Liquids And Solutions Flashcards
What does an autopipette allow?
Small volumes of liquid to be measured very accurately
Describe how an autopipette work?
The plunger at the top of an autopipette has two stops. To draw liquid into the autopipette, the plunger is pressed down to the first stop, the tip is placed just under the surface of the liquid and the plunger is released. The tip is then placed against the side of the tube and the plunger is pressed down
What are burettes used to do?
Dispense precise volumes of liquid reagents
Describe how you would use a burette?
It is rinsed with the solution to be used by filling it, then opening the tap at the bottom and allowing the solution to run through. The tap is closed and the burette is filled just above the 0cm3 mark with the required solution. The tap is then slowly opened and the solution is run down to the 0cm3. The tap is closed and the burette is ready for use.
When measuring from a burette what is it important to do?
Take readings from the bottom of the meniscus
What does dilution involve?
Reducing the concentration of a substance in a solution
What is repeated dilution from a stock solution known as?
A serial dilution
What can be quantified using a colorimeter?
The concentration of a pigmented compound
What does a colorimeter measure?
the absorbance of specific wavelengths of light by a solution.
How does a colorimeter work?
A colorimeter works by passing a light beam, at a specific wavelength, through a cuvette containing a sample solution.
Some of the light is absorbed by the sample; therefore, light of a lower intensity hits the detector and the machine will display an absorbance value.
How do you calibrate a colorimeter?
a cuvette containing calibration solution (usually distilled water) is placed in the cuvette compartment and the calibrate button is pressed.
This will provide the user with a reading of 0 absorbance.
The user can then place a cuvette containing a sample solution into the cuvette compartment and take a reading of the absorbance of the sample by pressing the test button.
Name one method that is used to determine the concentration of a solution.
A standard curve
What can a standard curve be used to do?
determine the concentration of an unknown sample.
Name another method used to determine the concentration of an unknown solution
a titration.
Describe how a titration is carried out
using a burette to deliver a solution of known volume and concentration to a solution of unknown concentration underneath.
The volume and concentration of the known solution along with the stoichiometry of the reaction are used to calculate the concentration of the unknown solution.
