PCC/PCD 101: Pharm. Analytical Chemistry I - Week 4
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Questions and Answers

What is the unit of Molarity?

  • Milliequivalent/L
  • Mole/L (correct)
  • Gram/L
  • Equivalent/L

1 M HCl solution contains 36.5 grams of HCl per liter of solution.

True (A)

What is the formula for calculating the number of equivalents of solute in normality?

N = Equivalents / VL

The equivalent weight of a diprotic acid is calculated as Eq.wt = Mwt / ______.

<p>2</p> Signup and view all the answers

Match the following substances with their equivalent weight for one liter of solution:

<p>HCl = 36.5g NaOH = 40g H2SO4 = 96g KOH = 56g</p> Signup and view all the answers

How can normality be expressed in relation to molarity?

<p>N = nM (B)</p> Signup and view all the answers

A strong monoprotic acid has an equivalent weight equal to its molecular weight.

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

What is the purpose of calculating equivalent weight (Eq.wt)?

<p>To determine the amount of substance needed for reactions requiring equivalents.</p> Signup and view all the answers

What is the weight/volume percentage for 10 g of AgNO3 in 100 mL of solution?

<p>10 % (D)</p> Signup and view all the answers

1 ppm is equivalent to 1 mg/L.

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

What is the molar ratio (R) when titrating H₂SO₄ with NaOH?

<p>1/2</p> Signup and view all the answers

The concentration of a solution is expressed as __ g of solute in 100 g of solution when using weight/weight percentage.

<p>37</p> Signup and view all the answers

Match the concentration expressions with their formulas:

<p>% w/w = wt of solute / wt of solution x 100 % % v/v = Volume of solute / volume of solution x 100 % % w/v = wt of solute(g) / volume of solution(mL) x 100% ppm = mg of solute / L of solution</p> Signup and view all the answers

What is the equivalent weight of H₂SO₄ in grams?

<p>96 g (D)</p> Signup and view all the answers

The equation N.VmL for the sample equals N.VmL for the titrant at the equivalence point.

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

How many mg are there in 1 ppm?

<p>1 mg</p> Signup and view all the answers

What does qualitative analysis determine?

<p>The identity of a substance in a sample (C)</p> Signup and view all the answers

The equivalence point in titration is the same as the end point.

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

What is the role of an indicator in volumetric analysis?

<p>To provide a visible change at or near the equivalence point.</p> Signup and view all the answers

The _____ is the standard solution added from the burette during titration.

<p>titrant</p> Signup and view all the answers

Match the following indicators to their color changes in different pH environments:

<p>Phenol Phthalein = Colorless in acidic or neutral, pink in basic Methyl orange = Red in acidic, yellow in basic</p> Signup and view all the answers

Which of the following is NOT a characteristic of an ideal standard solution for titration?

<p>Availability in large quantities (D)</p> Signup and view all the answers

The end point of a titration can be calculated exactly.

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

What is the process called that involves the slow addition of titrant from the burette to the sample solution?

<p>Titration</p> Signup and view all the answers

Which of the following is NOT a characteristic of a primary standard substance?

<p>Regularly changes concentration over time (C)</p> Signup and view all the answers

Sodium hydroxide is considered a primary standard solution.

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

What is the primary method of standardizing a secondary standard solution?

<p>Titration against a primary standard solution</p> Signup and view all the answers

The balanced chemical equation is essential for _____ during volumetric analysis.

<p>complete reactions</p> Signup and view all the answers

Match the following acids to their classification as primary standards:

<p>Benzoic acid = Primary standard Hydrochloric acid = Secondary standard Oxalic acid = Primary standard Sulfamic acid = Primary standard</p> Signup and view all the answers

Which of the following must be true at the equivalence point during a titration?

<p>Amount of analyte = Amount of titrant (B)</p> Signup and view all the answers

Secondary standard solutions can have their concentrations calculated from the weight of the solute and the volume of the solution.

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

Name one example of a primary standard used as a reducing agent.

<p>Sodium oxalate</p> Signup and view all the answers

Flashcards

Quantitative analysis

Determination of the amount of a substance in a sample.

Qualitative analysis

Determination of the type of substance in a sample.

Volumetric analysis

A quantitative analysis method that measures the volume of a standard solution (titrant) required to react completely with the analyte.

Titrant

A standard solution of known concentration used in volumetric analysis.

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Equivalence point

The point in a titration where the amount of titrant added is chemically equivalent to the amount of analyte.

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End point

The point in a titration where a physical change is observed, indicating the end of the reaction.

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Indicator

A substance added to the analyte solution to indicate the end point of a titration.

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Standard solution

A solution with a precisely known concentration used in titrations.

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Primary Standard Solution

A solution whose concentration can be determined precisely by direct weighing of a pure substance, which is then dissolved in a known volume of solvent.

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Secondary Standard Solution

A solution whose concentration is determined by titration against a primary standard solution or a previously standardized secondary standard solution.

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Primary Standard Substance

A substance that is very pure, stable, and reacts completely in a known stoichiometric reaction. It is used to prepare primary standard solutions.

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Standardization

The process of determining the exact concentration of a solution by reacting it with a known volume of a solution of known concentration.

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Complete Reaction

A chemical reaction that occurs completely, with all reactants being transformed into products. It is essential for accurate titration analysis.

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Molar Concentration (Molarity)

The number of moles of solute per liter of solution.

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Titration

A method used to determine the concentration of a solution by reacting it with a solution of known concentration.

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Molarity

A measurement of the concentration of a solution, expressed as the number of moles of solute per liter of solution.

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1 Molar (1 M) solution

The number of moles of solute dissolved in 1 liter of solution.

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Normality (N)

A measure of the concentration of a solution, expressed as the number of equivalents of a chemical species per liter of solution.

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Equivalent weight (Eq.wt)

Represents the amount of a substance that will react with or replace one mole of hydrogen ions (H+) in a chemical reaction.

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Equivalent weight formula: Eq.wt = Mwt / n

The ratio of molecular weight (Mwt) to the number of H+ ions released or consumed in a neutralization reaction (n).

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1 Normal (1 N) solution

A solution containing 1 equivalent of a substance dissolved in 1 liter of solvent.

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Normality = n x Molarity

The relationship between normality (N) and molarity (M).

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Number of equivalents

The number of moles of a substance multiplied by the number of H+ ions released or consumed in a reaction.

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Weight/Weight percent (% w/w)

A method of expressing concentration as a percentage of the weight of the solute to the weight of the solution.

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Volume/Volume percent (% v/v)

A method of expressing concentration as a percentage of the volume of the solute to the volume of the solution.

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Weight/Volume percent (% w/v)

A method of expressing concentration as a percentage of the weight of the solute to the volume of the solution.

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Parts per Million (ppm)

A method of expressing very low concentrations, often used for pollutants or trace amounts in water.

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Equivalence Point Volume

The volume of titrant needed to reach the equivalence point in a titration.

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Molar Ratio (R)

The ratio of moles of analyte to moles of titrant in a balanced chemical equation.

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Dilution Process

A process of diluting a concentrated solution to a lower desired concentration by adding more solvent.

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Study Notes

PCC/PCD 101: Pharm. Analytical Chemistry I - Lecture Week 4

  • Analytical Chemistry: Divided into quantitative and qualitative analysis
  • Quantitative Analysis: Determines the concentration (amount) of a substance in a sample. Examples include volumetric analysis (titrimetry).
  • Qualitative Analysis: Determines the identity (type) of a substance in a sample. Examples include identifying cations and anions.
  • Volumetric Analysis (Titrimetry): A type of quantitative analysis. Titrant (standard solution with known concentration) is added to analyte (sample with unknown concentration) until the equivalence point is reached. The addition of titrant is controlled using a burette, and the reaction takes place in a conical flask.
  • Titration: A process of slow and controlled addition of titrant into the sample until a complete reaction occurs
  • Equivalence Point: The theoretical point in titration where the amount of titrant is chemically equivalent to the amount of sample.
  • End Point: A practical point observed in titration using an indicator. The point where an observable physical change occurs , usually near the equivalence point, indicating the completion of the reaction.
  • Titration Error: Difference between the end point and equivalence point.
  • Indicator: A substance added to the analyte to make the end point easily observable. Indicators change color at or near the equivalence point.
  • Typical Indicator Changes: Indicators may change in color(or appearance of turbidity)
    • Examples: Phenolpthalein, Methyl Orange
  • Standard Solutions: Solutions with precisely known concentrations used for titrations. They are classified as primary or secondary.
  • Primary Standard Solution: Prepared by dissolving a known amount of a primary standard substance in a measured volume of water. Concentration does not change over time (e.g., Benzoic acid, Potassium Acid Phthalate).
  • Characteristics of Primary Standard Substances: Must be very pure, stable, High molecular weight, easily available, soluble in titration medium
  • Secondary Standard Solution: Solutions whose concentrations cannot be calculated directly from the weight. Their concentrations must regularly determined via process called standardization. Standardization can be done by titration with a primary standard or another standardized secondary standard solution (eg: HCl, NaOH)
    • Characteristics of ideal standard solutions for titration:
      • Concentration must be stable over long time
      • Reaction with analyte must be rapid
      • Undergo selective simple reaction
      • Demonstrated with a simple balanced chemical equation
  • Requirements for Reactions in Volumetric Analysis:
    • Simple single reaction with balanced chemical equation
    • Complete and quantitative reaction between analyte and titrant
    • Be rapid to allow sharp end points
    • Have suitable method for end point detection
  • Molar Concentration (Molarity): Number of moles of solute in one liter of solution. M = moles/volume (L).
  • Calculating Molarity: M = wt/M.wt (gram) x (1/Volume(L)).
  • Preparation of 1 Molar solution: Dissolves one mole (MWt) of a substance in 1L of water
  • Normal Concentration (Normality): Number of equivalents of solute in one liter of solution. N = equivalents/volume(L).
  • Equivalent Weight (Eq.wt): Molar weight divided by the number of H+ released/consumed in the reaction. Eq. wt. = M. wt / n where n = number of H+, it differs based on reaction type.
  • Preparation of 1 Normal (1N) solution: Dissolves 1 equivalent weight of a substance in 1L of water
  • Percent Concentration: A way to express concentration in terms of percentage: weight/weight, volume/volume, weight/volume e.g., 10% AgNO3 = 10g AgNO3 in 100mL solution.
  • Parts per Million (ppm): Used for very low concentrations, 1 ppm = 1 mg/L = 1µg/mL = 1 ng/µL.
  • Dilution Process: C₁V₁ = C₂V₂ (Concentration before dilution x Volume before dilution = Concentration after dilution x Volume after dilution).
  • Important Conversions between different concentration units.

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This quiz covers key concepts from Week 4 of Pharm. Analytical Chemistry I. Focus areas include qualitative and quantitative analysis, volumetric analysis, and the process of titration. Test your understanding of the fundamental techniques and principles used in analytical chemistry.

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