Experimental techniques

Question 1

True or false: only a strong acid will 100% deionize

Answer 1

true

Question 2

Idiometric titrations

Answer 2

used to determine the concentration of an oxidising agent in solution. A starch solution is used as an indicator since it can absorb the I2 that is released

Question 3

Why should KIO3 be added in excess

Answer 3

to keep iodine dissolved

Question 4

What does the AA solution contain?

Answer 4

HCl (5mL), KI (5mL), starch (2mL)

Question 5

What happens to the KI in the solution?

Answer 5

reacts with the potassium iodate, leaving I2

Question 6

What happens to the concentration of Vitamin C as temperature/pH/light/metals/oxygen increases?

Answer 6

decreases (Degradation)

Question 7

Why do we work in fumehoods?

Answer 7

protect us from inhaling toxic gasses

Question 8

How do you know if the fumehood is pulling air from inside?

Answer 8

the paper will start blowing inwards

Question 9

Where must the window sash be?

Answer 9

Under the black arrow

Question 10

can you put your head under the glass?

Answer 10

NO

Question 11

Where can the work be done?

Answer 11

behind the blue line

Question 12

What do you have to do to the solution in a flask before taking it out of the fumehood?

Answer 12

Stopper it

Question 13

What temperature does the solution need to be at before pouring into a seperatory funnel

Answer 13

room temperature (20)

Question 14

How many times should you vent and rock the funnel?

Answer 14

at least 5 times

Question 15

Where do you hold the top when you vent?

Answer 15

Away from you or other people

Question 16

What do you leave out from the beaker you pour your seperated solution to?

Answer 16

the bubble layer

Question 17

What is sublimation?

Answer 17

technique used to purify a solid chemical substance

Question 18

Steps for sublimation

Answer 18

• the substance is placed into a vacuum filter flask that has been fitted with a cold finger, and then the flask is placed on an electric hotplate
• the water pump is turned on to lower the pressure within the vacuum filter flask, and simultaneously the heat is turned on

Question 19

Sublimate

Answer 19

The condensed substance

Question 20

Where does the sublimate form?

Answer 20

The hot chemical vapours rise until they hit the cold finger, where the vapours condense onto the cold finger.

Question 21

What happens to the impurities

Answer 21

impurities will either not sublime and remain at the bottom of the filter flask, or will not condense and be sucked out of the flask by the water pump.

Question 22

Melting point analysis

Answer 22

used for the identification of a compound and its purity

Question 23

If a substance contains impurities

Answer 23

will melt at a lower temperature than the pure compound, and melts over a wide range of temperatures

Question 24

In general

Answer 24

the smaller the range of melting
temperatures, the higher the purity of the sample

Question 25

Steps for melting point

Answer 25

• load a sample into a melting point
  capillary tube and then slowly heat up the tube in a melting point apparatus.
• record the temperature at which the sample begins to melt AND the temperature at which all of the sample has melted.

Question 26

What are rotary evaporators used for

Answer 26

to remove solvents from a solution through evaporation

Question 27

Steps for rotary evaporation

Answer 27

An RBF is clamped to the rotary. The vacuum is turned on, and the RBF is lowered into the hot water bath. The rotary is then turned on.

Question 28

How does the rotary evaporation work

Answer 28

The solvent in the RBF is heated and evaporates out of the top of the flask which goes in the condensor, where the solvent cools due to the cold water that is in the condensor, which evaporates. The solid is then left in the RBF

Question 29

why do we use calorimetry?

Answer 29

so we can identify solutes in a coloured solution and very accurately determine their concentrations

Question 30

How Does Colourimetry Work?

Answer 30

Colourimetry is a form of spectroscopy, which measures how atoms or molecules respond when exposed to electromagnetic radiation of a certain wavelength within the visible light spectrum.

Question 31

Beers law

Answer 31

A = ε l c

Question 32

analytical wavelength

Answer 32

wavelength of max absorbance

Question 33

SEROLOGICAL PIPET

Answer 33

Pipets with graduations along the length of the tube, kinda similar to a syringe

Question 34

how do you measure on a serological pipette?

Answer 34

You measure backwards, for example if you want 3 ml, you measure to the 7 ml mark

Question 35

How to calibrate analytical wavelength

Answer 35

Select all wavelengths in advanced settings and then run a blank. Then click on absorbance and run a 10 mL sample of dye. Record the highest wavelength

Question 36

How to collect data using spectrophotometer

Answer 36

Click the wavelength and all the boxes in the same column. Run a blank the set the time interval to 5 seconds. Turn the stirring on and reversing off.

Question 37

Measuring pH

Answer 37

measured with a pH probe, which is a sensor containing a combination of two electrodes. first electrode has a fixed voltage and the other (glass) electrode uses it as an electrode. the pH should match with the voltage on the glass second electrode

Question 38

When not in use where should the pH probe be kept

Answer 38

stored in the pH 7 buffer solution

Question 39

What do we measure in a pH titration?

Answer 39

the change in pH of the solution being titrated
- plot the volume of the titrant added on the x-axis and the pH on the y-axis

Question 40

Drop dispenser

Answer 40

A liquid is put in it and the flow rate is set so that you can determine the size of the drop that comes out of the tip. This way drops can be converted to mL.

Question 40

Drop counter

Answer 40

Each drop that comes out passes by a sensor on the drop counter and is counted and plotted on the pH curve by adding a formula

Question 40

Where does the pH probe go when the titration happens?

Answer 40

on the side of your solution, dont let it touch the magnetic stirrer

Question 41

Formula

Answer 41

Volume = counter * mass of drops / number of drops

Question 42

How many drops should you weigh and measure?

Answer 42

100

Question 43

How do you set up a microlab drop counter

Answer 43

Click on add sensors and set it to “counter”. Click “set counter options” and click “continually increasing count”. Finish and go down further. Make sure it is says “count every drop”. Then add another sensor and click pH, the add a new calibration point by changing the 0 to a 7 and wait until the red line is in between the green section. Then drag the sensors to the graph.

Question 44

How do you callibrate the drop dispensor

Answer 44

Fill the drop dispenser with water and make sure it flows. Weigh an empty beaker and record it. Let the water flow until 100 drops are counted then re-weigh the beaker. Enter the formula into the program.