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Unit 2 A1 Learning aim A: Undertake titration and colorimetry to determine the concentration of solutions
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Quantitative Chemical AnalysisCalibration of measuring instruments
Brief report on the calibration of a balance
The calibration is helpful in showing whether a scientific instrument is working accurately & how it
can show how the calibrations are engineered to give the correct values.
For instance, the balance needs to be calibrated because a factor like magnetic field plays a role in
this, as such if someone was to move it will affect the accuracy of it and it decreases the probability of
weighing mistake that will ultimately cost extra money, it allows essentially that it makes a well
decision that avoids product recalling. The reliable measurements can be compatible which will help
in with the final product (achieving accurate weighing results if this wasn’t important then many
technicians would have to guess). The balance should be placed in an area that will ensure that it
gives a steady reading when weighing.
Things like external factors like mechanical shocks, hazardous environments, no leaning as well as
placing equipment near to it, the area should be quiet as its sensitive to weights (calibration balances
are very expensive so should be taken care well). The following things that need to be done is that
before starting the calibration balance the machine asks for the weight it wants, then on the machine it
shows that it done & levelled. Then try to make sure that its cleaned and by handling the calibration
masses try to use gloves to prevent damaging the weights.
The weights used were of metal origins are the sizes of weights used were 200g-300g which was read
by 2 decimal places, this was used to show the accuracy of the calibration. Moreover, by ensuring that
on the balance shown how its started and what to do during calibration. These factors can be affected
by many things occurring the following may be like making sure that its levelled, the locking
mechanism is off, and the pan is clean (sliver-kind plate), these will help accomplish detection of
equipment ages over time and process and profit improvement.
Brief report on the calibration of a pipette
The procedure of this goes as follows weigh a dry empty beaker and record the mass of it to 2 decimal
places this helps to ensure that its accurate, then to transfer 25cm3 of distilled water to the beaker
using the graduate pipette and pipette filler, then to reweigh the beaker with the water and like above
to measure it to 2 decimal places also it fits the manufacture’s tolerance. Then the final two steps are
that to empty the beaker and dry it with a paper towel. Then to ensure that it’s a fair test so that it’s an
accurate reading as to repeat steps 1 to 4 as to two more times.
The records of the mass of the beaker and water & as empty & the water as pipetted & to give an
average mass of water pipetted, the water temperature, and the density of water. Finally, to calculate
the average volume of water delivered by the pipette using a rearrangement of the formula to ensure
to calculate the density the equation is: average volume of water = average mass of water/density of
water.
Here is a results table showing the calibration of pipette experiment done in laboratory.
Mass of beaker + 94.14g 95.08g 93.96g
water/g
Mass of beaker 68.34g 68.36g 68.38g
empty/g
Mass of water 25.8g 26.72g 25.58g
pipetted/g
Mean mass of water 59.97g 60.9g 26.03g
pipetted/g
Water temperature/0C 22.20C 23.20C 22.20C
3
Density of water/g cm 2.3988 2.436 0.998 g cm3
Here is a results table showing the calibration of pipette experiment done in laboratory & there is a
small difference of the density of the water as in the first one which is lower by a few decimal values.
,This suggests that the second column has a higher density that was used in the calibration of the
pipette. The balance practically the electrical balances, the balances I estimated were to two decimal
places.
Titrations using indicators
Introduction of overview of titrations
The aim for first session is to make a standard solution of sodium carbonate which is the primary
standard and for the second session was to use the standard solution of sodium carbonate to find the
concentration of a hydrochloric acid solution so that it can be used as a secondary standard and for the
second session was to use the hydrochloric acid to find the concentration of a sodium hydroxide
solution.
Health & safety considerations involved with making a standard solution
The risk assessment for making a standard solution consists of it being an alkaline as sodium
carbonate isn’t harmful when it meets the skin, however COVID-19 Safety rules like social
distancing, the tutor wearing a visor, and equipment are all disturbed out to avoid touching a lot. The
reasons behind following risk assessment for COVID-19 to stop the virus from spreading and the
consequence of not following the rule it can be harmful to people’s health and will require for the
technicians to clean a lot of areas of which students had touched as the virus can stay on surfaces for
at least forty days, so by ensuring the following the risk assessment and limiting the consequences of
people getting infected, as such linking to the tutor handing out papers safely but not coming in too
much contact because by social distancing will limit the transmission because the consequences of not
following instructions can lead people who cough and sneeze can lead to transmission amongst the
staff, the virus can be spread by fluids. Only entering a laboratory when instructed by the tutor
because this can minimise people from overcrowding and cause damage to equipment and areas so
that if there are chemicals that have been used that can be inhaled its quite dangerous, so by avoiding
this will protect the people and the equipment and will limit a lot of contact. Also, by never
consuming food or drink in the laboratory the consequence of not following this can lead to food
ingestions and chemically contaminated drink that are sources of chemical exposure, so by following
this rule will prevent from getting ill. Wearing personal protection equipment: lab coat and eye wear,
by following this rule will stop sodium carbonate solution from going in the eye because it can cause
permanent corneal injury and the possibility of burns. So that’s the reason is wearing eye wear to
avoid this and for the apron this is to avoid stains and clothes from getting dirty (EH&S Blog, 2015).
Always standing when doing experiments so that people can go by, so people are able to walk to get
the equipment needed, by staying just sitting can be hard as people need , if anything falls on the skin
you need to make sure to wash with water, as it can cause burns and report to the tutor if very serious,
reporting any small spills to the tutor will because it will prevent people from falling and hurting
themselves as the consequences are that people can suffer from injuring themselves. Never putting
waste solids in the sink and by putting all the waste liquids and solids as it should be things should be
put away in dirty glassware and equipment in the designated areas and wiping down any spillages and
will prevent glassware from breaking.
Discuss the calibration of the balance and why?
The calibration of the balance was clean at first and was calibrated to numbers between 1.2g and 1.4g
in mass, the reason why was to ensure the balance was accurate for a range of masses, to calibrate the
balance a mass was placed on the balance and a calibration buttons was used to adjust the balance to
make sure that its 0:00 and the measurements had to be recorded to 2 decimal places as it made it
more accurate this was to make sure that it’s a fair test and to make sure that when calculating the
molarity seems to be accurate and in range with the whole class and I made a note of the measurement
on my results sheet on the table.
Explain steps you took?
Just a reminder that 1ml is the same 1 cm3 Once I did the calibration I poured the sodium carbonate
into a 250cm3 and filled it with 100cm3 of distilled water, I used the rough markings on the beaker
because the volume marks on a beaker are only approximate values and therefore only can provide the
, whole numbers as it would be difficult to gauge the exact volume of a liquid sample falling between
60 and 80. And then I washed off any sodium carbonate that stayed on the watch glass that stayed on
the watch glass into the beaker with distilled water and then I used a clean glass rod to stir the sodium
carbonate as it helps to dissolve in the water and then I washed off any solution that was on the glass
rod with distilled water and also to break any lumps. Then I poured the sodium carbonate solution into
a 250cm3 volumetric flask using a small glass funnel and washed the funnel with distilled water. And
then filled the volumetric flask with distilled water until the bottom of the solution’s meniscus tests on
the graduation line. And then I labelled it with my name, the date, what the solution is, and the mass
of solution in the volumetric flask.
Explain where you considered accuracy and why you needed to do this?
The standard solution can be helpful in finding the accuracy of a known concentration as it must be
prepared directly from a solute if that solute is a primary standard. And the sodium carbonate must
have a high purity as this can help to ensure the mass of the sample weighed out in a composed
entirely to the substance itself and nothing else, as if there were impurities of the true mass, then the
substance present would be less than the measured mass and this would lead to the solution having a
concentration less than the calculated value. And as it was in stable air and in solution and if this
wasn’t for the case then some of the substance used up in reacting with chemicals in the air or with
solvent, as a result which can lead to when the true concentration of the resulting solution would be
less than its calculated value and it must be readily soluble in a solvent and its solubility should be
high so that the solutions of a relatively high concentration should be prepared and it should have a
reasonably large relative formula mass this is to minimise the uncertainty in the mass of the substance
weighed out for example anhydrous sodium carbonate Na2CO3 is considered to be a base. I washed
the sodium carbonate with deionised water this is to remove excess sodium carbonate in order to give
it an accurate result that is in range within 1.2g-1.4g and also tap water wasn’t used because it
contains impurities that could interfere with the solution and the glass rod was used to break down the
lumps so that everything is evenly spread out and then by pouring the sodium carbonate using a big
glass/plastic funnel (I used the glass one as it showed if there was any residue) and then the
volumetric flask was used the advantage of this is that as it has a long neck it help in being used to
measure accurate volumes of liquids and to mix without causing a spillage and also volumetric flask
are accurate then cylinders or pipettes as its made out of glass its good to write things on it and its
cheaper for it show any step that you did wrong like any lumps of sodium carbonate and residue of
deionised water. The good thing about the meniscus it shows you exactly when to stop pouring,
however the first time I went over the meniscus so then I decided to do it again as per required by the
practical and I had to do it again by using a pipette, as the solution got closer to the meniscus, so that
its on the graduation mark I used a pipette to ensure that its accurately done and I was ensuring that
my eyes are at level with the graduation. Then you had to invert the flask, I did it 20 times as to mix
the solutions and if done once or twice the contents are not mixed properly and the solution will not
be in uniform. I managed to do it as accurately as possible the techniques I used where very well done
as I used a lot of online resources like YouTube to understand how to do good practical’s by
following the health and safety rules and knowing where the equipment were and things I had to
watch out for like measuring sodium carbonate between 1.2g-1.4g and making sure that the solution
didn’t go above the meniscus, but what I should have improved was that I should have been a bit
quicker in my experiment, making sure that I had a steady hand because I was on the edge of making
a mistake for my second attempt and a lot of deionised water was used so there was a lot of water
usage so I had to quickly clean up also by knowing what the units are can help to identify what to look
out for as 1ml = 1cm3 this is essential as so it doesn’t confuse you.
Here is a table showing the amount of the standard solution that was weighed by using a watch glass
as shown its between 1.2g-1.4g.
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