Organic Chemistry Quiz: Hydrocarbons

Ethene is the correct answer because it is the only molecule listed that contains a carbon-carbon double bond. Ethane, ethyne, and ethyl alcohol do not have a carbon-carbon double bond. Ethene, also known as ethylene, is a hydrocarbon with the chemical formula C2H4 and consists of two carbon atoms bonded together by a double bond.

Dehydration refers to the removal of water from a substance. In this context, the correct answer is "Water" because dehydration specifically involves the elimination or loss of water molecules.

Chloromethane, also known as methyl chloride, is reduced to produce methane. Reduction is a chemical reaction in which a molecule gains electrons or hydrogen atoms, resulting in a decrease in oxidation state. In this case, chloromethane gains hydrogen atoms to form methane, which is the product of the reduction reaction.

Hydrogenation is the process that produces an alkane. This process involves the addition of hydrogen gas (H2) to an unsaturated hydrocarbon, such as an alkene or alkyne, resulting in the formation of a saturated hydrocarbon, which is an alkane. During hydrogenation, the double or triple bond in the unsaturated hydrocarbon is broken, and hydrogen atoms are added to the carbon atoms, resulting in the formation of single bonds. This process is commonly used in the food industry to convert unsaturated vegetable oils into solid fats, such as margarine, by adding hydrogen to the double bonds present in the oils.

Fluorine (F2) reacts explosively with methane due to its high reactivity and strong oxidizing properties. Fluorine is the most electronegative element, and it readily accepts electrons from other elements, including carbon in methane. This reaction releases a large amount of energy, resulting in an explosive reaction. Chlorine (Cl2), bromine (Br2), and iodine (I2) are also halogens but are less reactive than fluorine and do not react explosively with methane.

C2H6, also known as ethane, does not react with aqueous solution of bromine. Ethane is a saturated hydrocarbon with only single bonds between carbon atoms. Bromine, being a halogen, typically reacts with unsaturated hydrocarbons that have double or triple bonds, such as C2H4 (ethylene) and C2H2 (acetylene). Since ethane does not have any double or triple bonds, it does not undergo a reaction with bromine in an aqueous solution.

Bromine water can be used to differentiate between ethane and ethyne because ethyne is an unsaturated hydrocarbon and will react with bromine water, causing it to decolorize. Ethane, on the other hand, is a saturated hydrocarbon and will not react with bromine water, so the solution will retain its original color. Therefore, the observation of decolorization of bromine water can be used to identify ethyne.

Zinc (Zn) reacts with hydrochloric acid (HCl) to form zinc chloride (ZnCl2) and hydrogen gas (H2). This reaction is commonly used in the laboratory to generate hydrogen gas. The reaction between Zn and HCl is a redox reaction, where zinc is oxidized to zinc ions (Zn2+) and hydrogen ions (H+) are reduced to form hydrogen gas. The reaction occurs at room temperature and does not require any catalyst.

Alcoholic KOH is used for dehydrohalogenation. Dehydrohalogenation is a chemical reaction in which a hydrogen halide is eliminated from a molecule, resulting in the formation of a double bond. Alcoholic KOH, or potassium hydroxide dissolved in alcohol, is a strong base that can abstract a hydrogen atom from a molecule, leading to the elimination of a halogen atom and the formation of a double bond. This reaction is commonly used in organic chemistry to synthesize alkenes from alkyl halides.

Ethyne (also known as acetylene) reacts with KMnO4 to produce oxalic acid. This reaction is a typical example of an oxidative cleavage reaction. Ethyne is a highly reactive compound due to the presence of a triple bond between carbon atoms. When ethyne reacts with KMnO4, the triple bond is broken, and two carboxylic acid groups are formed, resulting in the production of oxalic acid. This reaction is commonly used in organic chemistry for the synthesis of oxalic acid.