✅ ORGANIZATION OF THE VIDEO ???? 0:00: Presentation ???? 0:55: Introduction ???? 1:21: Objectives ???? 1:33: I) Operating principle ???? 3:05: Operation of a spectrophotometer ???? 4:00: White adjustment ???? 4:45: Transmittance and absorbance ???? 6:27: Two types of spectrophotometers ???? 7:15: II) Plotting the absorption spectrum ???? 8:10: Precautions when filling the tank ???? 9:03: Production and interpretation of the absorption spectrum ???? 11:20: Measurement at fixed wavelength ???? 12:40: III) Relationship between absorbance and concentration of absorbing species ???? 13:35: Scope of validity ???? 14:15: Conclusion ✅ OTHER USEFUL VIDEOS ???? Dissolution & dilution: • ???? Dissolution & dilution (with @myMax... ???? Spectrophotometric dosage by calibration: • ???? Spectrophotometric dosage by eta... ✅ DISCOVER MAXICOURS This video was produced with the support of Educlever, publisher of teaching platforms such as Maxicours, the online tutoring site for students from CP to terminale. To revise at home, in all subjects, more than 100,000 course sheets, interactive exercises, videos and assessments await you! And an Online Teachers service allows you to get help from teachers from the National Education system. ???? To discover Maxicours offers: https://www.maxicours.com/se/blablareau/. ✌️✌️✌️ FIND BLABLAREAU ✌️✌️✌️ ✅ Website: https://blablareau-chimie.fr/ ✅ Social networks: ???? Instagram: blablareau_au_labo ???? Facebook: / blablareauaulabo ???? Twitter: @Blablareau ✅ SUPPORT the creation of videos: ???? Tipeee: https://en.tipeee.com/blablareau-au-labo ???? U-tip: https://www.utip.io/feed/blablareauau... ✅ Secondary channel intended for higher education students: ???? / @blablareauautableau ???????????? THANKS ???????????? ???? Delay Lama : / @zionco6726 ✅ ADDITIONAL INFORMATION ???? Accuracy of absorbance measurements – Absorbance values ​​(at 5:45) The best measurement accuracy is obtained when the absorbance is between 0.1 and 2: An absorbance measurement has an accuracy of the order of a few thousandths. This accuracy varies depending on the quality of the spectrophotometer and the cuvettes, the purity of the solvent, the homogeneity of the solution, etc. Thus, when the absorbance is less than 0.1, a few thousandths have a significant relative importance in the measurement, and the relative accuracy of the measurement becomes poor. The spectrophotometer detector records the ratio between the reference light intensity and that of the sample: when the absorbance is greater than 2, the sample flux is less than 1% of the reference flux, i.e. out of 100 photons emitted, the detector does not even capture 1. In this case, the accuracy of the detector becomes significant in measuring the light flux, which results in significant variations in the absorbance value. In practice, remember that we will have reasonable measurements for absorbances lower than 2. ???? Choice of the study wavelength (at 11:25) When we want to use the Beer-Lambert law to determine concentrations from absorbance measurements, the chosen wavelength is generally the wavelength λmax of the absorption maximum, and this for two reasons: First, it is at the wavelength λmax that the sensitivity of the measurements is the best (the sensitivity is (dA/dC = ε(λ)·ℓ): small variations in concentration can be detected because they lead to large variations in absorbance. Second, it is at the wavelength λmax that the width Δλ of the quasi-monochromatic beam has the least influence: when dA/dλ = 0, a slight variation in λ practically does not vary A, the uncertainty on the measurement is thus minimized.