Bausch & Lomb
SPECTRONIC 20
SPECTRONIC 20
Absorbance
- - -
A.U.
Wavelength
500
nm
Sample Compartment
Empty
0%T
WAVELENGTH (nm)
100%T
Instrument is OFF. Press POWER to start.
-
Power On — Press the POWER button on the instrument. Allow 15 min warm-up (simulated).
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Set Wavelength to 395 nm — Br₂ absorbs maximally near 395 nm. Use the ▲▼ buttons or type in the field.
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Zero with Blank — Insert a cuvette with DI water. Press "INSERT BLANK & ZERO". Display should read 0.000.
Insert Blank (DI Water)
Why 395 nm? Br₂ (orange-brown) has maximum absorbance ~395 nm. Acetone, HCl, and water are colorless — they do not absorb at this wavelength. Only Br₂ absorbs, so absorbance directly tracks [Br₂].
Select each standard below, insert it into the SPEC 20, then record the absorbance. Complete all 5 to generate the Beer's Law curve.
| Standard | [Br₂] (M) | Absorbance | Status |
|---|
Select a run. Mix the solution as shown, insert into SPEC 20, then press Play to begin data collection.
00:00
Speed
Beer's Law Parameters
Run the standard curve first to see results here.
Pseudo-Rate Constants (k')
| Run | k' (M s⁻¹) | Ratio vs Run 1 | Exponent |
|---|
Rate Constant k & Final Rate Law
Complete at least 2 kinetics runs to compute the rate law.