Volumetric Analysis: Acid-Base Techniques
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Questions and Answers

What is the primary function of a volumetric flask?

  • To deliver an exact volume of solution
  • To mix different solutions together
  • To measure approximate volumes of liquids
  • To contain a definite volume of solution (correct)

    • What must be done to a graduated cylinder before use?

  • It should be rinsed with deionised water (correct)
  • It needs to be dried completely
  • It must be calibrated for temperature
  • It should be filled with deionised water

    • When using a volumetric flask to prepare a solution, how is the last few cm³ of water added?

  • Quickly, to prevent evaporation
  • Carefully, so the meniscus rests on the calibration mark (correct)
  • With a pipette to ensure volume accuracy
  • By pouring directly from a bottle

    • How is a pipette filled with solution?

    <p>By suction, drawing the liquid above the graduation mark</p> Signup and view all the answers

    What is the purpose of inverting a stoppered volumetric flask after filling it?

    <p>To ensure a homogenous mixture</p> Signup and view all the answers

    What is the concentration of the diluted solution obtained from the equation $250 \times M_{dil} = 15 \times 2$?

    <p>0.12 M</p> Signup and view all the answers

    What is a primary standard?

    <p>A substance that can be weighed and dissolved to create a solution of known concentration</p> Signup and view all the answers

    Which of the following is NOT a criterion for a substance to be considered a primary standard?

    <p>Must be able to undergo incomplete reactions</p> Signup and view all the answers

    During the preparation of a standard solution, what is the purpose of rinsing the clock glass with deionised water?

    <p>To ensure all solid is dissolved in the solution</p> Signup and view all the answers

    What should be done after filling the volumetric flask with the solution almost to the calibration mark?

    <p>Add water until the meniscus reaches the mark</p> Signup and view all the answers

    Which of the following steps is essential for ensuring a homogeneous solution?

    <p>Inverting the flask after stoppering</p> Signup and view all the answers

    What is the mass of pure anhydrous sodium carbonate used to prepare the standard solution?

    <p>2.65 g</p> Signup and view all the answers

    Which of the following actions is NOT part of the mandatory experiment to prepare a standard solution?

    <p>Using any available water source</p> Signup and view all the answers

    What is the molar mass of anhydrous sodium carbonate, Na2CO3?

    <p>106 g/mol</p> Signup and view all the answers

    What is the purpose of using a primary standard in a titration?

    <p>To create a solution of known concentration</p> Signup and view all the answers

    How many moles of anhydrous sodium carbonate are present in 2.65g?

    <p>0.0108 moles</p> Signup and view all the answers

    What is the final step in preparing the volumetric solution from the sugar supply?

    <p>Add deionized water until the bottom of the meniscus is on the mark</p> Signup and view all the answers

    What is the color change of methyl orange indicator at the endpoint of the titration?

    <p>Orange to red</p> Signup and view all the answers

    Which of the following steps is NOT part of the titration process?

    <p>Adding water to the burette before starting the titration</p> Signup and view all the answers

    Which reaction occurs when hydrochloric acid is titrated with sodium carbonate?

    <p>2HCl + Na<del>2</del>CO<del>3</del> → 2NaCl + CO<del>2</del> + H<del>2</del>O</p> Signup and view all the answers

    What is the importance of reading the burette at eye level?

    <p>To avoid parallax error</p> Signup and view all the answers

    What is the purpose of rinsing the pipette with deionised water before use?

    <p>To remove any contaminants</p> Signup and view all the answers

    Which step is crucial to prevent splashing when using a conical flask?

    <p>Swirling the flask carefully</p> Signup and view all the answers

    What should be done if the level of liquid in the burette is above the zero mark after filling?

    <p>Remove the funnel and allow some to flow out</p> Signup and view all the answers

    Why is it important to wait a few seconds before removing the pipette from the flask after discharging the solution?

    <p>To ensure all the solution is released</p> Signup and view all the answers

    Why should the burette not be rinsed with the solution it is going to contain?

    <p>It can cause contamination of the solution</p> Signup and view all the answers

    What should the pipette be rinsed with after deionised water?

    <p>Sodium carbonate solution</p> Signup and view all the answers

    What is an essential characteristic of the conical flask design?

    <p>Its shape allows for easy swirling and washing down</p> Signup and view all the answers

    What is the significance of recording the meniscus level at eye level?

    <p>It ensures accurate measurement of volume</p> Signup and view all the answers

    What does a 10% w/v NaCl solution indicate?

    <p>10 g of sodium chloride is dissolved in every 100 cm^3^ of solution.</p> Signup and view all the answers

    How is molarity defined?

    <p>The number of moles of solute per litre of solution.</p> Signup and view all the answers

    What is the correct meaning of 1 ppm?

    <p>1 milligram of solute per litre of solution.</p> Signup and view all the answers

    Which of the following statements about a 1 M (molar) solution is true?

    <p>It contains 1 mole of solute in 1 liter of solution.</p> Signup and view all the answers

    What does the term 'weight per weight' (w/w) mean?

    <p>The grams of solute present in 100 g of solution.</p> Signup and view all the answers

    Which of the following correctly describes a homogenous mixture?

    <p>A mixture where the solute is uniformly distributed throughout the solvent.</p> Signup and view all the answers

    What is the purpose of rinsing the burette with diluted vinegar solution before use?

    <p>To ensure the burette is clean and free of contaminants</p> Signup and view all the answers

    At what point does the phenolphthalein indicator change color during the titration of vinegar with sodium hydroxide?

    <p>When the solution turns colorless</p> Signup and view all the answers

    When conducting a titration, why is it crucial to perform multiple titrations?

    <p>To enhance the accuracy of the results</p> Signup and view all the answers

    What is the expected final concentration of sodium carbonate solution after titration with 0.1 M hydrochloric acid?

    <p>To be calculated from the volume of acid used</p> Signup and view all the answers

    Which indicator is used during the titration of sodium carbonate with hydrochloric acid?

    <p>Methyl orange</p> Signup and view all the answers

    What is the effect of efflorescence on hydrated sodium carbonate crystals?

    <p>They lose water and decrease in mass</p> Signup and view all the answers

    What is the main reason for inverting the volumetric flask after mixing the diluted vinegar?

    <p>To evenly distribute the solute throughout the solvent</p> Signup and view all the answers

    How is the percentage (w/v) of ethanoic acid in the vinegar calculated?

    <p>By using the volume of sodium hydroxide consumed</p> Signup and view all the answers

    Study Notes

    Volumetric Analysis: Acid-Base

    • Volumetric analysis is a quantitative method using solutions.
    • A solution is a homogenous mixture of solute and solvent.
    • Solution concentration can be expressed in different ways.

    Percentage of Solute

    • Weight per weight (w/w): grams of solute per 100 g of solution (g/100g).
      • Example: 10% NaCl w/w means 10 g NaCl per 100 g solution.
    • Weight per volume (w/v): grams of solute per 100 cm³ of solution (g/100 cm³).
      • Example: 10% w/v NaCl means 10 g NaCl per 100 cm³ solution.
    • Volume per volume (v/v): volume of solute per 100 cm³ of solution (cm³/100 cm³).
      • Example: 10% v/v ethanol has 10 cm³ ethanol per 100 cm³.

    Parts per Million (ppm)

    • Used for very dilute solutions.
    • 1 ppm = 1 mg/L

    Moles of Solute per Liter of Solution (Molarity)

    • Molarity is the number of moles of solute per litre of solution.
    • 1 M solution contains 1 mole of solute per litre of solution.

    Converting Moles per Liter to Grams per Liter

    • To convert moles per liter to grams per liter, multiply by the molar mass.
    • Example: 0.25 M NaCl solution contains 14.625 g/L NaCl.

    Converting Grams per Liter to Moles per Liter

    • To convert grams per liter to moles per liter, divide by the molar mass.
    • Exmaple: Solution that contains 3.68 g NaOH per liter of solution is 0.092 M.

    Calculating the Number of Moles

    • Number of moles = volume × molarity / 1000
    • Example: 25 cm³ of 0.55M NaOH contains 0.014 moles NaOH.

    Dilution of Solutions

    • Moles of solute in diluted solution = Moles of solute in concentrated solution.
    • (Volume of diluted solution)(Molarity of diluted solution)/1000 = (Volume of concentrated solution)(Molarity of concentrated solution)/1000
    • Example: 250 cm³ of 12 M HCl to make 500 cm³ of 3 M HCl requires 100 cm³ of 12M HCl.

    Reaction between a Solution and a Solid

    • Example: Mass of magnesium that reacts with 50 cm³ of 0.5 M H₂SO₄ is 0.6 g.

    Standard Solutions

    • Standard solution: A solution with accurately known concentration.

    Primary Standard

    • Primary standard: A pure, stable and soluble solid that can be weighed to accurately prepare a solution.

    Mandatory Experiment: Preparing a Standard Solution of Sodium Carbonate

    • Detailed steps for preparing a standard sodium carbonate solution.

    Volumetric Analysis: Titration

    • Definition: Measurement of one solution with another.
    • Titration apparatus: Graduated cylinders, Volumetric flasks, Pipettes, Conical Flask.

    The Pipette:

    • Exact volume measurement.
    • Using a pipette filler.

    Conical Flask:

    • Designed for swirling.
    • Should not be washed directly with solution.

    Mandatory Experiment: Standard Solution of Sodium Carbonate to Standardize Hydrochloric Acid Solution

    • Detailed step-by-step procedure of titration experiment

    Mandatory Experiment: Determining Ethanoic Acid in Vinegar

    • Detailed steps for calculating concentration of ethanoic acid in vinegar.

    Mandatory Experiment: Determining the amount of water of crystallisation in hydrated sodium carbonate

    • Steps for finding the amount of water of crystallisation of sodium carbonate.

    Exam Questions (2014)

    • Detailed analysis of exam questions pertaining to washing soda crystals.

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    Volumetric Analysis PDF

    Description

    This quiz covers the fundamentals of volumetric analysis, focusing on acid-base solutions. You'll learn about various ways to express solution concentration, including weight/weight, weight/volume, and molarity. Test your understanding of these concepts and improve your analytical skills.

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