1.3: Beer's Law - Data and Report

General Chemistry II Lab Manual · LibreTexts

0%

Contents

    Text

    Size
    100%
    Theme
    Typeface
    Line length
    Spacing

    From LibreTexts, under CC BY 4.0, as the source states it; its equations are written in TeX, which the PDF shows typeset. This page at LibreTexts.

    Name: ____________________ Partner(s): ____________________ Date: ____________________

    DATA AND OBSERVATIONS

    Unknown ID: __________

    Wavelength of Maximum Absorbance (\(\lambda_{\text{max}}\)): __________ nm

    Table \(\PageIndex{1}\): Standard Solutions Absorbance Data
    Test Tube Concentration (M) Absorbance
    1 0.020 __________
    2 0.040 __________
    3 0.060 __________
    4 0.080 __________
    5 0.100 __________
    Table \(\PageIndex{2}\): Beer's Law Regression Parameters and Unknown Analysis
    Parameter Value
    Slope, m (M−1) __________
    Y-intercept, b __________
    Correlation coefficient, r __________
    Unknown Absorbance __________
    Calculated Unknown Concentration (M) __________

    Attach an image of the full absorbance spectrum for the standard solution:

    __________
     
     
     
     

    Attach an image of the Beer’s Law Plot (\(A\) vs. Concentration):

    __________
     
     
     
     

    POST-LAB QUESTIONS

    1. Explain why it is critical to measure the absorbance of standard and unknown solutions at \(\lambda_{\text{max}}\) rather than at an arbitrary wavelength. What physical advantage does measuring at \(\lambda_{\text{max}}\) provide when determining unknown concentration?

      __________
       
       

    2. Evaluating regression statistics:

      A student obtains a low correlation coefficient (\(r = 0.85\)) or a large y-intercept (\(b = 0.10\)) on their Beer's Law calibration plot.

      DATA ANALYSIS HINT

      Consider the physical source of error:

      • A low \(r\) value indicates random error (e.g., inconsistent pipetting volume).
      • A high y-intercept (\(b\)) indicates systematic error (e.g., dirty blank, fingerprint on cuvette, or uncalibrated instrument).

      Explain specifically what experimental mistakes would cause each of these statistical outcomes.

      __________
       
       
       
       

    3. Select two cuvette handling guidelines (wiping with Kimwipes, handling by ribbed sides only, dislodging bubbles, or orienting clear sides along light path) and detail how ignoring them would alter your absorbance readings and calculated unknown concentration.

      __________
       
       

    This page titled 1.3: Beer's Law - Data and Report was last modified on Thu, 03 Sep 2026 15:06:17 GMT and is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Vince Hradil.