CHEM-219- MODULE 2 EXAM|LATEST UPDATE 2024|VERIFIED PORTAGE LEARNING EXAM QUESTIONS AND CORRECT ANSWERS ALL GRADED A+|GUARANTEED SUCCESS

CHEM-219- MODULE 2 EXAM|LATEST UPDATE 2024|VERIFIED PORTAGE LEARNING EXAM QUESTIONS AND CORRECT ANSWERS ALL GRADED A+|GUARANTEED SUCCESS| What are hydrocarbons? - ANSWER-Molecules composed of only the elements carbon and hydrogen What are the two major classes of hydrocarbons? - ANSWER-Aromatic (benzene) and aliphatic (alkanes, alkenes, alkynes) What is the main source of hydrocarbons? - ANSWER-Fossil fuels like coal, petroleum, and natural gas obtained by mining and drilling. What are Alkanes? - ANSWER-They are saturated hydrocarbons because their skeleton is only composed of C-C single bonds. How can alkanes exist? - ANSWER-They can be linear, branched or exist in ring formations called cycloalkanes. Describe a higher/more complex alkane structure: - ANSWER-They will have more carbons and/or increased structural diversity. What is the general formula of Alkanes? - ANSWER-CnH2n+2 The names of the alkanes reflect? - ANSWER-The number of carbons present. How many isomers does each alkane have from 1-10 - ANSWER-1,1,1,2,3,5,9,18,35,75 Name the first ten prefix of alkanes: - ANSWER-Methane, ethane, propane, butane, pentane, hexane, heptane, octane, nonane, decane. As the molecular weight increases: - ANSWER-The number of isomers increase. What does the suffix -ane mean? - ANSWER-Denotes a saturated hydrocarbon. It is used for all acyclic saturated alkanes What is nomenclature? - ANSWER-The naming of a molecular structure. Historically they were named after their source, now they are systemic. Why is nomenclature important? - ANSWER-Because we cannot remember all the prefixes since a MF composed of carbons can have several different patterns of connectivity. What is it meant by the systemic approach? - ANSWER-There are now methods of naming molecules so that they all have unique names. You can then determine the structure from only the name and vice-versa. IUPAC rules for naming branced alkanes: - ANSWER-1. Find the parent name by identifying the longest continuous chain of carbons. 2. Number the parent chain. (begin at the end of the chain nearest to the first branch.) 3. If there are two equally long continuous chains, select the one with most branches. 4. If the first branch point is the same distance, choose the one that gives the lowest substituents. 5. If the substituents are both equidistant then choose the numbering so the substituent goes with the higher alphabetic priority. How are linear alkanes named? - ANSWER-By combining the prefix indicating the number to the suffix -ane. What is a substituent? - ANSWER-Any group attached to the parent chain. What are alkyl groups? - ANSWER-Saturated hydrocarbon substituents. You drop the -yl for -ane. A one carbon substituent is a methyl group, four carbon is butyl. What is a locant? - ANSWER-A number used to determine the suffix. Describes the position of substituents. What happens when two or more of the same type of substituents are present on the parent chain? Like 3 methyl groups - ANSWER-Additional prefixes including the number are added. How would you describe finding 2,3 dimethylpentane? - ANSWER-It is a 5 carbon chain, then it has substituents on numbers 2, 3 and those are methyl groups. How are IUPAC systematic names put together? - ANSWER-Locant-(prefix) substituentparent If two or more different substituents are present on the parent chain then what happens? - ANSWER-They are listed alphabetically. Ethyl before methyl How are halogen atoms as substituents named? - ANSWER-Change the -ine to -o, chlorine=chloro, bromine=bromo. propyl or n-propyl - ANSWER-CH3CH2CH2 isopropyl - ANSWER-CH3CHCH3 What does the squiggle bond mean? - ANSWER-Point of attachment to the parent chain. Butyl or n-butyl - ANSWER--CH2CH2CH2CH3 sec-butyl - ANSWER-CH3CHCH2CH3 isobutyl - ANSWER- tert-butyl - ANSWER- Isobutyl would be alphabetized as? While sec-butyl would be alphabetized as? - ANSWER-I, B What does R represent? - ANSWER-It is a generic/wildcard notation in organic structure. Any alkyl group. This is known as R-group notation. Why is R chosen? - ANSWER-It is not on the chart anywhere. What is the important thing to know about the physical properties of alkanes. - ANSWER-They will show similar trends in terms of their physical properties. What does the physical properties of a molecule refer to? - ANSWER-Characteristics like melting point, boiling point, density, solubility. How do you compare the boiling point of alkanes? - ANSWER-The longer the length of carbon, the higher the Boiling point. When it is branched, it can have a higher boiling point, as long as it isn't the parent chain that is branched. Are alkanes soluble in water? - ANSWER-They are water-insoluble. Are alkanes polar or non-polar? - ANSWER-Almost non-polar What is hydrogen bonding? - ANSWER-The water molecules are attracted to each other like magnets because of it's electron rich O atom possessing a -charge and its electron poor H possessing a + charge What will a mixture of alkane and water make? - ANSWER-A two layer-biphasic system. It will float on top of water. since its density is less than 1g/ml Are liquid alkanes used as solvents? - ANSWER-Yes for other non polar substances. When compared to other polar molecules of similar weight, are alkanes lower or higher in melting and boiling points? - ANSWER-They are lower. What are Van der Waals forces? - ANSWER-The attractive forces between molecules. The polarization in VDWF's are: - ANSWER-Temporary and weak What is the relationship between branching and VDWF? - ANSWER-As you branch out you gain more surface area and lower the VDWF. Which lowers the BP and MP Alkanes can adopt different conformations, What does this mean? - ANSWER-This means that it can change shapes as it can rotate around bonds. Hydrogen bonding and VDWFS are classifies as nonbonding intermolecular forces, what does this mean? - ANSWER-That they are attractive forces between molecules that are not true bonds in the sense of sharing or donating. What are conformers? - ANSWER-Different shapes of molecules that are derived by rotations of single bonds. What does the Newman projection do? - ANSWER-It shows the conformation of molecules when looking down a particular bond axis. What is the difference in hydrogen placement between an eclipsed confirmation and a staggered one? - ANSWER-The hydrogens do not overlap in staggered but they do in eclipsed. Certain conformers are called rotamers, why? - ANSWER-They can simply be rotated into the other conformer. Used with newman projections Staggered vs. Eclipsed Conformers - ANSWER-Staggered are generally more stable, because of the removed repulsion that occurs when electrons are aligned on top of each other in an eclipsed. How do you name newman projections? - ANSWER-Find the first carbon chain, attach it to the front carbon. The rest are substituents. Then attach it to the back carbon. Then attach the first carbon chain, the rest are substituents. Can conformers be isolated at room temp? - ANSWER-No, because theres a lot of thermal energy, it starts the rapid inter conversion of conformers. Meaning it rotates back and forth