Ch 21 - (Experimental Design and Separation Techniques)

Question 1

How can time be measured?

Answer 1

Stopwatch or stop clock to one or two decimal places

Question 2

What are the units of time?

Answer 2

Seconds or minutes

Question 3

How is temperature measured?

Answer 3

• Thermometer or digital probe
• laboratory thermometers have a precision of half or 1 degree

Question 4

What are the units of temperature?

Answer 4

degree Celsius (°C)

Question 5

How is mass measured?

Answer 5

Digital balance (2 decimal places)

Question 6

What is the standard unit of mass?

Answer 6

kg or g

Question 7

What is used to measure volume of liquids?

Answer 7

• Volumetric pipette (fixed volume; 10 - 25cm^3)
• Measuring or graduated cylinder (approx volume)
• Burette ( variable of volume; 0 - 50 cm^3)

Question 8

What are advantages of temperature probe versus thermometer?

Answer 8

• more precise readings
• easily take multiple readings
• use automatic sampling over longer periods of time

Question 9

What are disadvantages of temperature probe versus thermometer?

Answer 9

• probe can be corroded by some reagents
• probes more expensive to replace

Question 10

What is the advantage of volumetric pipette versus a measuring cylinder?

Answer 10

Pipette measures very acutely

Question 11

What is the disadvantage of volumetric pipette versus a measuring cylinder?

Answer 11

harder to sue and only measures one fixed volume

Question 12

What is the advantage of gas syringe versus inverted cylinder for collecting gases?

Answer 12

gas syringe are easy to set up and keep the gas dry

Question 13

What is the disadvantage of gas syringe versus inverted cylinder for collecting gases?

Answer 13

• piston can stick
• limited volume can be connected
• delicate and expensive

Question 14

What is the advantage of microscale versus normal scale quantities?

Answer 14

• less wasteful of regents
• saves energy
• safer

Question 15

What is the disadvantage of microscale versus normal scale quantities?

Answer 15

• hard to see what’s happening
• loses a lot of materials in separating and purifying products

Question 16

What does solvent mean?

Answer 16

The liquid in which a solute dissolves.

Eg - Water in sweater

Question 17

What does solute mean?

Answer 17

The substance which dissolves in a liquid to form a solution.

Eg - the salt in seawater

Question 18

What does solution mean?

Answer 18

The mixture formed when a solute is dissolved in a solvent.

Eg - Seawater

Question 19

What does saturated solution mean?

Answer 19

A solution with the maximum concentration of solute dissolved in the solvent.

Eg - Sweater in dead sea

Question 20

What does soluble mean?

Answer 20

describes a substance that will dissolve

Eg - salt

Question 21

What does insoluble mean?

Answer 21

Describes a substance that won’t dissolve

Eg - sand in insoluble water

Question 22

What does filtrate mean?

Answer 22

the liquid or solution that has passed through a filter
Eg - fresh coffee in a cup

Question 23

What does residue mean?

Answer 23

A substance that remains after evaporation, distillation, filtration, or any other similar processes.

Eg - coffee grounds in filter paper

Question 24

What do titration help determine in a solution?

Answer 24

method of analysing the concentration of solutions

Question 25

What are indicators used for?

Answer 25

to show the endpoint of a titration

Question 26

What is paper chromatography used for?

Answer 26

to separate substances that qhve different solubilities

Question 27

What do locating agents help with?

Answer 27

to react with the same and produce a colored product to make a colorless substance made up of amino acids visible

Question 28

What are the retention factor values used for?

Answer 28

• to identify the components of mixtures

Question 29

What is the retention formula

Answer 29

Retention factor = distance travelled by substance / distance travelled by solvent

Question 30

What is filtration used for?

Answer 30

• method of separation
• difference in solubility

Question 31

What is the process of filtration?

Answer 31

1. Filter paper is placed in a filter funnel above another beaker
2. Mixture is poured into filter funnel
3. Filter paper only allows small particles through
4. Solid particles are too large and remain as residue.

Question 32

What is crystallization used for?

Answer 32

to seperate a dissolved solid from a solution

Question 33

How can you test if a solution is saturated?

Answer 33

Dipping a clean, dry, cold glass rod

Question 34

What is the process of crystallization?

Answer 34

1. Heat the solution, allow solvent to evaporate leaving a saturated solution
2. Saturated solution is allowed to cool, solids come out of the solution as solubility decreases, so crystals grow
3. Crystals are collected by filtering solutions
4. Wash with distilled water and dry

Question 35

What is simple distillation used for?

Answer 35

Sperate a liquid and a soluble solid from a solution.

Eg - fermentation (alcohol, water)

Question 36

What is the process of simple distillation?

Answer 36

1. Solution is heated, pure water evaporates producing water vapour, rising through the neck of round bottomed flask.
2. Vapour passes thru condenser, condenses and turns into pure water.
3. Solute will be left behind

Question 37

What is fractional distillation used for?

Answer 37

separate two or more liquids miscible with one another.

Eg - petroleum

Question 38

What is the process of fractional distillation?

Answer 38

1. Solution is heated to a lowing b.p. of a substance.
2. Rise and evaporate, water condenses which collects in the beaker.
3. Substance is evaporated and collected

Question 39

How do we assess the purity of a substance?