Volumetric analasis

• What is volumetric analysis?

  Volumetric analysis is a method of analysis that involves reading volumes of solutions with each other.
• What is formed when a solute dissolves in a solvent?

  A solution is formed, which is a homogeneous mixture of the solute and solvent.
• What is the definition of a homogeneous mixture?

  A homogeneous mixture is one where the particles of the solute are uniformly distributed throughout the solvent.
• How is a concentrated solution defined?

  A concentrated solution has a large amount of solute relative to the volume of solvent.
• What characterizes a dilute solution?

  A dilute solution has a small amount of solute relative to the volume of solvent.
• What is the concentration of a solution?

  The concentration of a solution is the exact measure of the amount (mass) of solute in a certain volume of solution.
• How can the concentration of a solution be expressed?

  Concentration can be expressed in several ways, including percentage of solute, parts per million, molarity, and grams per liter.
• What are the common ways to express the concentration of a solution?


  • Percentage of solute (% w/w, % w/v, % v/v)
  • Parts per million (ppm)
  • Molarity (moles of solute per liter of solution)
  • Grams of solute per liter of solution (g/L)
• What does % w/w represent in concentration?

  % w/w represents the number of grams of solute in 100 g of solution.
• What does % w/v represent in concentration?

  % w/v represents the number of grams of solute in 100 cm³ of solution.
• What does ppm stand for and how is it expressed?

  ppm stands for parts per million and is expressed as mg/L for very small concentrations.
• What is molarity (M) in terms of concentration?


  Molarity (M) is the number of moles of solute per liter of solution.
• How do you convert grams per liter to molarity?

  To convert grams per liter to molarity, divide by the relative molecular mass of the solute.
• How do you convert molarity to grams per liter?

  To convert molarity to grams per liter, multiply by the relative molecular mass of the solute.
• What is the procedure to prepare a solution of a primary standard?

  1. Weigh a known mass of anhydrous Na₂CO₃ on a clock glass using an accurate balance.
  2. Transfer to a beaker containing deionised water.
  3. Wash the clock glass down into the beaker.
  4. Stir the solution to dissolve completely.
  5. Transfer to a 250 cm³ volumetric flask using a funnel.
  6. Wash down the beaker and funnel into the flask.
  7. Add deionised water until just below the graduation mark.
  8. Add deionised water dropwise until the bottom of the meniscus is on the mark at eye level.
  9. Stopper the flask and invert 20 times to create a homogeneous solution.
• What is a standard solution?

  A standard solution is a solution whose concentration is accurately known.
• Why is it difficult to prepare a solution of NaOH of precisely known concentration?

  NaOH is deliquescent and absorbs water from the atmosphere, making it difficult to weigh accurately.
• What is a primary standard?

  A primary standard is a substance that can be obtained in a stable, pure, and soluble solid form to give a solution of accurately known concentration.
• What are the characteristics of a primary standard?

  • Must be available in a highly pure state.
  • Must be stable (not lose or absorb water).
  • Must dissolve easily in water.
  • Should have a high relative molecular mass for precision in weighing.
  • Should undergo complete and rapid reaction in volumetric analysis.
  • Must be anhydrous (no water of crystallization).
• What is the purpose of volumetric analysis?

  The purpose of volumetric analysis is to find the unknown concentration of a solution by reacting it with a solution of known concentration.
• How is a solution of a primary standard used in volumetric analysis?

  A solution of a primary standard is used to find the exact concentration of another solution, such as HCl.
• What are the features and uses of volumetric analysis apparatus?

  1. Graduated Cylinder:

  • Used for measuring approximate volumes.
  • Wash with deionised water.
  • Read at eye level.
  • Rinse after use.

  
  

  1. Volumetric Flask:

  • Used for preparing accurate fixed volumes of solutions.
  • Wash with deionised water.
  • Must be inverted 20 times for homogeneity.

  
  

  1. Pipette:

  • Used for measuring and delivering exact volumes.
  • Wash with deionised water.
  • Fill using a pipette filler.

  
  

  1. Burette:

  • Used for measuring and delivering exact volumes.
  • Wash with deionised water.
  • Clamped vertically and filled above the zero mark.
• Why should the last few drops of deionised water be added dropwise when filling a volumetric flask?

  To ensure the bottom of the meniscus is on the graduation mark for accurate concentration.
• What should be done after using a pipette?

  The pipette should be rinsed with deionised water and allowed to drain.
• How should a burette be filled?

  A burette should be filled using a funnel, filled to above the zero mark, and then the tap opened to fill the tip.
• Why should bases not be used in burettes without proper washing?

  Bases can react with CO₂ in the air if not washed out properly, affecting the concentration.
• What is the purpose of washing the burette with deionised water before use?


  To remove any impurities that could affect the results
• Why should the burette be clamped vertically in a retort stand?

  To ensure accurate measurement of the solution being delivered
• What should be done after filling the burette above the zero mark?


  The funnel should be removed and the tap opened to fill the tip
• What is the significance of the meniscus in burette readings?

  The bottom of the meniscus should be at eye level for accurate measurement
• Why are bases typically not used in burettes?

  They can react with CO₂ in the air and form a crust around the tap
• What is the purpose of swirling the conical flask during a titration?

  To ensure thorough mixing of the solutions
• What is the role of the indicator in a titration?

  To signal the end point of the titration by changing color
• What happens at the end point of a titration?

  The indicator changes color, indicating that the reaction is complete
• How is the titre value determined during a titration?

  By noting the volume of solution added from the burette at eye level
• What is the difference between a rough titration and accurate titrations?

  A rough titration provides an approximate titre value, while accurate titrations are repeated to find precise values
• What is the purpose of diluting the vinegar solution in the titration of ethanoic acid?

  To ensure accurate readings and reduce the high concentration of acid
• How is the dilution factor calculated?


  By comparing the volume of the original solution to the final volume after dilution
• What is the balanced equation for the reaction between sodium carbonate and hydrochloric acid?

  Na₂CO₃ + 2 HCl → 2 NaCl + CO₂ + H₂O
• What is the role of methyl orange in the titration of hydrochloric acid with sodium carbonate?

  Methyl orange indicates the end point by changing color from orange to pink