Lesson 6 Molecular Compounds - Naming and Formulas
Acidic Compounds
Did you know that one factor that affects the colour of hydrangea blooms is the acidity of the soil?
Acidic compounds are a special class of compounds with special properties and a unique naming process. Acid-forming compounds can be recognized by their chemical formula: H is written first in the formula, for example, HCl, H2SO4,
H
3PO4.
The process of naming acids is to first identify the name as if the substance was an ionic compound. Then convert that name into an acid name using a pattern.
The process of naming acids is to first identify the name as if the substance was an ionic compound. Then convert that name into an acid name using a pattern.
| Solutions of Compounds Named |
Classical Acid Name |
|---|---|
| hydrogen ___ide | hydro____ic acid |
| hydrogen ___ate | ____ic acid |
| hydrogen ___ite | ____ous acid |
Note: Acids that contain phosphorus have “or” added in for the acid name, and acids that contain sulfur have “ur” added in for the acid name.
| Formula | Solutions of Compounds Named |
Classical Acid Name |
|---|---|---|
| HCl | hydrogen chloride | hydrochloric acid |
| H3PO4 | hydrogen phosphate | phosphoric acid |
| H2SO3 | hydrogen sulfite | sulfurous acid |
Examples
Work through the following examples to gain a better understanding of acid nomenclature. Each example has a video to go with it. To play the video, click on the play icon next to the example.Identify the type of compound.
Hydrogen written first and bonded to a non-metal indicates it is an acid-forming compound.
Provide a name for the compound based on previously learned rules.
hydrogen fluoride
Using the rules for naming acids, determine the classical acid name.
hydrofluoric acid
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/kujlvc0jq7
Identify the type of compound.
Hydrogen written first and bonded to a polyatomic indicates it is an acid-forming compound.
Provide a name for the compound based on previously learned rules.
hydrogen perchlorate
Using the rules for naming acids, determine the classical acid name.
perchloric acid
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/7j29kacbdi
Identify the type of compound.
Hydrogen written first and bonded to a polyatomic indicates it is an acid-forming compound.
Provide a name for the compound based on previously learned rules.
hydrogen chlorite
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/uxeo1bv4wa
The acids you have studied thus far are all inorganic acids; however, there are also organic acids. The formulas of organic acids can be recognized by the ending “–COOH.” Examples:
ethanoic acid, also called acetic acid, and as a dilute solution called vinegar
CH3COOH
methanoic acid, also known as formic acid—the substance found in bee strings and ants
HCOOH
ethanoic acid, also called acetic acid, and as a dilute solution called vinegar
CH3COOH
methanoic acid, also known as formic acid—the substance found in bee strings and ants
HCOOH
To determine the formula of an acid, use the pattern to convert the acid name into an ionic name and write a proper formula taking charges on the ions into consideration.
Examples
Work through these examples to gain a deeper understanding of writing formulas for acids. Each example has a video to go with it. To play the video, click on the play icon next to the example.Using the rules for naming acids, determine the compound name.
nitrous acid = hydrogen nitrite
Write the ion symbols.
«math»«msup»«mi mathvariant=¨normal¨»H«/mi»«mo»+«/mo»«/msup»«mo»§#160;«/mo»«msubsup»«mi»NO«/mi»«mn»2«/mn»«mo»-«/mo»«/msubsup»«/math»
Determine the lowest common multiple of the two ions.
The lowest common multiple between 1 and 1 is 1.
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/crfhnia1mo
Using the rules for naming acids, determine the compound name.
carbonic acid = hydrogen carbonate
Write the ion symbols.
«math»«msup»«mi mathvariant=¨normal¨»H«/mi»«mo»+«/mo»«/msup»«mo»§#160;«/mo»«mo»§#160;«/mo»«msubsup»«mi»CO«/mi»«mn»3«/mn»«mrow»«mn»2«/mn»«mo»-«/mo»«/mrow»«/msubsup»«/math»
«math»«msup»«mi mathvariant=¨normal¨»H«/mi»«mo»+«/mo»«/msup»«mo»§#160;«/mo»«mo»§#160;«/mo»«msubsup»«mi»CO«/mi»«mn»3«/mn»«mrow»«mn»2«/mn»«mo»-«/mo»«/mrow»«/msubsup»«/math»
Determine the lowest common multiple of the two ions.
The lowest common multiple between 1 and 2 is 2.
Determine the factor to multiple each ion by.
«math»«mtable columnspacing=¨0px¨ columnalign=¨right center left¨»«mtr»«mtd»«msup»«mi mathvariant=¨normal¨»H«/mi»«mo»+«/mo»«/msup»«mo»§#160;«/mo»«mo»§#215;«/mo»«mo»§#160;«/mo»«mn»2«/mn»«mo»§#160;«/mo»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»§#160;«/mo»«mn»2«/mn»«mo»+«/mo»«/mtd»«/mtr»«mtr»«mtd»«msubsup»«mi»CO«/mi»«mn»3«/mn»«mrow»«mn»2«/mn»«mo»-«/mo»«/mrow»«/msubsup»«mo»§#160;«/mo»«mo»§#215;«/mo»«mo»§#160;«/mo»«mn»1«/mn»«mo»§#160;«/mo»«/mtd»«mtd»«mo»=«/mo»«/mtd»«mtd»«mo»§#160;«/mo»«mn»2«/mn»«mo»§#8211;«/mo»«/mtd»«/mtr»«/mtable»«/math»
This will create a neutral compound.
The ratio of «math»«/math»«math»«msup»«mi mathvariant=¨normal¨»H«/mi»«mo»+«/mo»«/msup»«mo»§#160;«/mo»«mi»to«/mi»«mo»§#160;«/mo»«msubsup»«mi»CO«/mi»«mn»3«/mn»«mrow»«mn»2«/mn»«mo»-«/mo»«/mrow»«/msubsup»«/math» is 2:1.
This will create a neutral compound.
The ratio of «math»«/math»«math»«msup»«mi mathvariant=¨normal¨»H«/mi»«mo»+«/mo»«/msup»«mo»§#160;«/mo»«mi»to«/mi»«mo»§#160;«/mo»«msubsup»«mi»CO«/mi»«mn»3«/mn»«mrow»«mn»2«/mn»«mo»-«/mo»«/mrow»«/msubsup»«/math» is 2:1.
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/0008hosa3e
Using the rules for naming acids, determine the compound name.
hydroiodic acid = hydrogen iodide
Determine the lowest common multiple of the two ions.
The lowest common multiple between 1 and 1 is 1.
Watch this video to see a teacher work through this example. https://adlc.wistia.com/medias/1bbj6hmocw
Read This
Please read pages 64 and 65 in your Science 10 textbook. Make sure you take notes on your readings to study from later. You should focus on writing formulas and naming acidic
compounds. Remember, if you have any questions or you do not understand something, ask your teacher! Practice Questions
Complete the following practice questions to check your understanding of the concept you just learned. Make sure you write complete answers to the practice
questions in your notes. After you have checked your answers, make corrections to your responses (where necessary) to study from.- Fill in the missing information in this chart.
Acid-Forming Compound Name of Acid-Forming Compound Classical Acid Name HBr HClO nitric acid hydrosulfuric acid
Acid-Forming Compound Name of Acid-Forming Compound Classical Acid Name HBr hydrogen bromide hydrobromic acid HClO hydrogen hypochlorite hypochlorous acid HNO3 hydrogen nitrate nitric acid H2S hydrogen sulfide hydrosulfuric acid