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Questions and Answers
What is the purpose of washing the last traces of solute from the watch-glass into the beaker during the preparation of a standard solution?
What is the purpose of washing the last traces of solute from the watch-glass into the beaker during the preparation of a standard solution?
- To prevent the formation of crystals in the solution
- To ensure that all the solute is dissolved in the solution
- To ensure that the solute is evenly distributed in the solution
- To ensure that the correct amount of solute is used (correct)
Why is it important to clean the watch-glass and spatula before use in the preparation of a standard solution?
Why is it important to clean the watch-glass and spatula before use in the preparation of a standard solution?
- To ensure that the correct amount of solute is used
- To ensure that the solute dissolves evenly in the solution
- To prevent the loss of solute during the weighing process
- To prevent contamination of the solution with other substances (correct)
Which of the following compounds would be unsuitable for preparing a standard solution because it is hygroscopic?
Which of the following compounds would be unsuitable for preparing a standard solution because it is hygroscopic?
- Potassium hydroxide
- Sodium hydroxide (correct)
- Concentrated hydrochloric acid
- Sodium carbonate
What is the purpose of using a volumetric pipette when preparing a standard solution?
What is the purpose of using a volumetric pipette when preparing a standard solution?
What is the purpose of washing the conical flask with distilled water only before performing a titration?
What is the purpose of washing the conical flask with distilled water only before performing a titration?
Why is it important to wash the graduated or volumetric pipette with distilled water followed by the solution it will contain before performing a titration?
Why is it important to wash the graduated or volumetric pipette with distilled water followed by the solution it will contain before performing a titration?
What precaution should be taken when preparing a standard solution of concentrated hydrochloric acid?
What precaution should be taken when preparing a standard solution of concentrated hydrochloric acid?
What is the purpose of using a teat pipette to add phenolphthalein indicator to the sodium carbonate solution during a titration?
What is the purpose of using a teat pipette to add phenolphthalein indicator to the sodium carbonate solution during a titration?
What is the purpose of the rough titration (Step 4)?
What is the purpose of the rough titration (Step 4)?
What is the purpose of using a dark or clear background while reading the burette scale?
What is the purpose of using a dark or clear background while reading the burette scale?
What is the reason for repeating the titration multiple times (Step 5)?
What is the reason for repeating the titration multiple times (Step 5)?
What is the primary aim of titration in this experiment?
What is the primary aim of titration in this experiment?
What is the reason for adding the hydrochloric acid dropwise in the final titration (Step 5)?
What is the reason for adding the hydrochloric acid dropwise in the final titration (Step 5)?
Why is the rough titre value not included in the calculation of the average titre value?
Why is the rough titre value not included in the calculation of the average titre value?
What is the correct formula for calculating the titre value?
What is the correct formula for calculating the titre value?
What is the purpose of touching the inner wall of the conical flask to the burette tip after delivering the hydrochloric acid (Step 5)?
What is the purpose of touching the inner wall of the conical flask to the burette tip after delivering the hydrochloric acid (Step 5)?
What is the concentration of a solution containing 3 moles of sodium chloride (NaCl) dissolved in 500 mL of water?
What is the concentration of a solution containing 3 moles of sodium chloride (NaCl) dissolved in 500 mL of water?
You have a 2.5 M solution of potassium hydroxide (KOH). What volume of this solution would you need to obtain 0.125 moles of KOH?
You have a 2.5 M solution of potassium hydroxide (KOH). What volume of this solution would you need to obtain 0.125 moles of KOH?
A 25.00 mL sample of hydrochloric acid (HCl) is titrated with 0.150 M sodium hydroxide (NaOH). The titration requires 32.50 mL of NaOH solution to reach the endpoint. What is the concentration of the HCl solution?
A 25.00 mL sample of hydrochloric acid (HCl) is titrated with 0.150 M sodium hydroxide (NaOH). The titration requires 32.50 mL of NaOH solution to reach the endpoint. What is the concentration of the HCl solution?
What is the molar mass of sulfuric acid (H2SO4)?
What is the molar mass of sulfuric acid (H2SO4)?
A standard solution is prepared by dissolving a known mass of solute in a known volume of solvent. What is the primary reason for using distilled water as the solvent in preparing standard solutions?
A standard solution is prepared by dissolving a known mass of solute in a known volume of solvent. What is the primary reason for using distilled water as the solvent in preparing standard solutions?
In volumetric analysis, why is it important to use a burette to deliver the titrant?
In volumetric analysis, why is it important to use a burette to deliver the titrant?
Which of the following correctly describes the process of titration?
Which of the following correctly describes the process of titration?
Which of the following is NOT a common use of volumetric analysis?
Which of the following is NOT a common use of volumetric analysis?
Flashcards
Volumetric Analysis
Volumetric Analysis
A quantitative analysis method determining substance volume for concentration.
Concentration
Concentration
The amount of solute (moles) in a liter of solution.
Molarity (M)
Molarity (M)
A measure of concentration defined as moles of solute per liter of solution.
Standard Solution
Standard Solution
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Titration
Titration
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Steps for Preparing Standard Solution
Steps for Preparing Standard Solution
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Calculating Concentration
Calculating Concentration
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Acid/Base Reaction in Titration
Acid/Base Reaction in Titration
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Deliquescent Compounds
Deliquescent Compounds
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Hygroscopic Compounds
Hygroscopic Compounds
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Number of Moles
Number of Moles
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Relative Formula Mass (RFM)
Relative Formula Mass (RFM)
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Phenolphthalein
Phenolphthalein
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Precautions in Titration
Precautions in Titration
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Burette Usage
Burette Usage
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Meniscus Reading
Meniscus Reading
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Initial Volume
Initial Volume
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Concordant Titre Values
Concordant Titre Values
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Rough Titre Value
Rough Titre Value
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Final Volume Measurement
Final Volume Measurement
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Dropwise Addition
Dropwise Addition
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Concentration Calculation
Concentration Calculation
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Study Notes
Volumetric Analysis
- Volumetric analysis determines the amount of a substance by its volume
- It's a branch of quantitative analysis
- Titration is a procedure used in volumetric analysis to determine the concentration of a solution
- Common in acid-base reactions
Concentration
- Concentration of a solute in a solution is the number of moles of solute present in 1 liter of solution
- 1 Liter = 1000 cm³ = 1 dm³
- Concentration (Moles/L) or Molarity (M) = Amount of solute (Moles) / Volume of solution (Litres)
- Molarity = Moles / Volume
Worked Examples (Page 1)
-
Example 1: Find the concentration of hydrochloric acid (HCl) if 2 moles of HCl gas are dissolved in 4 dm³ of water.
- Concentration = 0.5 mol dm⁻³
-
Example 2: Calculate the moles of sulfuric acid (H₂SO₄) in 50 dm³ of a 0.5 mol dm⁻³ solution.
- Moles = 25 moles
-
Example 3: Find the volume of 0.1 mol dm⁻³ sodium hydroxide (NaOH) solution needed for 0.03 moles of NaOH.
- Volume = 0.3 dm³
-
Example 4: Calculate the concentration (mol dm⁻³) of a sodium carbonate (Na₂CO₃) solution made by dissolving 212 g of Na₂CO₃ in 2 dm³ of water.
- RFM of Na₂CO₃ = 106 g/mol
- Concentration = 1.0 mol dm⁻³
Standard Solutions
- A standard solution has a known concentration of solute
- Prepared using pure solute and distilled water
Laboratory Preparation of a Standard Solution (Page 4)
- Stage 1: Weigh accurately, transfer to beaker, dissolve in solvent
- Stage 2: Ensure all solid dissolves
- Stage 3: Transfer quantitatively to volumetric flask - wash beaker and transfer washings
- Stage 4: Add solvent until the bottom of the meniscus touches the calibration mark
- Stage 5: Stopper and shake to mix thoroughly
Precautions (Page 4)
- Clean glassware before use
- Wash solute from watch-glass to beaker
- Use distilled water (for quantitative transfer)
Worked Example (Page 5)
- Calculate the mass of sodium carbonate needed to prepare 250 mL of a 0.05 mol/L solution
- Steps:
- Calculate moles by concentration * volume (0.0125 mol)
- Use RFM of Na₂CO₃ (106 g/mol) to convert moles to grams (1.33 g Na₂CO₃)
Titration
- Used in acid-base neutralisation reactions
- Two main purposes:
- Preparation of soluble salts
- Determining the unknown concentration of an acid or base
- Standard solution is reacted with a solution of unknown concentration
Choice of Indicator (Page 6)
- Indicators show the end-point of a reaction
- Change color at endpoint
- Different Indicators are for different solutions (strong acid - strong base, etc.)
Titration Procedure (Page 6)
- Precautions (Step 1): Wash graduated/volumetric pipettes and conical flasks with distilled water and the appropriate solution (e.g., solution in the conical flask for pipette)
Step 1, 2, 3, 4, 5, & 6 (Pages 7-8)
- Detailed steps explaining how to perform a titration, including the use of a burette, volumetric flask, pipette, and pipette filler, and how to add the indicator and read the appropriate measurements.
Overview of Titration (Page 9)
- Visual steps that explain how to run a titration experiment from start to finish.
Worked Example (Page 10)
- In a titration of 25 cm³ of 0.100 mol/dm³ sodium hydroxide solution by 20cm³ of a solution of hydrochloric acid
- Steps:
- Calculate the moles of sodium hydroxide solution
- Moles of sodium hydroxide = concentration * volume = 0.0025 mol
- Mole ratio is 1:1, so moles of Hydrochloric acid are 0.0025 mol
- Calculate concentration: 0.0025mol / 0.0200 dm³ = 0.125 mol/dm³
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