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Questions and Answers
What is the expected observation when ketones are tested with Fehling's solution?
What is the expected observation when ketones are tested with Fehling's solution?
What is the first step in the Tollen's reagent procedure?
What is the first step in the Tollen's reagent procedure?
What gas is produced when magnesium is tested in a solution, as observed?
What gas is produced when magnesium is tested in a solution, as observed?
When anhydrous sodium carbonate is added to a test tube, which of the following observations is expected?
When anhydrous sodium carbonate is added to a test tube, which of the following observations is expected?
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Which is NOT a step in the mass spectrometry process?
Which is NOT a step in the mass spectrometry process?
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What occurs during the ionisation stage of mass spectrometry?
What occurs during the ionisation stage of mass spectrometry?
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What is formed as a result of the polymerisation reaction of chloroethene?
What is formed as a result of the polymerisation reaction of chloroethene?
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Which breakdown product is associated with the thermal cracking of 1,2-dichloroethane?
Which breakdown product is associated with the thermal cracking of 1,2-dichloroethane?
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What must occur for ethane to be formed in a chain reaction involving chloromethane?
What must occur for ethane to be formed in a chain reaction involving chloromethane?
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Which substance acts as a catalyst in the esterification process mentioned?
Which substance acts as a catalyst in the esterification process mentioned?
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In an addition reaction, what is a key characteristic of the bonds involved?
In an addition reaction, what is a key characteristic of the bonds involved?
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What is the primary outcome when the C=C double bond in ethene is polarized by Br2?
What is the primary outcome when the C=C double bond in ethene is polarized by Br2?
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What happens to the geometry of the molecules during an addition reaction on a double or triple bond?
What happens to the geometry of the molecules during an addition reaction on a double or triple bond?
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Which of the following statements about free radicals in the reaction is true?
Which of the following statements about free radicals in the reaction is true?
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What is the role of the brine in the soap preparation process?
What is the role of the brine in the soap preparation process?
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What is the primary function of anti-bumping granules in the soap preparation process?
What is the primary function of anti-bumping granules in the soap preparation process?
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What determines whether particles pass through the spectrometer to the detector?
What determines whether particles pass through the spectrometer to the detector?
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What does the height of a peak in a mass spectrum indicate?
What does the height of a peak in a mass spectrum indicate?
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Which factor influences the separation in paper chromatography?
Which factor influences the separation in paper chromatography?
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In gas chromatography, what does the gaseous mobile phase carry?
In gas chromatography, what does the gaseous mobile phase carry?
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What is the stationary phase in column chromatography?
What is the stationary phase in column chromatography?
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Which application is NOT typically associated with mass spectrometry?
Which application is NOT typically associated with mass spectrometry?
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What happens during the elution process in column chromatography?
What happens during the elution process in column chromatography?
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In paper chromatography, where should the spot of the sample mixture be placed?
In paper chromatography, where should the spot of the sample mixture be placed?
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What type of reaction produces ethene from ethanol?
What type of reaction produces ethene from ethanol?
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Which of the following statements is true regarding polymerization?
Which of the following statements is true regarding polymerization?
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When a primary alcohol is oxidized, it is converted to which compound?
When a primary alcohol is oxidized, it is converted to which compound?
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What is formed when a secondary alcohol reacts with acidified sodium dichromate?
What is formed when a secondary alcohol reacts with acidified sodium dichromate?
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What is the primary product formed when ethene undergoes the addition of bromine in the presence of chlorine ions?
What is the primary product formed when ethene undergoes the addition of bromine in the presence of chlorine ions?
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Which reagent is used in the mandatory experiment to oxidize ethanal?
Which reagent is used in the mandatory experiment to oxidize ethanal?
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What is the purpose of adding dilute sulfuric acid in the experiment with ethanal and potassium manganate(VII)?
What is the purpose of adding dilute sulfuric acid in the experiment with ethanal and potassium manganate(VII)?
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In the oxidation experiment using Fehling's solution, what is the initial color of the solution?
In the oxidation experiment using Fehling's solution, what is the initial color of the solution?
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What is the role of the mobile phase in gas chromatography?
What is the role of the mobile phase in gas chromatography?
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How does high-performance liquid chromatography (HPLC) achieve effective separation of components?
How does high-performance liquid chromatography (HPLC) achieve effective separation of components?
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What type of information can ultraviolet (UV) spectroscopy provide that infrared (IR) spectroscopy cannot?
What type of information can ultraviolet (UV) spectroscopy provide that infrared (IR) spectroscopy cannot?
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In what application is gas chromatography frequently used?
In what application is gas chromatography frequently used?
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Which bonded structure would absorb infrared radiation at a different frequency than C=O in IR spectroscopy?
Which bonded structure would absorb infrared radiation at a different frequency than C=O in IR spectroscopy?
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What is one of the main uses of infrared (IR) spectroscopy?
What is one of the main uses of infrared (IR) spectroscopy?
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What does the coiled column in gas chromatography primarily serve as?
What does the coiled column in gas chromatography primarily serve as?
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During the mandatory experiment of separating ink components using paper chromatography, how is the mobile phase initially prepared?
During the mandatory experiment of separating ink components using paper chromatography, how is the mobile phase initially prepared?
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What is the primary purpose of refluxing during the preparation of soap?
What is the primary purpose of refluxing during the preparation of soap?
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What type of reaction occurs in Stage 1 of soap preparation?
What type of reaction occurs in Stage 1 of soap preparation?
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Which substance is removed during the distillation in Stage 2?
Which substance is removed during the distillation in Stage 2?
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What is the function of the brine in Stage 3 of the soap preparation?
What is the function of the brine in Stage 3 of the soap preparation?
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Why is it important to wash the soap thoroughly in Stage 4?
Why is it important to wash the soap thoroughly in Stage 4?
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What co-product is formed during the soap preparation process?
What co-product is formed during the soap preparation process?
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How does sodium stearate interact with oils and salts in sweat?
How does sodium stearate interact with oils and salts in sweat?
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What is the maximum possible yield of soap from 4.45 g of glyceryl tristearate?
What is the maximum possible yield of soap from 4.45 g of glyceryl tristearate?
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Study Notes
Substitution Reactions
- A substitution reaction is a chemical reaction where an atom or group of atoms in a molecule is replaced by another atom or group.
- Alkanes undergo substitution reactions with halogens in the presence of ultraviolet light.
- Example: CH4 + Cl2 → CH3Cl + HCl (methane reacts with chlorine to form chloromethane and hydrogen chloride).
Halogenation of Alkanes
- Halogenation is a type of substitution reaction.
- Halogen atoms replace hydrogen atoms in an alkane molecule.
- Continued halogenation can lead to the formation of di-, tri-, or tetrachloromethanes.
Mechanism of Monochlorination of Methane
- The mechanism of a reaction is a step-by-step description of how the overall reaction proceeds.
- The mechanism of monochlorination of methane is a free-radical substitution mechanism.
Initiation
- A chlorine molecule is broken down into two chlorine atoms in the presence of ultraviolet light.
- This creates chlorine free radicals.
Propagation
- A chlorine free radical attacks a methane molecule, forming hydrogen chloride and a methyl free radical.
- The methyl free radical attacks another chlorine molecule, forming chloromethane and a chlorine free radical.
Termination
- When most reactants are used up, remaining chlorine and methyl radicals combine to form Cl2, chloromethane, and ethane, ending the chain reaction.
Evidence for the Mechanism
- Reaction occurs when exposed to UV light.
- Thousands of chloromethane molecules are formed for every photon of light absorbed.
- Ethane is a product of the reaction.
- Free radicals speed up the reaction.
Addition Reactions
- An addition reaction is a reaction where two or more molecules combine to form a single molecule.
- Addition reactions always occur at double or triple bonds.
- The geometry of the molecule changes from planar to tetrahedral bonds.
- Examples include hydrogenation of vegetable oils and the formation of plastics.
Polarisation
- The C=C double bond in ethane has a high concentration of negative charge.
- As Br2 approaches ethane, electrons are repelled, polarising the Br2 molecule.
Heterolytic Fission
- The Br2 molecule splits into Br⁺ and Br⁻ ions.
Carbonium Ion Formation
- The Br⁺ ion attacks the electron-rich C=C double bond.
- This forms a carbonium ion.
Ionic Addition
- The carbonium ion is attacked by the Br⁻ ion.
- This results in the formation of 1,2-dibromethane.
Polymerisation Reactions
- Polymers are long chain molecules made by joining together many small molecules.
- Polymers are repeating structures consisting of thousands of monomers linked together.
- Polyvinyl chloride (PVC) is a common plastic.
- The repeating unit of a polymer is the part whose repetition forms the complete polymer chain, excluding end groups.
Elimination Reactions
- An elimination reaction is a reaction where a small molecule is removed from a larger molecule, often producing a double bond in the larger molecule.
Redox Reactions
- When a primary alcohol reacts with an oxidizing agent, the primary alcohol is converted into an aldehyde.
- Two hydrogen atoms are removed from the primary alcohol.
- If a secondary alcohol reacts with acidified sodium dichromate, a ketone is formed.
- Aldehydes and ketones can be reduced back to alcohols using hydrogen and a nickel catalyst.
Mandatory Experiment: To Prepare Soap
- Detailed procedures are outlined (using 2.5g of lard, 2.5g KOH, and 20cm³ ethanol, in a reflux apparatus using a water bath, then distillation, dissolution in water, and precipitation in brine followed by filtration).
- Testing the soap is also outlined.
Mandatory Experiment: To Study Reactions of Ethanal
- Experiments on ethanal using acidified potassium permanganate, Fehling's reagent, and ammoniacal silver titrate are described.
- Observations and analysis are discussed for each step.
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Description
Explore the intricacies of substitution reactions, specifically focusing on the halogenation of alkanes. This quiz delves into mechanisms, examples, and processes involved in the reaction of alkanes with halogens under ultraviolet light. Test your understanding of these essential chemical concepts!
