Chemical Kinetics

In this experiment you will find the rate law and rate constant of a chemical reaction.

Experimental Setup

Spectrophotometer

Experimental setup for the kinetics spectrophotometer experiment

Figure 1: The complete experimental setup for the kinetics measurement.

Top view of the experimental setup showing the optical arrangement

Figure 2: Top view of the setup showing the optical path and components.

Optical Setup & Spectrometer

The spectrophotometer setup (Figure 1) now includes the following components, in light path order:

  1. Light source: Halogen lamp, model GY6.35-HB-50W, powered by a stabilized power supply and an in-line intensity dimmer to set the lamp brightness precisely.
  2. Beam conditioning optics: A set of lenses to collimate the lamp output and then focus it. An optical fiber collects the conditioned light after the first lens to create an effective point source. A second lens focuses this point source onto a pinhole to define the beam.
  3. Cuvette holder: The collimated beam emerging from the pinhole passes through a standard 10 mm cuvette containing the sample.
  4. Collection fiber: A second optical fiber placed after the cuvette captures the transmitted light and delivers it to the spectrometer.
  5. Spectrometer: Avantes AvaSpec-VRS2048CL-EVO (see specifications below).

Spectrometer Used in the Laboratory

Model: Avantes AvaSpec-VRS2048CL-EVO

The AvaSpec-VRS2048CL-EVO is a fiber-optic, modular dispersive array spectrometer. Light from the collection fiber enters through an entrance slit, is collimated, dispersed by a diffraction grating, and focused onto a 2048-pixel linear CCD detector. Each pixel measures a narrow wavelength band, so the instrument records a full spectrum in fractions of a second with no moving parts—ideal for fast, time-resolved measurements.

Key Specifications
  • Detector: 2048-pixel CCD (EVO electronics)
  • Spectral range: typically 200–1100 nm (depends on selected grating/slit)
  • Optical resolution: ~0.2–2.0 nm (grating & slit dependent)
  • Integration time: ~20 µs to 10 s
  • Interface: USB 3.0 / Ethernet
  • A/D converter: 16-bit; high SNR and dynamic range (model dependent)
  • Software: AvaSoft 8 (Scope, Absorbance/Transmittance, Spectrum-3D, etc.)

Manufacturer page: Avantes – AvaSpec-VRS2048CL-EVO specifications