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Flashcards in Experiments Deck (296)
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Prep of a solution

-rinse pipette, burette, w/ d.i water, and with solutions/chemicals

(if using powder/crystals )-weigh out solute on weighed clock glass, subtract mass of clock glass
-put into (clean) beaker, rinsing clock glass w/ d.i. beaker to ensure all solute goes into it (rinsings)
-stir, dissolve
-use funnel, pour into volumetric flask, rinsing again as you do so using d.i. water
(If using a solution)-fill pipette with pipette filler up to mark with the bottom of meniscus on the mark
-transfer into volumetric flask using a funnel, then rinse funnel to ensure all of the solution goes into it

-fill up close to the mark with d.i. water, add final amount using dropper until bottom of meniscus on mark. Read at eye level.
-stopper, invert several times to ensure solute uniform through solution


Iron tablet experiment - procedure for making up solution

-crush tablets with mortar and pestle
-washed into beaker
-stirred to dissolve
-transferred into flask using funnel
-rinsings added to flask
-add using dropper
-top up carefully until bottom of meniscus level with mark
-stopper, invert multiple times


iron tablet - why use dilute sulfuric acid in making up solution

to prevent air oxidation of Fe²⁺ in solution to Fe³⁺


iron tablet - why was more dilute sulfuric acid added before titration commenced?

to prevent formation of manganese(IV) (Mn⁺⁴) (brown precipitate) in solution


iron tablet - how was end-point detected?

colourles to pink


iron tablet - why nitric acid could not be used to provide acidic conditions for this reaction

nitric acid could not be used as it is a strong oxidising agent


measuring the heat of neutralisation (of ethanoic acid by sodium hydroxide) in the school laboratory

-suitable container (polystyrene cup / calorimeter / glass vessel such as beaker) of known head capacity
-known vols & concs of acid and base
-measure initial temp, mix and note new (highest) temp
-calculate heat produced using mcdeltatheta
-calc for 1 mole H+ / calc heat of neutralisation


why ethanoic acid and sulfuric acid would have diff heats of neutralisation

sulfuric acid: strong acid - dissociated, present as ions, energy not needed to dissociate)

ethanoic acid: weak acid (undissociated, slightly dissociated, present as molecules, energy needed to dissociate)


water of crystallisation experiment - primary standard reagent which could have been used to standardise the HCL solution

anhydrous sodium carbonate


water of crystallisation experiment - suitable indicator, colour change,

methyl orange

yellow to red


water of crystallisation experiment - why not more than 1-2 drops of indicator should be used

methyl orange is a weak acid


describe the correct procedure for rinsing the burette before filling it with the solution to deliver + describe filling it

rinse with deionised water
rinse with solution

-use funnel, pour in at top, take meniscus into account
-remove funnel
-ensure area below tap is filled


why is it important to fill the part below the tap of the burette?

air will be displaced by solution


describe procedure for weighing + making up solution from hydrated sodium carbonate crystals (for powders/crystals)

-weigh on clock glass using electronic balance
-transfer solution to beaker + rinse clock glass with d.i water using wash bottle to ensure all is transferred
-dissolve in d.i water
-transfer to volumetric flask using funnel + rinse with d.i water to ensure all is transferred
-add d.i water to up to near mark on flask
-add final amount using dropper, taking meniscus into account
-stopper, invert several times


describe procedure for washing the pipette and using it to measure the solution

-rinse with d.i water, followed by solution

-fill up to mark with pipette filler taking meniscus into account
-transfer to flask with tip against side of flask to avoid splashing


three precautions with burette that should be taken in order to ensure an accurate measurement

-vertical/read at eye level
-add dropwise using dropper near end-point
-rough titration first


sodium carbonate crystals, is not a primary standard but anhydrous sodium carbonate (Na₂CO₃) may be used as a primary standard. Why is this the case?

-Na₂CO₃ is pure, stable, anhydrous (not hydrated), no water loss
-solution of exact concentration can be made, no need to standardise by titration, any opposite point for sodium carbonate crystals


proceedure to measure out water from a beaker to a conical flask

-rinse pipette with d.i water and then the water sample
-use 25cm² pipette twice
-read mark at eye level, bottom of meniscus on mark
-touch tip against inside wall of conical flask, empty it out, do not blow out last drop from pipette


describe how the melting point of the crude product/recystallised product of benzoic acid could have been measured

-know diagram

-sample on heating block
-thermometer in melting block
-block heated
-note temp range over which sample melts


melting point benzoic acid experiment - two ways how you could conclude from melting points that the recrystallised product was purer than crude product

-higher melting point
-melting point closer closer to correct (in tables) value
-sharper (narrower range)


one important use of benzoic acid or its salts

-food preservative
-disinfectant (antiseptic, fungicide)


describe the flame test

-dip platinum wire in HCl to clean, clean if it does not change flame colour
-dip in HCl
-dip in sample of salt, sticks to wire
-place salt in/over Bunsen flame
-note colour of flame observed
-if question specifies a salt, write the colour the flame should turn into


flame test - the metals and their colours

Barium nitrate: yellow-green

Copper sulfate: blue-green

Lithium carbonate: deep red

Potassium sulfate: lilac

Sodium sulfate: yellow

Strontium nitrate: red


flame test - why do metals give off a characteristic colour in a flame?

energy differences between energy levels in metal atoms vary from metal to metal. Using energy from flame, electrons move to higher energy levels then return to lower e levels, emitting light whos energies are equal to energy diff between higher e levels and lower e levels.


flame test - what procedure is used to avoid cross contamination?

Platinum wire: cleaned with concentrated HCL after each test

Wooden splint: diff splint used for each test


redox reactions of halogens - What is observed when chlorine gas is bubbled into an aqueous solution of sodium bromide? Explain your answer in terms of oxidation and reduction.

-solution turns red-brown

-bromide ions oxidised to bromide
Br⁻ --> Br₂

-chlorine reduced to chloride ions
Cl₂ --> Cl⁻


How do halogens react? + order of oxidising power

As oxidising agents, as they often react by taking an electron from another element.

F > Cl > Br > I > At


Why some halogens cant be used for the redox reaction

-Fluorine extremely poisonous
-Astatine unstable + radioactive


Ethanoic acid in vinegar - measuring sample of vinegar and diluting it with d.i water

-use pipette previously rinsed with deionised water and then rinsed with the vinegar solution it will contain
- pipette: read at eye-level, bottom of meniscus on mark, don't shake out/blow out last drop

-transfer to volumetric flask previously rinsed with deionised water, fill with d.i water until bottom of meniscus on mark (dropper at end), stopper + invert number of times


Ethanoic acid in vinegar - indicator