Exercise Apparatus And Techniques, Exercises of Analytical Chemistry

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A volume of 50. 0 mL of solution X is to be added to another vessel. A student

decided to use a 50. 0 mL volumetric flask to measure out the volume of the

solution X. State whether the correct measuring glassware has been used.

i) State the function of a desiccator.

ii) Name two desiccants that can be placed inside the desiccators.

No ,^ It^ is^ designed to^ contain^ an^ accurate^ volume^.

i

) A^ desiccator is^ used to^ keep^ samples^ dry^ while (^) they are^ cooling^ and before (^) they are^ weighed^

and ,^ in^ some^ cases^ ,

to dry the^ wet^ sample^

. Ii (^) ) Any

two suitable^

desiccants i

• (^) calcium chloride
• silica (^) get
• (^) calcium sulphate

a) Propose one apparatus that can be used for drying heat-sensitive

sample.

b) Explain the difference between distilled water and deionized water.

c) Using an example distinguish between ‘TC’ and ‘TD’.

d) Discuss how to prepare a standard solution using a volumetric flask.

: Desiccator

; pipe t

• Distilled water
• Distilled water is^ prepared using distillation (^) process
• Contains no dissolved menirals (^) , chemicals (^) & (^) impurities
• (^) Removes more than^ 99.8% of most^ tap water^ impurities , (^) Including

Cryptosporidium

• (^) Deionized water
• (^) Deionized (^) water is prepared using^ 10h^

exchange process

• contains of organic Impurities
• (^) Does not (^) contain (^) ion such (^) as (^) ca"

. Na^

" , C

• ,^ Br - except 1-^ "

& OH^?

= Pipette

• (^) TC - to (^) contain the (^) specified volume

* It^ pipette is^ labeled as tc , the small

remaining

volume should (^) be shaken or (^) blown out to obtain the^ correct amount of^ material.

• (^) TD - to (^) deliver (^) the

specified volume^ at^ the^ calibration^ temperature.

* If pipette is labeled as TD , a certain small volume will remain in^ the tip.

this should^ not^ be^ shaken^ or^ blown^ out.

it A^ transfer pipette is

designed to^ deliver^ a^ single^ fixed^ volume

of solution^ such^ as 10mL , 20mL Or 25mL.

ii ) Actual Volume of the

pipet :^ 19-^ ✗ (^) 1.0030 mL = (^) 19.909 mL g ' technical (^) grade '

chemical reagets are of low^ purity therefore^ are

not suitable for

preparing standard^ solution^.^ Standard^ solution^ should

be (^) prepared (^) using primary standard^ chemical^ reagent

Deionized water^ is^ produced via ion exchange chromatography.

Tap water^ is^ passed through ion^ exchange resin^ which^ has

strong acid^ resin^ and^ strong base^ resin that^ replace or^ exchange

cations and anions (^) from water for Ht^ and (^) OH _

respectively. Exchanges

of the 10ns occur on

binding sites^ of the (^) resin (^). Soaking in^ warm^ detergent

cleaning using chromic^ acid^

or (^) dilute (^) nitric acid or aqua (^) regia

Ultrasonic

cleaning

Before using the analytical balance

,

it should be warmed up for^ at^ least

half an hour - Before

turning on^ ,^ be^ sure^

that the^ doors^ are^ closed

and the^ pan Is^ not^ touching^ the^ draft^ ring.^ Never^ hold^ objects to^ be weighed by^ hand / (^) finger. Use (^) tongs.^ Dust^ pan lightly before (^) and after weighing (^) object.^ Center^ load^ as^ well^ as^ possible^.^ Never^ weigh^

heated

objects. Allow (^) object to cool^ first^ - Always close - balance case^ door^ before^ taking the (^) weight of (^) Object. Air current^ causes balance to^ be^ unsteady. Never (^) place chemicals^ directly on^ the^ pan , but^ weigh^ them (^) in a^ Nessel ( (^) weighing bottle^ dish^ boat^ small beaker^ )

it • Bunsen

burner

• (^) hot (^) plate
  • (^) electronic (^) oven
• (^) microwave
• (^) furnace

ii 1 A warm

object sets^ up convection^ currents inside the balance (^) enclosure (^) , which (^) will (^) make an (^) object appear tighter than (^) it really is^.