RP1: Making Standard Solution and Titrations

Question 1

What is a standard solution?

Answer 1

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 weighing 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 and invert multiple times.

Question 3

What is the weighing by difference technique?

Answer 3

Mass of substance = mass of weighing dish and substance - mass of dish after mass has been transferred

Question 4

What equipment is used to carry out a titration?

Answer 4

• 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 yo add small volumes of one reactant to the other reactant until the reaction has reached 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 the 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 to mix 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 three concordant results and 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 0.1cm3 of each each

Question 8

What are some common practical hazards and risks in the lab?

Answer 8

Bunsen Burner = Burners = Keep away from flammable chemicals and away from the edge of the desk.

Chemicals = Irritant, toxic or flammable = Handle with care and while wearing gloves and eye protections.

Glassware = Breakable = handle with care and keep away from the edge of the desk