Standard Solutions

• What is the unit used to measure concentration?

  mol dm³
• How do you convert 200 cm³ into dm³?

  200 cm³ = 0.2 dm³
• What is a solute?

  A substance dissolved in a solution
• What is a solvent?

  A substance that dissolves a solute
• What is a solution?

  A homogeneous mixture of solute and solvent
• What mass of H₂SO₄ is needed for 100.0 cm³ of 0.250 mol dm³ solution?

  Mass = 2.45 g
• What is the concentration of 3.65 g of HNO₃ in 100 cm³ of water?

  Concentration = 0.50 mol dm³
• What is a standard solution?

  A solution with a known concentration
• What is deionised water?

  Water that has had ions removed
• What apparatus is used for volumetric analysis?

  Volumetric flask
• What is the resolution of the volumetric flask mentioned?

  10 ml
• What is the process of making a standard solution?

  1. Measure mass of empty weighing boat
  2. Measure desired mass of solid
  3. Transfer solid to beaker
  4. Dissolve solute in small solvent amount
  5. Transfer to volumetric flask
  6. Make up to the mark with solvent
• What is the inherent uncertainty in measurements?

  Every measurement has some uncertainty
• How is uncertainty assessed from an instrument's resolution?

  It indicates the minimum possible uncertainty
• What distinguishes readings from measurements?

  Readings involve one judgement; measurements involve two
• What is the uncertainty in a thermometer reading?

  ±0.5 °C
• What is the uncertainty for a burette reading?

  ±0.05 cm³
• How do you calculate percentage uncertainty?

  Percentage uncertainty = uncertainty / value x 100%
• What is the total uncertainty for a standard solution of 250 ml?

  0.13%
• What are the steps in preparing a sodium carbonate solution?

  1. Weigh a clean dry weighing boat
  2. Add calculated sodium carbonate mass
  3. Weigh the bottle with contents
  4. Transfer contents to a beaker
  5. Add de-ionised water and stir
  6. Pour into volumetric flask and rinse
  7. Fill to graduated mark and mix
• What should be recorded during the preparation of a standard solution?

  All weighings to the precision of the balance
• How do you ensure the sodium carbonate dissolves completely?

  Stir the solution with a glass rod
• What is the importance of rinsing the beaker and funnel into the volumetric flask?

  To ensure all solute is transferred
• Why is it important to stopper the volumetric flask after preparation?

  To prevent contamination and evaporation
• What should be done after making the volumetric flask up to the mark?

  Stopper and shake the flask thoroughly
• What calculations are required after preparing the solution?

  Calculate exact concentration and % uncertainty