Podcast
Questions and Answers
What is the correct formula for calculating concentration using the number of moles?
What is the correct formula for calculating concentration using the number of moles?
- c = n × V
- c = n / V (correct)
- c = V / n
- c = n + V
When calculating the concentration of an unknown substance, which variable represents the volume in the concentration formula?
When calculating the concentration of an unknown substance, which variable represents the volume in the concentration formula?
- m
- n
- c
- V (correct)
In the reaction between dichromate and iron (II) ions, how many moles of Fe2+ ions react with one mole of dichromate ions?
In the reaction between dichromate and iron (II) ions, how many moles of Fe2+ ions react with one mole of dichromate ions?
- 3
- 6 (correct)
- 1
- 14
If a sample contains 12.0% (w/v) dichromate, what does this mean in terms of grams of dichromate per 100 mL of solution?
If a sample contains 12.0% (w/v) dichromate, what does this mean in terms of grams of dichromate per 100 mL of solution?
After using a 32.0 mL sample of dichromate in the reaction, what is the next step to find the concentration of iron (II)?
After using a 32.0 mL sample of dichromate in the reaction, what is the next step to find the concentration of iron (II)?
What will happen to a polar object in a non-polar stationary phase?
What will happen to a polar object in a non-polar stationary phase?
In high performance liquid chromatography (HPLC), which of the following is true about the solvent used?
In high performance liquid chromatography (HPLC), which of the following is true about the solvent used?
How does the attraction to the stationary phase affect the rate of travel of an object?
How does the attraction to the stationary phase affect the rate of travel of an object?
What is the main advantage of using high performance liquid chromatography over traditional column chromatography?
What is the main advantage of using high performance liquid chromatography over traditional column chromatography?
If component A has the shortest retention time in a non-polar solvent system, what can be inferred about its nature?
If component A has the shortest retention time in a non-polar solvent system, what can be inferred about its nature?
Why would an object be desorbed from the stationary phase?
Why would an object be desorbed from the stationary phase?
What does a longer retention time indicate regarding an object's interaction with the stationary phase?
What does a longer retention time indicate regarding an object's interaction with the stationary phase?
During the process of adsorption, what factor primarily determines the speed at which an object travels through a chromatography column?
During the process of adsorption, what factor primarily determines the speed at which an object travels through a chromatography column?
What does the term 'aliquot' refer to in the context of chemical analysis?
What does the term 'aliquot' refer to in the context of chemical analysis?
How is the number of moles of a primary standard calculated?
How is the number of moles of a primary standard calculated?
In a titration setup, where is the 'titre' located?
In a titration setup, where is the 'titre' located?
What is the correct formula for calculating concentration?
What is the correct formula for calculating concentration?
Which of the following is a key strategy for solving volumetric analysis problems?
Which of the following is a key strategy for solving volumetric analysis problems?
What observable effect indicates that an esterification reaction has occurred when adding an alcohol?
What observable effect indicates that an esterification reaction has occurred when adding an alcohol?
What is produced when ethanoic acid reacts with sodium carbonate?
What is produced when ethanoic acid reacts with sodium carbonate?
If no bubbles are observed when adding sodium hydrogen carbonate to a substance, what can be inferred about the substance?
If no bubbles are observed when adding sodium hydrogen carbonate to a substance, what can be inferred about the substance?
Which of the following tests is used to check for the presence of a hydroxyl group in alcohols?
Which of the following tests is used to check for the presence of a hydroxyl group in alcohols?
When adding an acid to test for the carboxyl group, what happens that indicates a positive reaction?
When adding an acid to test for the carboxyl group, what happens that indicates a positive reaction?
Which reagent can be used to produce a fruity smell indicative of an ester?
Which reagent can be used to produce a fruity smell indicative of an ester?
What does the formation of bubbles when testing a substance with sodium carbonate suggest?
What does the formation of bubbles when testing a substance with sodium carbonate suggest?
What type of functional group must be present for the esterification reaction involving alcohols?
What type of functional group must be present for the esterification reaction involving alcohols?
How does the purity of a substance affect its melting point behavior?
How does the purity of a substance affect its melting point behavior?
In the context of testing for alcohol, which reagent is appropriate in the Hydroxyl Group Test?
In the context of testing for alcohol, which reagent is appropriate in the Hydroxyl Group Test?
What is the mean titre calculated from the given titres?
What is the mean titre calculated from the given titres?
How many concordant titres were identified from the data provided?
How many concordant titres were identified from the data provided?
Using the mean titre, what is the expression for the number of moles of potassium dichromate used?
Using the mean titre, what is the expression for the number of moles of potassium dichromate used?
What is the result of the calculation for moles of potassium dichromate used, given the mean titre?
What is the result of the calculation for moles of potassium dichromate used, given the mean titre?
Which of the following correctly defines the concentration of a solution?
Which of the following correctly defines the concentration of a solution?
If the concentration of potassium dichromate is 1.62 × 10^{-3} mol/100 mL, what is this concentration in mol/L?
If the concentration of potassium dichromate is 1.62 × 10^{-3} mol/100 mL, what is this concentration in mol/L?
Which volume was not recognized as a concordant titre?
Which volume was not recognized as a concordant titre?
Why is identifying concordant titres important in titration?
Why is identifying concordant titres important in titration?
Study Notes
Alcohol and Carboxylic Acids
- An indication of an esterification reaction: addition of alcohol results in the formation of fruity-smelling esters.
- Ethanoic acid (CH₃COOH) reacts with sodium carbonate to produce sodium ethanoate, carbon dioxide, and water.
- Reaction: 2CH₃COOH(aq) + Na₂CO₃(s) → (CH₃COO)₂Na(aq) + CO₂(g) + H₂O(l).
- Ethanoic acid also reacts with sodium hydrogen carbonate, yielding sodium ethanoate, carbon dioxide, and water.
- Reaction: CH₃COOH(aq) + NaHCO₃(s) → CH₃COONa(aq) + CO₂(g) + H₂O(l).
- Observations indicate an acid presence if bubbles of CO₂ form; lack of bubbles suggests it is not an acid.
Chemical Tests for Functional Groups
- Tests for double bonds (C=C): Bromine/Iodine test, adding H⁺ (aq)/MnO₄⁻ (aq) or H⁺ (aq)/Cr₂O₇²⁻ (aq) reacts with primary or secondary alcohols.
- Hydroxyl Group: Addition of a reagent forms a smelly ester to confirm the presence of an alcohol.
- Carboxyl Group: Adding a carbonate reagent leads to the evolution of bubbles, indicating acidic properties.
Purity Analysis & Concentration
- A pure substance melts at a consistent temperature; impurities lead to varied melting points.
- In chromatography, the interaction depends on polarity: non-polar substances move slower on polar stationary phases.
- High-Performance Liquid Chromatography (HPLC) enhances efficiency with high pressures in separating components from mixtures.
Stoichiometric Calculations
- Concentration (c) is calculated as n/V, where n is moles and V is volume.
- A non-polar solvent in HPLC separates components based on their retention times.
- When calculating the concentration of dichromate involving multiple components, foundational concentration formulas are applied:
- n = m/M (for moles from mass).
- c = n/V (for concentration).
Titration
- In titration procedures, titre refers to the solution in the burette, and aliquot refers to the sample in the flask.
- To find the mean titre, calculate the average from concordant titres.
- Moles of potassium dichromate are derived from concentration and volume.
- Final concentration calculations can apply to specific body analyses, such as ethanol concentration expressed in mol/100 mL.
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Description
This quiz covers the reactions and tests involving alcohols and carboxylic acids, particularly focusing on esterification and identification of functional groups. Understand the reaction mechanisms and the observations that indicate the presence of specific compounds through various chemical tests.
