Elements, Compounds & Mixtures
What is an element?
substance contains only one type of atom
What is the name of solution called collected from filtration method?
Hint: collected in conical flask
Filtrate
What is the difference in set-up of simple vs. fractional distillation?
Fractional distillation has a fractioning column.
Hint: used to condense back component with higher BP
What is the mobile phase?
Solvent
Which technique would you use to separate out salt from water?
Filtration
What is a compound?
Formed when two or more elements chemically combine in fixed proportions
What physical states is "filtration" used in separating?
Liquid & Solid
True/False - Should fractional distillation used for an immiscible mixture of 2 liquids?
False
How to calculate Rf value?
Rf = distance travelled by spot from start line divided by distance solvent travelled from start to solvent front
OWTTE
Which method would you use to separate out components of a mixture based on differing solubilities?
Paper chromatography
What is a heterogeneous mixture?
Mixture that is not evenly distributed
Which "component" is separated out when using crystallization?
Recall: solute + solvent = solution
Solute
BP within 25 degrees C of each other
What to do if Dye Y will not move from pencil line at all? Why is it not moving?
(i) Change solvent used
(ii) Not soluble at all in solvent
Which technique would you use to separate out soluble salt from water?
Use crystallization
(1) How can mixtures be separated?
***Hint: by what means...
(2) What does this mean?
(1) By physical means
(2) Changing Temperature/Dissolving [aka solubility]
(1) When to stop heating for crystallization?
(2) List 2 methods for when stop heating for crystallization.
1. Saturated solution
2. Crystals on side of evaporating basin/crystals on dipped glass rod
What is the function of condenser?
To condense the vaporized "sample" for collection in conical/round-bottom flask.
If dye X is very soluble in the solvent, which phase will it travel with & where will it be in relation to pencil line/solvent front?
Travels with (i) solvent, (ii) close to solvent front
Which technique would you use to separate out water from soluble CuSO4?
*Hint: collect solvent
Simple distillation
How could you test to see if sample is impure?
Use melting point.
A pure substance has a fixed melting point,
whereas a mixture will melt over a range of temperatures
State 1 of the above answersWhat steps to do filtration/crystallization after adding copper (II) oxide to acid while gentle heating?
***Hint: H2SO4 + CuO -->
[4 points to get 500]
1. First do filtration method --> (filtrate will be CuSO4)
2. Put filtrate into evaporating basin, and heat gently.
3. Heat until saturated/glass rod has crystals, then turn off heat.
4. Leave by windowsill or... OWTTE
What is found in the fractioning column? What is its function?
(i) Beads
(ii) Function is for liquid with higher BP that is vaporizing to condense back into liquid and collect back into original conical flask.
Explain steps for set-up of chromatography.
***Hint: 5 points for 500
1. Draw a line in pencil bottom of paper
2. Put a spot of ink equal distance apart of pencil line.
3. Add some solvent to beaker.
4. Put paper in beaker, solvent below pencil line
5. Leave paper in solvent until it travels close to top of page.
1-propanol (BP = 97 degrees C, liquid @ RT) and 2-propanol (BP = 82 degrees C, liquid @ RT) need to be separated.
What is appropriate method of choice? Which liquid will remain in original conical flask?
(i) Use fractional distillation
(ii) 1-propanol [because higher BP]