S 13 71 787
Ali Hussain Wed PM, Group 3 Experiment 5: Analysis o an Al!a Selt"er Selt "er #a$let #a$let
Aim
The aim of this experiment is to ind out the active components of an Alka Seltzer tablet by calculating the percentage by mass of sodium hydrogen carbonate the tablets contain. Then using UV spectroscopy spectroscopy the !uantity of salicylate in a tablet "as to be found. Pro%edure
#n part one of the experiment six solutions "ere made of deionised "ater and ethanoic acid. The "eight of the deionised "ater and beaker "ere recorded. An Alka Seltzer tablet "as added to the beakers and "eighed as "ell once the effervescence had stopped. The six solutions "ere made as follo"s$ Volume of "ater %cm&'
Volume of ethanoic acid %cm&'
Solution (
&).*
*
Solution +
&*.*
).*
Solution &
+).*
(*.*
Solution ,
().*
+*.*
Solution )
).*
&*.*
Solution -
*
&).*
rom the results obtained a graph of calculated percentage by mass of /a012& versus volume of ethanoic acid. rom all the solutions made solutions +3- can ca n be disposed4 solution ( needs to be kept for part +. #n part + of the experiment (* cm & of + 5 sodium hydroxide hydroxide is added to the solution ( beaker. beaker. Anti3bumping granules are also added to this solution and boiled for (*
S1371787
Ali Hussain
Wed PM, Group 3 minutes. The solution is then cooled and transferred to a volumetric lask and made
up the mark "ith deionised "ater. (* cm& of this solution is transferred into another lask and )* cm& of iron %###' nitrate solution is also added to that lask and made up to the mark "ith deionised "ater. The absorbance at ),*nm of this solution "as measured and the concentration of salicylate present could be measured using the 6eer37ambert la". &esults
Table ($ 8eight
8eight of 8eight of
8eight
5ass of
9ercentage
of
tablet %g'
beaker
difference
/a012&
by mass
beaker
solution
%mass of
reacted
/a012&
and
and tablet 12+ %g''
%g'
%:'
solution
%g'
%g' Solution (
;).),)
+.;;)
;<.==*
*.,,
*.;,
+=.(+:
Solution +
;&.<++
+.;;)
;).<(&
*.;=,
(.<(
)=.+<:
Solution &
;&.),<
+.;;)
;).-;;
*.<,,
(.,+
,=.++:
Solution ,
;).++=
+.;;)
;<.+=<
*.;(<
(.)-
),.*<:
Solution )
<<.+&<
+.;;)
<=.&+<
*.<=)
(.)+
)+.-=:
Solution -
<=.)=+
+.;;)
;(.<,=
*.<+;
(.&=
,;.(;:
1alculated percentage by mass of /a012& versus volume of ethanoic acid
S1371787
Ali Hussain Wed PM, Group 3
x axis > volume of ethanoic acid %cm &' y axis > percentage by mass of /a012& 'al%ulations
1alculating the concentration of salicylate A?@cl 1?A@l 1?%*.=*;'%).,x(*B3)cm'%,<)+ dm& cm3(' 1? &.)5 (is%ussion
The results of part ( allo"ed table ( to be produced and completed. The "eight diiference %mass of 12+' "as calculated by adding the "eight of the beaker and solution "ith the "eight of the tablet and subtracting it from the "eight of beaker solution and tablet. The mass of /a012& reacted "as calculated by using the formula$ 5ass?5ass of carbon dioxidemolar mass of carbon dioxide C molar mass of /a012& The percentage by mass of /a012& "as calculated by the formula$ 9ercentage 5ass ? mass of /a012& reactedmass of tablet C(**:
S1371787
Ali Hussain
Wed PM, Group 3 The data collected in part ( %solution (' and part + "as used to calculate the
concentration of salicylate present &.)5. The 6eer37ambert la" "as used to carry out this calculation. A slight problem occurred "ith the results for the absorbance because in part + the inal solution "as not made correctly. The solution "as too concentrated4 therefore the UV spectrophotometer "as sho"ing an absorbance of (.*. So "e took the absorbance results from another group "ho found it to be *.=*;. )uestions
(. 012& > %a!' D 0D %a!'
0+2 %l' D 12+ %g'
→
+. 1itric acid > 1-0;2< &. #U9A1 name for acetic acid > ethanoic acid ,. The dissolving of 12+ in reaction solution "ill lead to too small a value of percent by mass of /a012& in Alka Seltzer tablets. The evaporation of "ater "ill lead to too large a value of percent by mass of /a012& in Alka Seltzer tablets. The evaporation of "ater may be corrected by subtracting the "eight loss of a blank solution from the "eight loss of the reaction. The !uantity of dissolved 12+ can be estimated by the information used in published articles$ (* m7 -5 01l solution absorbs about &.* E (*3, mol of 12+ %+'. This value should be added to the "eight loss obtained.
). 8hen /a012& is in excess the acid %0D ' in the reaction is the limiting reactant. 2n the other hand "hen the acid is in excess sodium bicarbonate becomes the limiting reactant. Since the amount of sodium bicarbonate in a tablet is ixed the amount of 12+ generated remains constant regardless of the !uantity of vinegar added. -. 5ass ? +;,mg <. The packaging says the mass of aspirin is &**mg and the slight difference could have been caused by the impurities found in the +;,mg sample.
'on%lusion
S1371787
Ali Hussain
Wed PM, Group 3 This experiment dealt "ith investigating the active components of Alka Seltzer
tablets and determining the percentage by mass of sodium hydroxide carbonate the tablets contained %Table ('. The !uantity of salicylate in each tablet "as also calculated &.)5. 6ecause of the error that occurred in part + results for the absorbance %*.=*;' had to be taken from another group.
