C5.1 Monitoring chemical reactions

• What is the focus of section C5 in the study material?

  Monitoring and controlling chemical reactions
• What is the theoretical yield?


  The maximum amount of product that can be produced from a given amount of reactants
• How can you calculate the theoretical yield?

  By using the balanced equation and the molar masses of the reactants and products
• What are the steps to calculate the theoretical yield?

  1. Calculate the moles of the reactants and products.
  2. Use the balanced equation to find the ratios.
  3. Calculate the theoretical yield using the mass of the limiting reactant.
• If 120g of carbon is burned completely, how do you calculate the theoretical yield of carbon dioxide?

  By using the balanced equation and the molar mass of carbon dioxide
• What is the formula for calculating percentage yield?

  Percentage yield = (actual yield / theoretical yield) x 100
• What does a percentage yield of less than 100% indicate?

  That not all reactants were converted into products
• What factors can affect the percentage yield of a reaction?

  Incomplete reactions, side reactions, and product loss during separation
• What is atom economy?

  • A measure of the efficiency of a reaction
  • Calculated as:

  \[

  \text{Atom Economy} = \left( \frac{\text{Molar mass of desired product}}{\text{Sum of molar masses of all reactants}} \right) \times 100

  \]
• What is the atom economy of a reaction with a desired product molar mass of 90 g/mol and reactants with a total molar mass of 240 g/mol?

  37.5%
• What does a low atom economy indicate?

  That a large proportion of reactants are converted into by-products
• How does the choice of reaction pathway affect the production of a substance?

  It can influence the yield, atom economy, and cost of production
• What factors determine how you make a substance?

  • Cost of raw materials
  • Yield and atom economy
  • Environmental impact
  • Availability of by-products
• What is the significance of by-products in chemical reactions?

  They can sometimes be sold or used in other processes
• What is the overall yield of the epoxyethane production process mentioned?

  About 30%
• How do you calculate concentrations in g/dm³?

  Concentration (g/dm³) = mass of solute (g) / volume of solution (dm³)
• If you have 45g of solute in 250 cm³ of solution, what is the concentration in g/dm³?

  180 g/dm³
• How do you convert cm³ to dm³?

  By dividing the volume in cm³ by 1000
• How do you calculate the concentration in mol/dm³?

  Concentration (mol/dm³) = amount of solute (mol) / volume of solution (dm³)
• What is a titration?

  A technique used to determine the concentration of a solution by adding a reactant of known concentration
• What are the key steps in performing a titration?

  1. Measure a known volume of the solution of unknown concentration.
  2. Add a few drops of indicator.
  3. Slowly add the titrant from a burette until the endpoint is reached.
  4. Record the volume of titrant used.
  5. Calculate the concentration of the unknown solution.
• What is the volume of the solution mentioned in the study material?

  500 cm³ of solution
• What is the process for converting between concentration units?

  • Identify the concentration in mol/dm³.
  • Use the equation to calculate the amount of solute in moles.
  • Convert the units as necessary.
• How do you convert concentration from mg/dl to g/dm³?

  Divide the value by 1000.
• What is the concentration in g/dm³ of a solution containing 0.75 g of solute in 150 cm³ of solution?


  5 g/dm³
• How do you calculate the amount of solute in moles in a 2 dm³ solution with a concentration of 0.5 mol/dm³?

  1 mol of solute
• What is the volume of a 2 mol/dm³ solution that contains 0.5 mol of solute?

  0.25 dm³
• How much potassium iodide (KI) is needed for a 500 ml solution of 301.75 mmol/dm³?

  15.0875 g of potassium iodide
• What is a titration?

  A titration is a method to determine the concentration of a solution by adding a reactant of known concentration until the reaction reaches completion.
• What is often used in titrations for standard solutions?

  NaCl (sodium chloride)
• Why is a volumetric pipette preferred over a measuring cylinder in titrations?

  Because a volumetric pipette provides more accurate measurements.
• What should be worn throughout the titration procedure for safety?

  Eye protection
• What precautions are needed to obtain a reliable titration result?

  • Use a volumetric pipette for accurate measurement.
  • Clamp the burette vertically for accurate readings.
  • Add a few drops of indicator to the solution.
• How do you calculate the mean titre from repeated titration results?

  Add the concordant titres and divide by the number of titres.
• What is the molar volume of a gas at room temperature and pressure (RTP)?

  24 dm³/mol
• How do you calculate the amount of gas in moles if you know its volume at RTP?

  Use the formula: Amount (mol) = Volume (dm³) / 24.
• How do you measure the volume of gas produced in a reaction?

  Use a measuring cylinder filled with water and record the volume of gas displacing the water.
• What should be done to prevent air from affecting the volume reading in gas measurement?

  Keep the mouth of the measuring cylinder underwater.
• How do you calculate the concentration of a solution if you know the amount of solute and the volume of solution?

  Use the formula: Concentration (mol/dm³) = Amount (mol) / Volume (dm³).
• What are the steps involved in a titration calculation?

  1. Convert all volumes to dm³.
  2. Calculate the amount of solute in moles using the concentration and volume.
  3. Use the balanced equation to find the amount of the other reactant.
  4. Calculate the concentration of the other reactant.