Chapter 9 - Calculations Used in Analytical Chemistry Flashcards
It is a method to measure how much a chemical substance absorbs light
Spectrophotometry
How does Spectrophotometry work?
It measure the intensity of light as the beam of light passes through sample solution
Basic principle of Spectrophotometry
Each compound absorbs or transmits light over a certain range of wavelength
Wavelength of visible light
~400 nm to ~700 nm
It is an unchanging measure of the quantity of matter
Mass (m)
It is the force of gravitational attraction between that matter and Earth
Weight (w)
A ______ _____ is always based on _____ so that the results will not depend on ______
- chemical analysis
- mass
- locality
It is a precision weights used to calibrate weighing instruments and ensure accurate measurements
Calibration Weights
Calibration weights is used to
calibrate weighing instruments and ensure accurate measurements
Four fundamental ways to express solution concentration
- Molar concentration
- Percent concentration
- Solution-diluent volume ratio
- p-functions
It is the number of moles of that species that is contained in 1 L of the solution
Molar concentration (cx)
Molar concentration (cx) formula
cx = nx/V
molar conc. = no. moles solute/volume of liters
Unit of molar concentration
molar (M)
Molar (M) dimensions
mol/L, or mol L ^ -1
Molar concentration is also the number of
millimoles of solute per milliliter of solution
Other way to express concentration
in terms of percent (parts per hundred)
Three common methods to express percent concentration
- weight percent (w/w) = weight solute/weight solution x 100%
- volume percent (w/w) = volume solute/volume solution x 100%
- weight/volume percent (w/v) = weight solute, g/volume solution, mL x 100%
has the advantage of being temperature independent
weight percent
For very ______ _____, ____ ___ ____ (ppm) is a convenient way to express concentration
- dilute solutions
- parts per million (ppm)
Cppm = mass of solute/mass of solution x 10^6 ppm
For even more dilute solutions, what is used to express concentration
perts per billion (ppb
Cppb = mass of solute/mass of solution x 10^9 ppb
The composition of a dilute solution is sometimes specified in terms of the
volume of a more concentrated solution and the volume of solvent used in diluting it
The volume of the former is separated from that of the latter by a _____
colon
Scientists frequently express the concentration of a species in terms of its _____, or _____
p-function, or p-value
It is the negative logarithm (to the base 10) of the molar concentration of that species
p-value
p-value is expressed as
pX = -log [X]
______ of a substance is its mass per unit volume (kg/L or g/mL)
Density
units of density
- kg/L
- g/mL
It is the ratio of its mass to the mass of an equal volume of water at 4°C (dimensionless)
Specific gravity
It is the quantitative relationship among the amounts of reacting chemical species
Stoichiometry
