AP Chemistry : Naming Compounds

Study concepts, example questions & explanations for AP Chemistry

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Example Questions

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Example Question #1 : Naming Compounds

What is the IUPAC name for CH_3CH_2CH_2OH?

Possible Answers:

Propene

Propenol

Ethanol

Propanol

Propane

Correct answer:

Propanol

Explanation:

CH_3CH_2CH_2OH is a saturated hydrocarbon with an organic functional group, -OH, or alcohol.

CH_3CH_2CH_3 is propane, so we will remove the "e" from the end of that name and add the suffix "ol" to denotate an alcohol, so the correct answer is propanol.

Propenol is propanol with a double bond in the hydrocarbon chain. Ethanol is a saturated two-carbon chain with an alcohol functional group.

 

Example Question #2 : Naming Compounds

Name the following compound: .

Possible Answers:

Nitrogen(IV) tetraoxide

Nitride oxide

Dinitrogen quadoxide

Dinitrogen tetraoxide

Correct answer:

Dinitrogen tetraoxide

Explanation:

Covalent non-metal/non-metal compounds are named by taking the name of each element and appending the apropriate greek prefix to indicate the number of each atom present—in this case, di- for two and tetra- for four. The end of the more electronegative element is substituted with "ide". This gives the name of dinitrogen tetraoxide.

Example Question #3 : Naming Compounds

What is the systematic name for ?

Possible Answers:

Cesium sulfur tetraoxide

Cesium (I) sulfate

Cesium sulfite

Cesium sulfate

Correct answer:

Cesium sulfate

Explanation:

Ionic compounds are named by naming the cation followed by the anion. Since the cation, cesium, is an alkali metal the oxidation state, should not be specified. Alkali metals will always have an oxidation state of 1. The anion, , is sulfate. Together, the full name of the compound is cesium sulfate.

Example Question #4 : Naming Compounds

Name the following compound: 

Possible Answers:

Zinc perchlorate

Zinc chloride tetroxide 

Zinc dichlorate

Zinc chlorate

Zinc chloride

Correct answer:

Zinc perchlorate

Explanation:

The compound's name is zinc perchlorate. With the addition of a fourth oxygen atom to the molecule, chlorate , we follow the polyatomic ion naming rules and add a per- to the molecule's name, giving us perchlorate. When bonded ionically to a zinc cation , the resulting ionic compound is called zinc perchlorate.

Example Question #5 : Naming Compounds

What is the formula of hydroiodic acid?

Possible Answers:

Correct answer:

Explanation:

 is the correct formula because, following IUPAC acid naming rules, when combining a hydrogen cation with an anion that consists of only one element (in this case iodide), one drops the -ide ending, adds an -ic ending and adds a hydro- prefix. Other examples would be hydrochloric acid  and hydrofluoric acid .

Example Question #6 : Naming Compounds

A student named a certain organic molecule 2-(1-methylbutyl)-3-isopropylbutane. While this name may give the possibility of correctly drawing the molecule, it does not follow correct IUPAC naming guidelines. What is the correct name of this molecule?

Possible Answers:

3-(2-pentyl)-2-isopropylbutane

2-(2-pentyl)-3-isopropylbutane

3,4-dimethyl-2-isopropylheptane

2-pentyl-3-propylbutane

2,3,4,5-tetramethyloctane

Correct answer:

2,3,4,5-tetramethyloctane

Explanation:

While the student's description of the location and size of the sidechains is correct, he/she failed to recognize the longest parent chain, it being the eight-carbon string which encompasses what he/she named isopropyl- and pentyl-. The resulting octane molecule has four methyl- substituents at the 2, 3, 4, and 5 positions. 

Example Question #7 : Naming Compounds

Which of the molecules above does not match its molecular formula?

Possible Answers:

Pentane

Isobutane

Decane

Nonane

Butane

Correct answer:

Butane

Explanation:

While it is tempting to think that butane and isobutane, because of their structural differences would have different numbers of of hydrogens, they are in fact constitutional isomers, and have the same molecular formula. Both butane and isobutane have four carbons and ten hydrogens, although butane's carbons and hydrogen's are arranged

 and isobutane's are arranged 

A good rule of thumb for the formulas of simple hydrocarbons is:

Example Question #8 : Naming Compounds

Which of the following is a correct name for the compound, ?

I: Potassium bicarbonate

II: Potassium percabonate

III: Potassium hydrogen carbonate

Possible Answers:

I and III

II and III

II only

III only

I only

Correct answer:

I and III

Explanation:

Because the ion,  , is correctly referred to as both bicarbonate and hydrogen carbonate, the correct names for the compound in question are both potassium bicarbonate and potassium hydrogen carbonate.

Example Question #9 : Naming Compounds

Which of these is not the IUPAC name for the indicated molecule?

Possible Answers:

Hydrofluoric acid; 

Acetic acid; 

Carbonous acid; 

Sulfuric acid; 

Perchlorous acid; 

Correct answer:

Perchlorous acid; 

Explanation:

Because the polyatomic ion from which the acid, , is derived is perchlorate, , the resulting acid is named perchloric acid. The naming protocol is to use the -ic suffix for acids derived from polyatomic ions ending in -ate, while using the -ous suffix for acids derived from polyatomic ions ending in -ite.

Example Question #81 : Compounds And Molecules

What is the name of the compound with the chemical formula ?

Possible Answers:

Dinitrogen monoxide

Nitrate

Pernitrate

Hyponitrite

Nitrite

Correct answer:

Dinitrogen monoxide

Explanation:

All of the incorrect options have prefixes or suffixes associated with polyatomic ions "hypo," "per," "ite," and "ate". Since  is not an ion (it does not have a charge), it must just be a covalent compound. Therefore, use the prefixes reserved for covalent compounds to name it.

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