do not know). (b) On treatment with hydrofluoric acid, silicon dioxide forms silicon tetrafluoride and water. (use the front inside cover to find the symbols for the elements you do not know). (c) Sulfur dioxide reacts with water to form sulfurous acid. (use the front inside cover to find the symbols for the elements you do not know). (d) The substance phosphorus trihydride, commonly called phosphine, is a toxic gas. (e) Perchloric acid reacts with cadmium to form cadmium(II) perchlorate.

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Step 1: Identify the elements in the compound. In this case, the compound is phosphorus trihydride, which contains the elements phosphorus and hydrogen.
Step 2: The prefix 'tri' in 'trihydride' indicates that there are three atoms of hydrogen for every atom of phosphorus.
Step 3: Write the symbol for each element, followed by the number of atoms of that element in the compound. The symbol for phosphorus is 'P' and the symbol for hydrogen is 'H'.
Step 4: The number of atoms is written as a subscript after the element symbol. Since there is one atom of phosphorus and three atoms of hydrogen, the chemical formula is written as P1H3.
Step 5: If the subscript is 1, it is usually omitted. So, the final chemical formula for phosphorus trihydride, or phosphine, is PH3.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

Chemical Formulas

A chemical formula represents the composition of a substance using symbols for its constituent elements and numerical subscripts to indicate the number of atoms of each element. For example, in phosphine, the formula is written as PH3, indicating one phosphorus atom and three hydrogen atoms.
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Element Symbols

Element symbols are one- or two-letter abbreviations used to represent chemical elements in formulas. Each symbol is unique to an element, such as 'P' for phosphorus and 'H' for hydrogen. Familiarity with these symbols is essential for accurately writing chemical formulas.
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Toxicity of Phosphine

Phosphine (PH3) is a colorless, flammable gas with a characteristic odor, and it is known for its toxicity. Understanding the properties and hazards associated with phosphine is important in chemistry, especially in contexts involving safety and environmental impact.
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Related Practice
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Assume that you encounter the following sentences in your reading. What is the chemical formula for each substance mentioned? (c) Hydrogen cyanide is a very poisonous gas.

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a. What elements are contained in hydrocarbons?

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Give the name or chemical formula, as appropriate, for each of the following binary molecular substances: (f) tetraphosphorus hexasulfide.