chem lab (analysis1) Flashcards
what is chemical analysis
the determination of the
-identity of the chemical substance(qualitative)
-amount of a particular substance (quantitative)
2 types of chemical analysis and their definition
- clinical analysis/non-instrumental analysis is a group of analytical methods the only requires chemicals, balance, calibrated glassware, and other common laboratory apparatus. An instance is the TITRATION.
- instrumental analysis uses an analytical instrument in chemical analysis to determine the identity or amount of the analyte. An instance is BEER’S LAW
what is an analytical instruments?
devices that measure a
physical or chemical property of the analyte
3 major categories of instrumental analysis
- Spectroscopic methods (Spectroscopy)
- Electroanalytical methods
- Separative methods
what is electromagnetic spectrum?
term used by scientist to describe the entire
range of light in the universe. The spectrum ranges from radio waves to gamma
rays.
in what ways can light be described?
in terms of frequency, hertz (Hz) and wavelength
hertz
measures the frequency or the number of waves that pass by a point in
one second
wavelength
measures the distance from the peak if one wave to the peak of
the next
what does it means when the hertz and wavelength become inversely related to each other?
the larger the
frequency, the smaller the wavelength
spectroscopy
-study of the interaction of energy with radiated
matter
-an area of science that is concerned with absorption, emission, and
scattering of electromagnetic radiation by atoms and molecules.
(Hanson, et. al., n.d.)
spectrometry
the measurement of the interactions between light
and matter. Also includes the reactions and measurements of radiation
intensity and wavelength.
spectrophotometry
method used to measure how much a chemical
substance absorbs light by measuring the intensity of light, when a
beam of light passes through the sample solution
what is the basic principle of spectrophotometry
each
compound absorbs, transmits, or reflects light (light as in
electromagnetic radiation) over a certain wavelength. The
absorb light or transmitted light is then measured which is
unique for every chemical substance.
spectrophotometer
the instrument used to measure
the intensity of light absorbed after it passes through the
sample solution.
colorimetry
-one of the earliest spectroscopic
in year 1856, early colorimetric analysis is the Nessler’s method for?
ammonia
what does nessler’s method uses and involve
- Nessler’s method uses visual comparison between
the colour produced by an unknown amount of a
substance in sample solution with the same colour
produced by a known amount of the same substance
in standard solutions. - Nessler’s method involves preparation of standard
solutions with varying concentrations. - the colour of the sample solution that approximately
matches the colour of one of the prepared standards is
the concentration of the unknown solution.
Modern day colorimetric methods no longer use Nessler’s
tube but colorimeters. TRUE OF FALSE?
true
colorimeters
-used to determine the concentration of
substances that absorb light in the visible region (wavelength
= 400 – 800 nm).
-light-sensitive device measuring the transmittance and
absorbance of light passing through a liquid sample.
-only applicable to colored solutions.
-Designed to perform a psychophysical sample analysis or
measurements correlate to the human perception.
the principle of colorimeter is based on?
Beer – Lambert’s
Law
The Beer-lambert law states that
“there is a linear
relationship between the concertation and the
absorbance of the solution, which enables the
concentration of a solution to be calculated by
measuring its absorbance”.
The absorbance depends on two external assumptions: namely?
- The absorbance is directly proportional to the
concentration (c) of the solution of the sample used
in the experiment. - The absorbance is directly proportional to the length
of the light path (l) which is equal to the width of the
cuvette.
