Studenti tal-10ar Sena tal-Kimika fl-Azzjoni
F’dawn ix-xeni, l-istudenti tal-10ar Sena tal-Kimika wettqu esperiment ta’ titrazzjoni. B’titrazzjoni nifhmu teknika analitika fil-kimika li matulha, soluzzjoni ta’ konċentrazzjoni magħrufa (is-soluzzjoni standard) tintuża sabiex tiddetermina l-konċentrazzjoni tas-soluzzjoni mhux magħrufa.
Wara li jittieħdu l-passi kollha sabiex l-apparat kollu magħmul mill-ħġieġ jinħasel kif jixraq, l-istudenti kellhom bżonn pipetta volumetriċi u tagħmir li jimla l-pipetta (pipette filler) biex ikunu jistgħu iħejju flixkun koniku b’volum preċiż (25ċm3) ta’ soluzzjoni standard (0.1M ta’ soluzzjoni ta’ sodju karbonat). Żdiedu xi taqtiriet ta’ indikatur imlewwen (metiloranġju) fil-flixkun sabiex, eventwalment, jiskopru l-endpoint tat-titrazzjoni (il-punt tan-newtralizzazzjoni). Wara poġġew buretta (mimlija b’soluzzjoni ta’ aċidu idrokloriku ta’ konċentrazzjoni mhux magħrufa) fuq il-flixkun konali u tniżżel il-valur tat-titlu inizzjali. Żdied l-aċdu idrokloriku qatra qatra fil-flixkun sakemm ir-reazzjoni ta’ newtralizzazzjoni kienet kompluta, li wassal għal tibdil fil-kulur. L-istudenti mbagħad niżżlu il-volum finali tal-buretta, biex b’hekk instab il-volum totali tal-aċdu idrokloriku (il-valur tat-titlu). Din it-titrazzjoni reġgħet saret tliet darbiet sabiex jinkisbu mill-inqas żewġ valuri tat-titlu konkordanti (b’differenza ta’ +/- 0.1ċm3) u ttieħed il-valur medju.
Matul dan l-esperiment, l-istudenti mxew ukoll mal-prattiċi tas-sigurtà fil-laboratorju u kisbu ħiliet esperimentali xierqa, tħarrġu fil-kitba xjentifika u fil-mod kif għandhom jiġu rrekordjati r-riżultati, kif ukoll fil-ħila dwar kif għandhom jaħdmu f’tim.
Prosit lill-istudenti kollha tal-10 Sena tal-Kimika!
In these scenes, the Year 10 chemistry students performed a titration experiment. A titration is a analytical technique in chemistry where a solution of known concentration (the standard solution) is used to determine the concentration of an unknown solution.
After taking into consideration the steps about washing the different glassware apparatus carefully, the students required a volumetric pipette and a pipette filler to prepare a conical flask with a precise volume (25cm3) of the standard solution (0.1M sodium carbonate solution). A few drops of colour indicator (methyl orange) were added to the flask to eventually detect the endpoint of the titration (point of neutralisation). Then they placed a burette (filled with hydrochloric acid solution of unknown concentration) above the conical flask and the initial titre value was recorded. Hydrochloric acid was added dropwise into the flask until the neutralisation reaction was complete, causing a colour change. The students then recorded the final volume of the burette, so the total volume of hydrochloric acid (titre value) was found. This titration was repeated three times to obtain at least two concordant titre values (differing +/- 0.1cm3) and an average value was taken.
During this experiment, students also maintained safe laboratory practices and achieved proper experimental skills, scientific writing, and record-keeping, as well as the skill of working in a team. Well done to all Year 10 Chemistry students!
Mr. J Borg
Chemistry Teacher