RPA preparation of standard solution & titration Flashcards
What is a standard solution?
A standard solution is a solution of known concentration
How do you make a standard solution
Measure, using a balance, the mass of solid required
Transfer this to a volumetric flask and rinse the remaining weighing bottle content (with distilled water) into the flask so no solid is lost
Add a volume of distilled water to dissolve the solid. Swirl to mix
Then add more distilled water up to the line on the neck of the volumetric flask. Invert multiple times to mix
What is the standard solution for the practical. How is it made?
Diluted sulfamic acid
Dissolve 2.5g solid sulfamic acid in 100cm3 of distilled water
Transfer to 250cm3 volumetric flask and fill up to line with distilled water
What is the weighing by difference technique
Way of weighing materials accurately
Mass of substance = mass of weighing dish and substance - mass of dish after substance has been transferred
What equipment is used to carry out this titration?
A pipette and pipette filler are used to accurately measure out the volume of NaOH before transferring it to a conical flask
A burette is used to add small volumes of sulfamic acid solution to the NaOH until the reaction has reached completion
How do you carry out a titration
Once the pipette has been used to place NaOH into the conical flask, fill the burette with the acid solution
Add a few drops of methyl orange to the conical flask
Open the burette tap and allow the sulfamic acid to flow into the conical flask, swirling it to mix the contents
Close the burette tap once the expected colour change occurs. Use a white tile so the colour change is easy to identity
Record burette volume
Repeat until you get concordant results, then calculate a mean titre
Why are acid-base indicators used?
To detect when a reaction reaches completion, usually by the presence of a colour change
What are concordant results
Titres within 0.1 cm3 of each other
How would you analyse the results this titration
Calculate the concentration of the sulfamic acid solution
Calculate the mean tire using concordant results
Calculate the concentration of the burette solution
Hazards, risks in the lab
Bunsen burner –> burns –> keep away from flammable chemicals and away from the edge of the desk
Chemicals –> irritant, corrosive, to skin, lungs, eyes, toxic, flammable –> handling with care and while wearing gloves, wear eye protection, keep away from the edge of the desk and from an open flame. Don’t ingest
Glassware –> may break and cut you –> handle with care, keep away from edge of the desk
