Analytical Chemistry: Qualitative vs Quantitative Analysis

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Questions and Answers

What is Qualitative Analysis?

  • None of the above
  • Both A and B
  • Determination of the chemical identity of the species in the sample. (correct)
  • Determination of the amount of species or analytes, in numerical terms.

In order to perform quantitative analysis, complete qualitative analysis is needed.

True (A)

Which of the following is a method of Quantitative Analysis?

  • Volumetric method
  • Gravimetric Method
  • Instrumental Method
  • All of the above (correct)

What is the purpose of a standard solution?

<p>A standard solution is a reagent of exactly known composition used in a titration.</p> Signup and view all the answers

What is a primary standard?

<p>A primary standard is a highly purified chemical compound.</p> Signup and view all the answers

What does standardization in chemistry refer to?

<p>Standardization is the process whereby the concentration of a standard solution is determined by titrating with a primary standard solution.</p> Signup and view all the answers

What are the requirements of a primary standard?

  1. Highest purity.
  2. Stable and not attacked by atmosphere.
  3. Not be hygroscopic.
  4. Available and not expensive.
  5. High equivalent to minimize weighing errors.

<p>1, 2, 3, 4, 5 (C)</p> Signup and view all the answers

What is normality in terms of concentration units?

<p>Normality is the number of equivalent weights contained in one liter of solution.</p> Signup and view all the answers

How do you calculate normality?

<p>Normality = (wt/equivalent weights) / volume of solution (L)</p> Signup and view all the answers

What is an equivalent weight of an acid?

<p>An equivalent weight of an acid is (gram molecular weight) / (no. of (H)atoms that can be replaced)</p> Signup and view all the answers

What is molarity?

<p>Molarity is the number of gram molecular weights or the number of moles of solute in one liter of solution.</p> Signup and view all the answers

How do you calculate moles of solute?

<p>Moles of solute = (weight) / (gram molecular weight)</p> Signup and view all the answers

How do you calculate the normality of concentrated acid?

<p>Normality = (m.wt x % × sp.g) / 1000</p> Signup and view all the answers

How do you prepare an acid from concentrated acid?

<p>N₁V₁ = N2V2</p> Signup and view all the answers

The solution must be prepared in such a way that it is concentration is known to high degree of precision for many experiment.

<p>True (A)</p> Signup and view all the answers

What is the purpose of the experiment "Preparation of standard solution from a solid"?

<p>The purpose of this experiment is to give you practice at the techniques involved in the preparation of such a solution.</p> Signup and view all the answers

What kind of solution will be prepared in Experiment 1?

<p>A 100 ml of 0.1 mol/ L Sodium chloride solution</p> Signup and view all the answers

Which of the following materials are NOT required for Experiment 1?

<p>Weighing boat (B)</p> Signup and view all the answers

What is the first step in the procedure for Experiment 1?

<p>Calculation the mass of solute required.</p> Signup and view all the answers

Why is it important to properly tare the balance before adding solute to the beaker in Experiment 1?

<p>To ensure an accurate measurement of the solute's mass.</p> Signup and view all the answers

What is the purpose of transferring the solution from the beaker to the volumetric flask?

<p>To transfer the solution into a clean volumetric flask.</p> Signup and view all the answers

Why should the rod and beaker be rinsed into the flask when transferring the solution?

<p>To ensure that all the solute is transferred into the volumetric flask.</p> Signup and view all the answers

What do you do if the water is approximately 1cm below the etched mark on the neck of the volumetric flask?

<p>Add distilled water until the water is approximately 1cm below the etched mark on the neck of the volumetric flask.</p> Signup and view all the answers

What is the final step in the preparation of the standard solution?

<p>Place the stopper on the volumetric flask and mix the solution thoroughly by inverting and shaking the flask.</p> Signup and view all the answers

It is okay to add water to a level above the line on the neck of the flask.

<p>False (B)</p> Signup and view all the answers

What is the purpose of inverting the volumetric flask?

<p>To mix the solution thoroughly by inverting and shaking the flask.</p> Signup and view all the answers

Why should the final solution be left stoppered?

<p>To prevent evaporation and ensure that the concentration remains constant.</p> Signup and view all the answers

Explain why filling the flask above the line would change the concentration of the solution?

<p>If we filled the flask to above the line how would this have changed the concentration of the solution?</p> Signup and view all the answers

Flashcards

Qualitative Analysis

Determination of the chemical identity of species in a sample.

Quantitative Analysis

Determination of the amount of species in numerical terms.

Volumetric Method

A method that measures volume to determine sample amount.

Gravimetric Method

A method that involves measuring mass to analyze samples.

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Instrumental Method

Uses instruments like spectrophotometers to measure sample amounts.

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Standard Solution

A reagent of exactly known composition used in titration.

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Primary Standard

A highly purified chemical compound used for standardization.

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Standardization

Process of determining the concentration of a standard solution.

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Normality

Number of equivalent weights in one liter of solution.

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Equivalent Weight of an Acid

Gram molecular weight divided by the number of replaceable hydrogen atoms.

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Equivalent Weight of a Base

Gram molecular weight divided by the number of replaceable hydroxyl groups.

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Molarity

Moles of solute in one liter of solution.

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Formality

The number of gram formula weights per liter of solution.

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Preparation of Standard Solution

Creating a solution with a precise known concentration.

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Sodium Chloride Solution

A common standard solution prepared for titration experiments.

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Balance

Instrument used to measure the mass of the solute accurately.

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Volumetric Flask

A glass vessel used to prepare standard solutions.

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Titrate

Process of adding a solution to determine concentration.

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Concentration Calculation

Determining the concentration of a prepared solution.

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Inversion of Volumetric Flask

Mixing the solution by inverting the flask for homogeneous distribution.

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Stoppering

Closing the volumetric flask to prevent contamination.

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Meniscus

The curve at the liquid's surface in a container.

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Dilution

The process of reducing the concentration of a solution.

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Concentrated Acid Normality Calculation

Formula to calculate normality of concentrated acids.

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V1N1 = V2N2

Equation Used for dilution of solutions.

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Reactivity

The capacity of a species to engage in a chemical reaction.

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Epistemology in Qualitative Research

Study of knowledge related to qualitative data collection.

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Generalization in Research

Applying findings broadly rather than to specific cases.

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Non-Numeric Techniques

Methods in qualitative analysis that do not rely on numbers.

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Study Notes

Analytical Chemistry

  • Qualitative Analysis involves identifying the chemical components in a sample.
  • Quantitative Analysis determines the amount of specific components in a sample.
  • Quantitative analysis requires a complete qualitative analysis first.
  • Quantitative Methods:
    • Volumetric Method: Measures the volume of a solution to determine the amount of a sample
    • Gravimetric Method: Measures the mass of a substance to determine the amount of a sample.
    • Instrumental Method: Uses instruments like spectrophotometers to determine the amount of a sample
  • Qualitative Methods:
    • Focus on non-empirical proofs
    • Interpret concepts, meanings, and relationships.
    • Avoid numerical data reduction.

Quantitative Analysis Definitions and Terms

  • Standard Solution: A solution with a precise, known composition used in titrations.
  • Primary Standard: A highly pure chemical compound used to standardize a solution.
  • Standardization: A process to determine the exact concentration of a standard solution using a primary standard.

Requirements of a Primary Standard

  • High purity
  • Stable and unaffected by the atmosphere
  • Non-hygroscopic
  • Readily available and affordable
  • High equivalent weight to minimize weighing errors

Concentration Units

  • Normality: The number of equivalent weights of solute in one liter of solution. Normality = (wt/equivalent weights)/volume of solution (L)
  • Equivalent weight of an Acid: (gram molecular weight)/(number of H atoms that can be replaced)
  • Equivalent weight of a Base: (gram molecular weight)/(number of OH groups that can be replaced)
  • Molarity: The number of moles of solute in one liter of solution. Molarity = (moles of solute)/(volume of solution (L))
  • Formality: The number of gram formula weights per liter of solution.
  • To calculate the Normality of concentrated acid: Normality = (m.wt x % x sp.g)/1000

Experiment (Preparation of a Standard Solution)

  • Introduction: Solutions of known concentrations are crucial for various experiments. This lab demonstrates preparing accurately concentrated solutions.
  • Purpose: To prepare 0.1 mol/L sodium chloride solution accurately.
  • Materials: Balance, sodium chloride, distilled water, 100 mL volumetric flask, funnel, spatula, 150 mL beaker, dropper, wash bottle
  • Procedure:
    1. Calculate the mass of sodium chloride required for the solution.
    2. Weigh sodium chloride on the balance.
    3. Add water to dissolve salt using a beaker.
    4. Transfer solution from the beaker to the volumetric flask. Rinse beaker thoroughly.
    5. Add distilled water up to the specified line to achieve the precise volume in the volumetric flask. Important: do not exceed the etched mark. Use a dropper to precisely reach the mark.
    6. Mix the solution by inverting the flask several times.
  • Analysis: Calculate the concentration of the prepared solution and explore reasons for using volumetric flasks and stopper.

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