Titrations and calculations

• What is the procedure to carry out an acid-alkali titration?


  Measure the volume of acid and alkali, add an indicator, and titrate until the endpoint is reached.
• How do you calculate the number of moles of solute in a given volume of solution?


  Use the formula: number of moles = concentration (mol dm⁻³) × volume (dm³).
• How do you calculate the concentration of a solution using the results of an acid-alkali titration?

  Concentration = number of moles of solute / volume of solution in dm³.
• What indicator was used in the titration of sodium hydroxide solution?

  Methyl orange
• What is the colour change of methyl orange at the end-point of a titration?


  It changes from red to yellow.
• What are some uses of titrations?


  • Testing water samples
  • Analyzing foodstuffs
  • Analyzing drugs
• What is the balanced equation for the reaction between sulfuric acid and potassium hydroxide?

  H₂SO₄ + 2KOH → K₂SO₄ + 2H₂O
• If 25.0 cm³ of potassium hydroxide solution was neutralised by 15.0 cm³ of 0.150 mol dm⁻³ hydrochloric acid, how do you calculate the concentration of the potassium hydroxide solution?


  Use the formula: concentration = number of moles of KOH / volume of KOH solution in dm³.
• What is the mole ratio in the reaction between hydrochloric acid and sodium hydroxide?


  The mole ratio is 1:1.
• How do you calculate the number of moles of hydrochloric acid used in a titration?


  Number of moles = concentration of HCl × volume of HCl used (in dm³).
• What is the concentration of sodium hydroxide if 0.00200 mol of NaOH reacted with 25.0 cm³ of solution?


  Concentration = $\frac{0.00200}{0.0250} =$$0.0800 \text{ mol dm}^{-3}$
• How can you calculate the volume of one solution that will react with a given volume of another in a titration?


  You need to know the concentrations of both solutions and the balanced equation.
• If 250 cm³ of 0.200 mol dm⁻³ sodium hydroxide solution was neutralised by sulfuric acid, how do you calculate the volume of sulfuric acid needed?


  Use the mole ratio from the balanced equation and the number of moles of NaOH to find the moles of H₂SO₄ needed.
• What is the volume of sulfuric acid needed if 0.0500 mol of NaOH reacts with it?


  Volume of H₂SO₄ = $\frac{0.0250}{0.150} =$$0.167 \text{ dm}^3 \text{ or } 167 \text{ cm}^3$
• How do you calculate the volume of hydrochloric acid needed to neutralise sodium carbonate?


  Use the balanced equation and the number of moles of sodium carbonate to find the moles of HCl needed.
• If 100 cm³ of 0.095 mol dm⁻³ sodium carbonate solution was neutralised by hydrochloric acid, how do you find the volume of hydrochloric acid needed?


  Calculate the moles of sodium carbonate and use the balanced equation to find the moles of HCl needed.
• What is the concentration of sodium carbonate solution if 125.0 cm³ was neutralised by 22.60 cm³ of 0.100 mol dm⁻³ hydrochloric acid?


  Use the balanced equation to find the moles of HCl and then calculate the concentration of sodium carbonate.
• What are the steps to carry out a titration?


  1. Measure the volume of the alkali in a conical flask.
  2. Add a few drops of indicator.
  3. Fill a burette with the acid solution.
  4. Slowly add the acid to the alkali while swirling.
  5. Stop when the indicator shows a colour change.
  6. Record the volume of acid used.
• What are the key concepts in acid-alkali titrations?


  • Use of indicators to determine endpoint
  • Balanced equations to find mole ratios
  • Calculating concentrations and volumes based on titration results