RP 1 - Making up a standard solution and carrying out an acid-base titration

Question 1

What’s a standard solution?

Answer 1

A solution of known concentration

Question 2

How do you make a standard solution?

Answer 2

1. Measure, using a balance, the mass of solid required
2. Transfer this to a volumetric flask and rinse the remaining weigh in bottle content (with distilled water) into the flask so no solid is lost
3. Add a volume of distilled water to dissolve the solid. Swirl to mix
4. Add more distilled water up to the line on the volumetric flask. Invert multiple times to mix

Question 3

What’s the weighing by difference technique?

Answer 3

• A method to weigh materials accurately
• Mass of substance = Mass of weighing dish and substance minus Mass of dish after substance has been transferred

Question 4

Explain which equipment are used uniquely (in spec) to carry out a titration?

Answer 4

• A pipette and pipette filler are used to accurately measure out the volume of a reactant before transferring it to a conical flask
• A burette is used to add small volumes of one reactant to other reactant (until the reaction has reach completion)

Question 5

How do you carry out a titration?

Answer 5

1. Once the pipette has been used to place one reactant into the conical flask, fill the burette with the other reactant. Record initial volume
2. Add a few drops of indicator to the conical flask
3. Open the burette tap and allow the reactant to flow into the conical flask, swirling it to max the contents
4. Close the burette tap once the expected colour change occurs. Use a white tile so the colour change is easy to identify
5. Record the final burette volume
6. Repeat until you get concordant results, then calculate a mean titre

Question 6

Why are acid-base indicators used?

Answer 6

To detect when a reaction reaches completion, usually by the presence of a colour change

Question 7

What are concordant results?

Answer 7

Titres that are within 0.1 cm^3 of each other

Question 8

What are some common potential hazards and risks in the lab and how can you control them?

Answer 8

• Bunsen burner risks burns so keep it away from flammable chemicals and from the edge of the desk
• Chemicals may: be an irritant or corrosive, causing irritation to skin, eyes or lungs; be toxic; be flammable. So handle them with care and while wearing gloves. Wear eye protection keep away from the edge of the desk and from an open flame. Also don’t ingest them
• Glassware like beakers & test tubes may break or cut someone so handle with care and keep away from the edge of the desk