Correct Answer: (3) C
5
H
8
Why: Carbon is a tetravalent chemical element, which means it has four sets of electrons in its valence (outermost) orbital capable of forming covalent bonds. When carbon is saturated with hydrogen it forms a class of compound known as alkanes with the general formula C n
H
2n+2, the most basic of which is the compound methane CH
4
.
Alkenes are organic chemical compounds consisting of only carbon and hydrogen atoms (hydrocarbons). What distinguishes it from other hydrocarbons is the fact that their carbon atoms have not been saturated by hydrogen (are unsaturated) resulting in two carbon atoms sharing electrons to form a double bond. As a result alkenes have the formula C n
H
2n
, the most basic of which is the compound ethene C
2
H
4
. If the hydrocarbon is unsaturated and contains a triple bond it is called an alkyne and has the general formula C n
H
2n-2
.
Answering this question: The general formula for (1), (2) and (4) are all the same C n
H
2n+2 representing the class of saturated hydrocarbons known as alkanes. Even if you were not sure what an unsaturated hydrocarbon was, (3) is the only answer with a different general chemical formula. Also, C
5
H
8
is the only compound in the set not saturated with hydrogen; it also corresponds to the general formula for alkynes C n
H
2n-2
.
Correct Answer: (2) Propene
Why: IUPAC stands for the International Union of Pure and Applied Chemistry, and they have established a set nomenclature and symbols for chemical elements and compounds. Looking at the structural formula of this compound it can be noticed that the distinguishing characteristic of the compound is its double bond. The correct nomenclature for a double bond is the suffix ene. Therefore Propene is the correct answer.
The suffix -ane is the standard single bonded saturated hydrocarbon. The suffix -anone is for hydrocarbons that contain an oxygen, and the suffix -anal is for a hydrocarbon that contains a double bonded OH molecule.
Answering this question: Having some organic chemistry experience can hopefully help you eliminate answer (1) just by recognizing that -ane is for simply hydrocarbon and this hydrocarbon clearly has a distinguishing characteristic. Beyond this it is mostly necessary to understand the different suffixes and determine the correct one. The simplest way to remember that -ene means double bonds is to remember alkenes are hydrocarbons with double bonds.
Correct Answer: (4) structural formulas
Why: Isomers are two or more chemically identical substances but have a different arrangement of the atoms. Because they are composed of the same type of elements and same number of elements their formula masses will always be the same. Molecular formulas simply state what elements are present and in what proportion to each other and since this does not change from isomer to isomer it will also be the same. The empirical formula expresses the relative numbers of each type of atom by reducing it two the simplest whole number ratio of the elements present. Again the relation and ratio of the elements in isomers does not change so the empirical formula will also not change. Lastly the structural formula is the only possible answer that describes the arrangement of the atoms in the compound and that by definition is what isomers have different. Therefore (4) is the only possible correct answer.
Answering this question: Even if you can't remember the differences between the molecular and empirical formulas this question is solvable. Simply remember that isomers have different structures and immediately answer (4) stands out for you. There is only one possible correct answer so if you can determine one to be correct it is not necessary to know or eliminate any of the other answers.
Correct answer: (2) ether
An organic acid refers to a chemical compound containing a carboxyl functional group (COOH). The presence of the said compound is expected for foods that contain carbon. It is denoted by the general structural formula:
An ester is an organic compound formed from the reaction of an organic acid and an alcohol. The said reaction is classified as a condensation reaction or esterification process. An ester is denoted by the general structural formula:

An aldehyde is an organic chemical formed from oxidation of alcohols and contains a functional group CHO. This compound is commonly used in manufacturing dyes, resins and organic acids. It is denoted by the general structural formula:
An ether is an organic compound with a distinct structure of having an oxygen atom serve as link a for two hydrocarbon groups. It can be utilized in manufacturing medicines. It is denoted by the general structural formula:
Answering the question: Looking at the structural formula, 2 groups of C 2 H 5 are linked by a single oxygen atom. C 2 H 5 are both hydrocarbon groups. Therefore, the given formula represents an ether which is option no. 2. Options no. 1, 3 and 4 are easily eliminated.
reaction .
Correct Answer: The reaction type is an organic addition
Why: Organic compounds are large range of carbon containing compounds. In the above equation C
4
H
8
is an organic compound belonging to the group known as alkenes. Alkenes have the general formula C n
H
2n
and contain a pair of carbon atoms covalently double bonded to each other. This double bond is what makes it possible for organic compounds to carry out addition reactions.
Answering the question: In order to answer this question you will need to have memorized the different chemical reaction types. In this case Cl 2 is being added to butene to form di-chloro butane. It should also be noted the organic compounds most commonly involved in addition type reactions are the alkenes and alkynes as they have carbon to carbon double and triple bonds respectively.
Correct answer: CH
2
(Cl)-CH (Cl)-CH
2
-CH
3
Answering the question: In order to answer the question an understanding of the International Union of Pure and Applied Chemists
(IUPAC) naming convention is helpful.
1) Identify the parent hydrocarbon chain
2) Identify the functional group
3) Identify any side chains
4) Identify the remaining functional groups
To draw the structural formula, start by identifying the parent hydrocarbon chain, which is the longest straight chain present in the compound. According to IUPAC naming convention that would be butane (1,2-dichloro butane ).
C-C-C-C
Butane is a saturated hydrocarbon containing 4 carbon atoms. That means it does not contain any double or triple bonds.
The next step is to interpret the remainder of the name 1,2-dichloro butane. This part of the name is telling us the name of the additional elements found in the molecule and their location.
C
1
-C
2
-C
3
-C
4
The first two carbons in the chain would be carbon 1 and 2 respectively, while the dichloro tells us that there are two chloride atoms present. Therefore 1,2-dichloro tells us the location and number of the chloride atoms present on the molecule. Below is one possible configuration for 1,2-dichlorobutane

Answer: (1)
Why?
Organic chemistry (or carbon chemistry) by definition is the study of carbon-based compounds, carbon and hydrogen compounds (hydrocarbons) and other derivatives of carbon and hydrocarbons. Organic compounds may contain other elements such as chlorine, nitrogen and oxygen, but these only help to form functional groups associated with carbon compounds.
Answering the Question:
To answer the question, it is important to know what defines an organic compound. Organic compounds are defined by the presence of carbon in there chemical structure. This class of compound is very well known, as many of them are present in living systems on earth.
This leaves (1) as the only possible answer.
Answer: butyne
Why?
Organic chemistry is an extremely diverse field of chemistry focusing on carbon chemistry or carbon related molecules and there reactions. The types of elements bonded to a carbon atom and the type of bonds shared, will determine the properties of the molecule and hence the category that molecule will assigned.
A carbon ≡ carbon triple bond is representative of a group of organic compounds called alkynes. All hydrocarbon members of this functional group have the suffix yne in their name. The prefix of the name is dependent on the total number of carbon atoms in the molecule and the type and position in the main carbon chain, and any side groups of hydrocarbons. For example, if the carbon compound has a carbon-to-carbon triple bond and is composed of only two (2) carbon atoms, it will have a prefix of eth denoting two (2) carbon atoms and a suffix of yne , denoting the functional group of the molecule. The final name of the compound would be ethyne .
There are three (3) main groups of hydrocarbons, based on the number of carbon-to-carbon bonds present in the molecule. If the hydrocarbons consist of only carbon - carbon single bonds, then they are categorized as alkanes. However, if there is a carbon = carbon double bond present in the hydrocarbon, it is categorized as an alkene.
Answering the Question: To determine the answer to this question, an understanding of carbon chemistry (organic chemistry) is necessary. In particular it is important to have knowledge of the functional groups present in organic chemistry, then the answers can be analyzed in turn.
(1) Butane is a four-carbon molecule containing only carbon-to-carbon single bonds. The fact that butane only has carbon-to-carbon single bonds can be determined by analyzing the suffix of the compound. Butane is an alkane; this group is in the category of compounds possessing only single bonds.
(2) Butanone belongs to the chemical group known as ketones. This category of organic molecules has a carbon covalently double bonded to oxygen and also two hydrocarbon groups.
(3) Butene is another four-carbon compound, however it differs from butane by having a carbon = carbon double bond.
Based on the functional groups present on the molecules, Answer (4), butyne, is the only possible answer.
Answer: (3)
Why?
An unsaturated hydrocarbon is an organic molecule with at least one carbon to carbon double or triple bond and composed entirely of only carbon and hydrogen atoms (hydrocarbon). Those hydrocarbons, which contain a carbon-to-carbon double bond (C =
C), are called alkenes, while those with carbon-tocarbon triple bonds (C ≡ C) are call alkynes.
Answering the Question: Answer (1) belongs to a group of compounds called aldehydes and contains a carbon to oxygen double bond. This results in answer (1) being incorrect for two reasons; 1) it is not a hydrocarbon, as it contains an oxygen molecule and 2) it would not be considered unsaturated since the double bond is not present between two carbon atoms.
Answer (2) belongs to the group of compounds called alkanes. This group of hydrocarbons contains no carbon-to-carbon double or triple bonds and hence would be considered a saturated hydrocarbon.
Answer (3) is the only hydrocarbon with a carbon-to-carbon double or triple bond. It belongs to the group of compounds known as alkenes, which are characterized by the presence of a carbon-to-carbon double bond. Alkenes meet both the requirements of being a hydrocarbon and being unsaturated.
Answer (4) is typical of the group called ether. They are identified by the carbon-to-oxygen-to-carbon bond within the molecule. This molecule, therefore, does not meet the requirements of the question. It cannot be classified as a hydrocarbon, as it contains an oxygen atom, and it does not contain any carbon-to-carbon double or triple bonds.
Therefore, the best possible answer is answer (3).

Answer: R-NH
2
or R-COOH
Why? Glycine is an organic compound found in proteins and is in fact one of the building blocks of some proteins. Glycine is an amino acid, this means it carries two functional groups; 1) an amine group R-NH
2
and 2) a carboxylic acid group R-COOH, where R is a hydrocarbon group (eg CH
3
CH
2
-). Amino acids have the general structure H
2
N-CH-R-COOH and are essential for life as they are the building blocks for proteins. Amino acids at a certain pH, called the isoelectric point, forms a zwitterion, which has both a positive and negative charge.
+ H3N-CH-R-COO -
Zwitterions have the ability to react as both an acid and a base.
Answering the Question: To answer the question it is necessary to know what group glycine belongs to. However if this is not known, writing out the given general formula will also help. The main carbon chain is composed of carbon and hydrogen only, all other groups attached to the carbon and hydrogen chain can be considered functional groups.
Therefore, NH 2 and COOH are the only possible options in the case of glycine.
(2) Amine is the correct answer. You can locate this on your table of organic roots and you should remember that amines are organic compounds and functional groups that contain a basic nitrogen atom with a lone pair. Amines are derivatives of ammonia.
The molecules of 2-iodo-2-methylpropane are more polar than the molecules in 2-methylpropane.
Also, there are stronger intermolecular forces between the molecules of 2-iodo-2-methylpropane.
Both of these factors cause 2-iodo-2-methylpropane to have a higher boiling point.