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Ch.3 - Molecules, Compounds & Chemical Equations
Chapter 3, Problem 53a,b,c

Write the formula for each acid. a. hydrofluoric acid b. hydrobromic acid c. sulfurous acid

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1. The prefix 'hydro-' in the name of an acid indicates that it is a binary acid, which means it contains only two elements: hydrogen and one other element.
2. The 'fluoric' part of the name 'hydrofluoric acid' comes from the element fluorine. In the names of binary acids, the second element's name is modified to end with '-ic'.
3. Binary acids are named using the format 'hydro-<root>-ic acid', where <root> is the root of the name of the non-hydrogen element. So, 'hydrofluoric acid' means the acid is composed of hydrogen and fluorine.
4. In a binary acid, hydrogen is positively charged (H+) and the other element is negatively charged. In this case, fluorine becomes fluoride (F-) when it gains an electron.
5. Therefore, the formula for hydrofluoric acid is HF, which is the combination of H+ and F- ions.

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Key Concepts

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

Acids and Their Formulas

Acids are substances that can donate protons (H+) in a solution. The formula of an acid typically starts with hydrogen (H) followed by the anion. For example, hydrofluoric acid is derived from hydrofluoride, where the hydrogen is combined with the fluoride ion (F-). Understanding how to derive the formula from the name is essential for identifying acids.
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Naming Conventions for Acids

The naming of acids depends on the anion present. If the anion ends in '-ide', the acid name begins with 'hydro-' and ends with '-ic' (e.g., fluoride to hydrofluoric acid). If the anion ends in '-ate', the acid name ends with '-ic', and if it ends in '-ite', it ends with '-ous'. This systematic approach helps in accurately writing the formulas for various acids.
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Chemical Formula Representation

Chemical formulas represent the composition of a substance using symbols for elements and numerical subscripts to indicate the number of atoms. For hydrofluoric acid, the formula is HF, indicating one hydrogen atom and one fluorine atom. Understanding how to read and write chemical formulas is crucial for communicating chemical information effectively.
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