Correct Answer: (3) C₅H₈

Why:

Carbon is a tetravalent chemical element, which means it has four sets of electrons in its valent (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_nH_2n+2, the most basic of which is the compound methane CH₄.

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_nH_2n, the most basic of which is the compound ethene C₂H₄.  If the hydrocarbon is unsaturated and contains a triple bond it is called an alkyne and has the general formula C_nH_2n-2.

Answering this question:

The general formula for (1), (2) and (4) are all the same C_nH_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, C₅H₈ is the only compound in the set not saturated with hydrogen; it also corresponds to the general formula for alkynes C_nH_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: (3) CH₃COOH (acetic acid)

Why:

An electrolyte is a substance that contains free ions and conducts electricity.  Generally they are comprised of ions in solution and are often called ionic solutions, though molten or solid electrolytes are also possible.   Of the choices available in this answer (3) is the only acid which by definition breaks apart in water to increase hydrogen ion activity.  Looking at the other possibilities they are all relatively stable and not ionic.  Therefore (3) is the best answer.

Answering this question:

If you can not look at the compounds and recognize them instantaneously, the best way to solve this problem is to compare their structures and determine which will be most likely to break into ions in a solution.  (1) is a relatively stable structure with no Hydrogens to donate.  (2) can be recognized as an alcohol relatively quick and we know this is not a compound that breaks down into ions. (4) can be recognized as an aldehyde with the double bonded Oxygen and also not a common ionic compound.  This only leaves (3) as being suspicious with both the Double bonded  Oxygen and an alcohol group (COOH) This looks like an ionic compound and if recognized as acetic acid you know immediately it is electrolytic.

Correct answer: (2) CH₂O

The empirical formula of a chemical compound is the simplest number ratio of atoms of each element present in a compound.

Answering the question:

Option no. 1 is eliminated because CHO does not refer to glucose, rather, it refers to a carbon-hydrogen-oxygen chain known as Carbohydrate.

Option no. 3 refers to glucose.  However this is eliminated because C₆H₁₂O₆ is a molecular formula of glucose and not an empirical formula.

Option no. 4 is eliminated because C₁₂H₂₄O₁₂ does not show the simplest number ratio of atoms of each element.

Therefore, the empirical formula of glucose is represented by option no. 2, CH₂O.

Correct answer: (3)

A nonpolar covalent bond is defined as the bond in which electrons are shared between elements having a difference in electro negativity of less than 0.5. This means 2 elements will low or equal electro negativity will not pull electrons to one element more than the other. What this mean is that no net charge will be present on one element over another. The halogens in group 7 are the prime example of this.

Answering the Question:

To answer this question it is important to understand that to form a nonpolar covalent bond you should have 2 similar elements so that no one element will pull electrons more towards itself. Br-Br is the only molecule made up of similar elements. Making (3) the correct answer.

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:

Correct Answer:

The reaction type is an organic addition reaction. Organic compounds are large range of carbon containing compounds. In the above equation C₄H₈ is an organic compound belonging to the group known as alkenes. Alkenes have the general formula C_nH_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:

Correct answer:

CH₂(Cl)-CH (Cl)-CH₂-CH₃

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-dichlorobutane).

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-dichlorobutane. This part of the name is telling us the name of the additional elements found in the molecule and their location.

C₁-C₂-C₃-C₄

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

Correct Answer:

As the number of carbon atoms in the hydrocarbon molecules increase, there is a proportional increase in the boiling point of the hydrocarbons contained in the crude oil.

The boiling point of a substance is an approximation of the energy required for a molecule to escape the intermolecular forces of attraction with its closest neighboring molecule. Generally speaking the larger the hydrocarbon molecule the greater the intermolecular forces of attraction. This is as a result of the increase in surface area of a molecule with increasing carbon count. The increased surface area of the molecule leads to greater interaction between that molecule and neighboring molecules, leading to stronger intermolecular forces.

Answering the question:

This question is based on the trends shown in the diagram. A simple way to follow a trend is by drawing a graph of the trend. This allows a visual representation of the information and usually leads to easier interpretation. In the diagram above it can already be observed that the carbon count increases as temperature increases showing the major trend immediately.