Volumetric Analysis: Oxidation-Reduction
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Match the following compounds with their roles in volumetric analysis:

Potassium permanganate = Oxidising agent Iron(II) ions = Reducing agent Ammonium iron (II) sulfate = Primary standard Sulfuric acid = Source of H+ ions

Match the following descriptions with the respective compounds used in titration:

KMnO4 = Acts as its own indicator Fe2+ = Converted to Fe3+ Ammonium iron (II) sulfate = High purity and stable in air

Match the following steps with their corresponding actions in the experiment:

Rinse burette = With potassium manganate(VII) solution Fill pipette = With iron(II) solution Acidify conical flask = Add dilute sulfuric acid Adjust burette = To zero before titration

Match the following ions with their respective redox changes:

<p>MnO4^- = Mn2+ Fe2+ = Fe3+ H+ = No change MnO4^- with Fe2+ = Requires 5 Fe2+ ions</p> Signup and view all the answers

Match the following laboratory equipment with their usage in the experiment:

<p>Pipette = Transfer iron(II) solution Burette = Deliver potassium manganate(VII) solution Conical flask = Hold the reaction mixture White tile = Enhance visibility of color change</p> Signup and view all the answers

Match the following reactions with their appropriate electron transfer details:

<p>MnO4^- + 8H+ + 5e^- → Mn2+ = Oxidation process Fe2+ → Fe3+ + e^- = Reduction process MnO4^- + 5Fe2+ + 8H+ → Mn2+ + 5Fe3+ + 4H2O = Overall redox reaction Fe2+ + e^- → Fe3+ = Electrons lost</p> Signup and view all the answers

Match the following factors with their relevance in the titration process:

<p>Precision = Accurate measurements critical Concentration = Determines rate of color change Purity = Ensures reliable results Indicator = Indicates endpoint during titration</p> Signup and view all the answers

Match the following characteristics with the substances in the titration:

<p>Potassium permanganate = Intense purple color Iron(II) ions = Pale green solution Sulfuric acid = Colorless liquid Ammonium iron (II) sulfate = Stable under air exposure</p> Signup and view all the answers

Match the following laboratory techniques with their descriptions:

<p>Titration = Determining the concentration of a solution Filtration = Separating solids from liquids Evaporation = Concentrating solutions by removing solvent Distillation = Separating components based on boiling points</p> Signup and view all the answers

Match the reactants in the redox reaction with their roles:

<p>MnO4^- = Oxidizing agent Fe^2+ = Reducing agent H+ = Acid catalyst H2O = Product of the reaction</p> Signup and view all the answers

Match the variables with their definitions in volumetric analysis:

<p>Vo = Volume of oxidizing agent Vr = Volume of reducing agent Mo = Molarity of oxidizing agent Mred = Molarity of reducing agent</p> Signup and view all the answers

Match the chemical compound with its formula:

<p>Potassium permanganate = KMnO4 Sulfuric acid = H2SO4 Ammonium iron(II) sulfate = (NH4)2Fe(SO4)2·6H2O Water = H2O</p> Signup and view all the answers

Match the mass concentration values with their units:

<p>0.12 M = Moles per liter 3.997 g/L = Grams per liter 25 cm^3 = Volume measurement 158 g/mol = Molar mass</p> Signup and view all the answers

Match the steps in preparing a solution with their order:

<p>Crush iron tablets = Step 2 Weigh iron tablets = Step 1 Dissolve in sulfuric acid = Step 2 Make up to the mark = Step 3</p> Signup and view all the answers

Match the end-point observation with the technique used:

<p>Pale pink color = Titration Gas bubbles = Filtration Crystals forming = Evaporation Liquid separation = Distillation</p> Signup and view all the answers

Match the term with its corresponding value in the titration:

<p>Average titration figure = 23.75 cm^3 Moles of Fe^2+ = 5 Moles of Mn^O4^- used = 1 Iron tablet mass = Measured in grams</p> Signup and view all the answers

Match the following solutions with their uses in the experiment:

<p>Iron(II) solution = Reactant for titration Potassium manganate(VII) = Titrant solution Dilute sulfuric acid = Acidifying agent Deionised water = Washing and rinsing</p> Signup and view all the answers

Match the following steps with their corresponding actions:

<p>Wash pipette, burette, and flask = Preparation for titration Fill pipette with iron(II) solution = Sample transfer Fill burette with potassium manganate(VII) = Setting up titration Add solution from burette to flask = Conduct titration</p> Signup and view all the answers

Match the following indicators with their descriptions:

<p>First persisting pink colour = End-point of titration White tile = Surface for observing color change Dropwise addition = Approaching end-point cautiously Meniscus reading = Accurate volume measurement</p> Signup and view all the answers

Match the following substances with their properties:

<p>Iron(II) ions = Reduced state of iron MnO4^- ions = Oxidizing agent Fe^3+ ions = Oxidized state of iron H^+ ions = Acidic environment</p> Signup and view all the answers

Match the following measurements with their values:

<p>Total mass of five tablets = 1.2 grams Volume used in titration = 5.75 cm^3 Volume of solution made up to = 250 cm^3 Volume of sample taken for titration = 25 cm^3</p> Signup and view all the answers

Match the following components with their associated calculations:

<p>Concentration of KMnO4 = 0.015 M Moles of MnO4^- reacted = 1 mole Stoichiometry ratio of MnO4^- to Fe^2+ = 1:5 Calculated moles of iron in 25 cm^3 = 0.0173 moles</p> Signup and view all the answers

Match the following chemical reactions with their products:

<p>MnO4^- + Fe^2+ = Mn^2+ + Fe^3+ MnO4^- + H^+ = Mn^2+ + H2O Fe^2+ oxidation = Fe^3+ H^+ neutralization = Water formation</p> Signup and view all the answers

Match the following terms with their definitions:

<p>Titration = Quantitative chemical analysis method Stoichiometry = Study of reactant ratios Endpoint = Conclusion of titration process Concentration = Amount of solute per volume of solution</p> Signup and view all the answers

Match the following formulas with their respective compounds:

<p>FeSO₄ = Iron(II) sulfate Na₂S₂O₃·5H₂O = Sodium thiosulfate pentahydrate KIO₃ = Potassium iodate H₂SO₄ = Sulfuric acid</p> Signup and view all the answers

Match the following laboratory equipment with their uses:

<p>Pipette = To measure and transfer precise volumes of liquid Burette = To dispense variable amounts of liquid, especially during titration Conical flask = To mix and swirl solutions during titration Graduated cylinder = To measure volumes of liquids accurately</p> Signup and view all the answers

Match the following calculation results with their corresponding parameters:

<p>Mass of iron in each tablet = 0.049 g Percentage of iron in FeSO₄ = 36.84% Mass of one tablet = 0.24 g % FeSO₄ in each tablet = 55%</p> Signup and view all the answers

Match the substances with their roles in the titration procedure:

<p>Sodium thiosulfate = Titrant used to standardize against iodine Potassium iodate = Analyte solution reacted in the conical flask Sulfuric acid = Acidifier for the reaction Starch solution = Indicator for the endpoint of the titration</p> Signup and view all the answers

Match the following volume measurements with their conversions:

<p>25 cm³ = 0.025 L 250 cm³ = 0.250 L 20 cm³ = 0.020 L 27.45 cm³ = 0.02745 L</p> Signup and view all the answers

Match the following steps with their order in the titration process:

<p>Rinse equipment = 1 Add starch indicator = 6 Note burette reading = 7 Repeat procedure for consistency = 8</p> Signup and view all the answers

Match the calculation tasks with their formulas:

<p>Concentration of sodium thiosulfate (moles/L) = $\frac{C_1V_1}{V_2}$ Mass of sodium thiosulfate (grams/L) = $\text{Moles} \times \text{molar mass}$ Percentage of FeSO₄ in tablet = $\frac{0.132}{0.24} \times 100$ Mass of FeSO₄ in volumetric flask = $\frac{2.63}{4}$</p> Signup and view all the answers

Match the following terms with their definitions related to the titration process:

<p>Starch = Indicator used to determine the endpoint of a titration Thiosulfate = Chemical used to react with iodine in titrations Conical flask = Container used to hold the solution during titration White tile = Surface used to enhance visibility of color change</p> Signup and view all the answers

Match the following compounds with their functions in the titration experiment:

<p>NaClO = Active ingredient in bleach Iodine = Oxidizing agent that is reduced in the reaction Sodium thiosulfate = Reducing agent that reacts with iodine Potassium iodide = Keeps iodine in solution for the reaction</p> Signup and view all the answers

Match the following values with their respective calculations or outcomes:

<p>16.1 cm³ = Average volume of sodium thiosulfate required 0.0322 moles/L = Concentration of NaClO in diluted bleach 47.978 g/L = Concentration of NaClO in original bleach in grams per litre 4.7978 % (w/v) = Concentration of NaClO as a percentage (w/v)</p> Signup and view all the answers

Match the following chemical species with their roles in the titration reaction:

<p>I₂ = Substance that is reduced by sodium thiosulfate S₂O₃²⁻ = Ion that serves as a reducing agent S₄O₆²⁻ = Product formed after reaction with iodine I⁻ = Iodide ion produced as a product during the titration</p> Signup and view all the answers

Match the following statements with their corresponding reasons during the titration procedure:

<p>Standing conical flask on a white tile = Improves visibility of the color change Use of excess potassium iodide = Ensures complete reaction with all bleach present Addition of sodium thiosulfate = Determines the end-point of the titration Color change from blue to colourless = Indicates the completion of the reaction with starch</p> Signup and view all the answers

Match the following concentrations with their corresponding types:

<p>0.077 moles per litre = Concentration of NaClO in diluted bleach 0.77 moles per litre = Concentration of NaClO in original bleach 57.37 g NaClO per litre = Mass concentration of NaClO in original bleach 5.74 % w/v = Weight/volume percentage of NaClO in original bleach</p> Signup and view all the answers

Match the following steps with their descriptions in the dilution process:

<p>Pipette = Transfer exact volume of bleach to volumetric flask Add deionised water = Fill the flask until it approaches the graduation mark Read at eye level = Ensure accurate measurement of liquid height Invert several times = Mix the solution to ensure homogeneity</p> Signup and view all the answers

Match the following chemical reactions with their respective products:

<p>ClO^- + 2I^- + 2H^+ = Cl^- + I2 + H2O 2S2O3^2- + I2 = S4O6^2- + 2I^- Reaction with Sulfuric acid = Generation of iodine Potassium iodide = Provides I^- ions for the reaction</p> Signup and view all the answers

Match the following quantities with their calculated values:

<p>Volume of diluted bleach = 500 cm^3 Initial volume of bleach used = 25 cm^3 Volume used for titration = 25.0 cm^3 Molecular mass of NaClO = 74.5 g/mol</p> Signup and view all the answers

Match the following steps with their outcomes in the titration process:

<p>Using a pipette = Accurate measurement of diluted bleach Titration against Na2S2O3 = Determining concentration of NaClO Adding sulfuric acid = Acidifying the solution for reaction Excess of potassium iodide = Ensures all available ClO^- reacts</p> Signup and view all the answers

Match the following concentration types with their appropriate formula:

<p>Molarity (M) = $ rac{moles}{volume ext{ (L)}}$ Mass concentration = $ rac{grams}{volume ext{ (L)}}$ Weight/volume percentage (w/v) = $ rac{grams}{100 ext{ cm}^3}$ Dilution factor = $ rac{V_{original}}{V_{diluted}}$</p> Signup and view all the answers

Match the following titration components with their roles:

<p>Conical flask = Holds the reaction mixture for titration Burette = Delivers titrant solution during titration Indicator = Signals endpoint of titration Titrant = Solution of known concentration</p> Signup and view all the answers

Match the following reactions with their respective reagents:

<p>ClO^- and I^- ions = Oxidation-reduction reaction Thiosulfate ion = Reduces iodine back to iodide Sulfuric acid = Provides H^+ for the reaction Potassium iodide = Serves as a source of I^-</p> Signup and view all the answers

Flashcards

Titration Endpoint

The point in a titration where the reaction between the two solutions is complete, marked by a noticeable change (e.g., color change).

Potassium Permanganate (KMnO4)

A strong oxidizing agent commonly used in titrations.

Molarity (M)

A measure of concentration, expressing the number of moles of solute per liter of solution.

Redox Reaction

A chemical reaction involving both oxidation and reduction.

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Volumetric Analysis

A method used for determining the concentration or amount of a substance using measurement of volumes.

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Standardization (Titration)

Using a solution of known concentration to determine the concentration of an unknown solution.

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Volumetric Flask

A laboratory glassware used to prepare solutions with accurate volumes.

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Dilute Sulfuric Acid

A weak acid used in dissolving iron tablets and preparing solutions.

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Oxidizing Agent

A substance that gains electrons in a chemical reaction, causing another substance to lose electrons.

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Reducing Agent

A substance that loses electrons in a chemical reaction, causing another substance to gain electrons.

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Primary Standard

A substance with a known, very high purity, used to determine the concentration of another solution.

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Standardization

The process of determining the exact concentration of a solution using a known standard.

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Titration

A lab technique to determine the concentration of a solution by reacting it with a solution of known concentration.

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Ammonium Iron(II) Sulfate

A substance used as a primary standard in titrations involving iron(II) ions.

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Reaction of MnO4- and Fe2+ ions

MnO4- (a powerful oxidizer) oxidizes Fe2+ ions to Fe3+ ions, a key reaction in volumetric analysis.

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Iron(II) solution

A solution containing iron ions with a +2 oxidation state.

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Endpoint detection

"The first persisting pink colour" of the indicator in a titration.

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Iron tablets analysis

Determining the amount of iron in a tablet for accuracy.

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Molarity

A measure of concentration, expressing moles of solute per liter of solution (mol/L).

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Stoichiometry

Calculations about the amounts of substances involved in a balanced chemical reaction, based on their respective moles.

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Excess Potassium Iodide

Used to ensure all the bleach (NaClO) reacts and to keep the iodine in solution.

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Purpose of White Tile

A white tile is used to provide a contrasting background, making the colour change in the titration more visible and easier to detect the endpoint.

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Starch Indicator

Starch is used as an indicator in the titration. It forms a blue complex with iodine, which disappears when the iodine reacts with thiosulfate, indicating the end point.

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Calculating Concentration

The concentration of NaClO is calculated using the titration data and the balanced chemical equation. The amount of thiosulfate used is proportional to the amount of iodine produced, which is in turn proportional to the amount of NaClO present.

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Concentration Units

The concentration of NaClO can be expressed in different units, such as moles per liter (mol/L) or grams per liter (g/L). A percentage weight per volume (% w/v) is also commonly used.

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Endpoint

The point in a titration where the chemical reaction between the two solutions is complete, marked by a noticeable change, usually a color change.

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Calculate Concentration (using titration)

Using the volumes and molarity of the known and unknown solutions in a titration, we can calculate the concentration of the unknown solution.

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Sodium Thiosulfate (Na2S2O3.5H2O)

A chemical used in titrations, often to react with iodine, creating a color change used to determine the endpoint.

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Potassium Iodate (KIO3)

A chemical used in titration reactions, often to provide iodine that reacts with the sodium thiosulfate.

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What is the balanced chemical equation for the reaction between hypochlorite ions and iodide ions?

ClO^- + 2I^- + 2H^+ → Cl^- + I2 + H2O

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What is the purpose of titrating with sodium thiosulfate?

Sodium thiosulfate (Na2S2O3) reacts with iodine (I2) produced in the reaction between bleach and iodide, allowing for the determination of the concentration of hypochlorite in the bleach solution.

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Dilution Factor

The ratio of the final volume of a diluted solution to the initial volume of the original solution.

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How to calculate the concentration in moles per litre (Molarity)?

Molarity is calculated by dividing the number of moles of solute by the volume of the solution in liters.

M = moles / volume (L)

For example, if you have 0.5 moles of solute dissolved in 1.0 liter of solution, the molarity would be 0.5 M.

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How to convert from moles per litre to grams per litre?

Multiply the molarity by the molar mass of the solute. This gives you the mass of the solute in grams per litre of the solution.

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How to calculate %w/v? (weight/volume percentage)

%w/v is calculated by dividing the mass of the solute in grams (g) by the volume of the solution in millilitres (mL) and then multiplying by 100.

%w/v = (mass of solute (g) / volume of solution (mL)) x 100

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How to calculate the concentration in the original bleach?

The concentration of the original bleach is determined by multiplying the concentration of the diluted bleach by the dilution factor.

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What is the purpose of potassium iodide and sulfuric acid in the reaction?

Potassium iodide (KI) provides iodide ions (I-) which react with hypochlorite ions (ClO-) in the presence of acid (H+). This reaction produces iodine (I2) causing a color change.

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Study Notes

Volumetric Analysis: Oxidation-Reduction

  • Volumetric analysis determines oxidizing and reducing agent concentrations.
  • Potassium permanganate (KMnO4) is a crucial oxidizing agent.
  • KMnO4 is a purple solid, but not a primary standard due to purity issues.
  • It needs standardization via titration against a primary standard.
  • KMnO4 gains 5 electrons in acidic solution.
    • MnO4- + 8H+ + 5e- → Mn2+ + 4H2O
  • H+ ions are needed for the reaction; dilute acid is added.
  • KMnO4 acts as its own indicator.
  • Fe2+ ions can be used to determine KMnO4 concentration.
  • KMnO4 oxidizes Fe2+ to Fe3+.
    • MnO4- + 8H+ + 5Fe2+ → Mn2+ + 5Fe3+ + 4H2O
  • Ammonium iron(II) sulfate (a primary standard) provides Fe2+ ions.
  • It's crucial for preparing a standard FeSO4 solution to standardize KMnO4.
  • Titration procedures are needed to standardize KMnO4 solution using a standardized Fe2+ solution.

Mandatory Experiment: Preparing Standard Solution

  • Materials: Deionized water, burette, conical flask, pipette
  • Procedure:
    1. Wash glassware. Rinse burette and pipette with KMnO4 and Fe2+ solutions.
    2. Pipette measured Fe2+ solution into the conical flask. Add sulfuric acid.
    3. Fill burette with KMnO4 solution, ensuring below the tap is filled before zero adjustment.
    4. Add standard KMnO4 to the conical flask to detect endpoint (first persisting pale pink color). Titrating must be consistent, use a wash bottle to wash down the walls of the flask. Record results.

Solving Volumetric Problems in Redox Reactions

  • Formulae for calculating concentration of oxidizing and reducing agents
    • Vox, Mox, nox
    • Vred, Mred, nred

Mandatory Experiment: Determining Iron content in an Iron Tablet

  • Find the total mass of five iron tablets
  • Crush the tablets and dissolve in sulfuric acid
  • Transfer solution to a 250-cm³ volumetric flask and dilute
  • Use a pipette to take a known volume of the solution
  • Titrate against a standard KMnO4 solution until the endpoint
  • Calculate iron concentration and mass
  • Calculate the percentage of iron in an iron tablet

Mandatory Experiment: Determining Sodium Thiosulfate Concentration

  • Standard solution of sodium thiosulfate and standard iodine solution is needed.
  • Using a pipette: fill a pipette with potassium iodate solution and transfer to conical flask.
  • Add sulfuric acid.
  • Add potassium iodide solution.
  • Fill burette with sodium thiosulfate solution, ensuring the portion below the tap is filled before adjusting to zero.
  • Add sodium thiosulfate to the conical flask to detect endpoint.
  • Calculate sodium thiosulfate concentration

Mandatory Experiment: Determining Percentage of Sodium Hypochlorite in Household Bleach

  • Dilute bleach solution first.
  • Wash and rinse pipette. Wash burette with sodium thiosulfate.
  • Add 1 g potassium iodide and 10 cm³ of dilute sulfuric acid to conical flask.
  • Titrate with the standard sodium thiosulfate solution.

Exam Questions (2011)

  • Questions on dilutions, calculations, descriptions of procedures, color changes, etc. for determining sodium hypochlorite concentration in bleach.
  • Using a titration procedure to identify and determine the concentration of a solution.

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Description

This quiz delves into the principles of volumetric analysis focusing on oxidation-reduction reactions. It highlights the role of potassium permanganate (KMnO4) as an oxidizing agent and its interaction with Fe2+ ions. Test your understanding of titration techniques and the use of primary standards in determining concentrations!

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