Ch 21 - (Experimental Design and Separation Techniques) Flashcards
How can time be measured?
Stopwatch or stop clock to one or two decimal places
What are the units of time?
Seconds or minutes
How is temperature measured?
- Thermometer or digital probe
- laboratory thermometers have a precision of half or 1 degree
What are the units of temperature?
degree Celsius (°C)
How is mass measured?
Digital balance (2 decimal places)
What is the standard unit of mass?
kg or g
What is used to measure volume of liquids?
- Volumetric pipette (fixed volume; 10 - 25cm^3)
- Measuring or graduated cylinder (approx volume)
- Burette ( variable of volume; 0 - 50 cm^3)
What are advantages of temperature probe versus thermometer?
- more precise readings
- easily take multiple readings
- use automatic sampling over longer periods of time
What are disadvantages of temperature probe versus thermometer?
- probe can be corroded by some reagents
- probes more expensive to replace
What is the advantage of volumetric pipette versus a measuring cylinder?
Pipette measures very acutely
What is the disadvantage of volumetric pipette versus a measuring cylinder?
harder to sue and only measures one fixed volume
What is the advantage of gas syringe versus inverted cylinder for collecting gases?
gas syringe are easy to set up and keep the gas dry
What is the disadvantage of gas syringe versus inverted cylinder for collecting gases?
- piston can stick
- limited volume can be connected
- delicate and expensive
What is the advantage of microscale versus normal scale quantities?
- less wasteful of regents
- saves energy
- safer
What is the disadvantage of microscale versus normal scale quantities?
- hard to see what’s happening
- loses a lot of materials in separating and purifying products
What does solvent mean?
The liquid in which a solute dissolves.
Eg - Water in sweater
What does solute mean?
The substance which dissolves in a liquid to form a solution.
Eg - the salt in seawater
What does solution mean?
The mixture formed when a solute is dissolved in a solvent.
Eg - Seawater
What does saturated solution mean?
A solution with the maximum concentration of solute dissolved in the solvent.
Eg - Sweater in dead sea
What does soluble mean?
describes a substance that will dissolve
Eg - salt
What does insoluble mean?
Describes a substance that won’t dissolve
Eg - sand in insoluble water
What does filtrate mean?
the liquid or solution that has passed through a filter
Eg - fresh coffee in a cup
What does residue mean?
A substance that remains after evaporation, distillation, filtration, or any other similar processes.
Eg - coffee grounds in filter paper
What do titration help determine in a solution?
method of analysing the concentration of solutions
What are indicators used for?
to show the endpoint of a titration
What is paper chromatography used for?
to separate substances that qhve different solubilities
What do locating agents help with?
to react with the same and produce a colored product to make a colorless substance made up of amino acids visible
What are the retention factor values used for?
- to identify the components of mixtures
What is the retention formula
Retention factor = distance travelled by substance / distance travelled by solvent
What is filtration used for?
- method of separation
- difference in solubility
What is the process of filtration?
- Filter paper is placed in a filter funnel above another beaker
- Mixture is poured into filter funnel
- Filter paper only allows small particles through
- Solid particles are too large and remain as residue.
What is crystallization used for?
to seperate a dissolved solid from a solution
How can you test if a solution is saturated?
Dipping a clean, dry, cold glass rod
What is the process of crystallization?
- Heat the solution, allow solvent to evaporate leaving a saturated solution
- Saturated solution is allowed to cool, solids come out of the solution as solubility decreases, so crystals grow
- Crystals are collected by filtering solutions
- Wash with distilled water and dry
What is simple distillation used for?
Sperate a liquid and a soluble solid from a solution.
Eg - fermentation (alcohol, water)
What is the process of simple distillation?
- Solution is heated, pure water evaporates producing water vapour, rising through the neck of round bottomed flask.
- Vapour passes thru condenser, condenses and turns into pure water.
- Solute will be left behind
What is fractional distillation used for?
separate two or more liquids miscible with one another.
Eg - petroleum
What is the process of fractional distillation?
- Solution is heated to a lowing b.p. of a substance.
- Rise and evaporate, water condenses which collects in the beaker.
- Substance is evaporated and collected
How do we assess the purity of a substance?
