Titration

Question 1

What must you wash the burette & pipette with?

Answer 1

A small amount of the solution they’re going to measure

Question 2

What are the 4 steps of a titration calculation?

Answer 2

1. Write the balanced equation
2. Start with the substance you’re told the most about & calculate the number of moles
3. Look at the equation for the ratio with the substance asked about hence work out the number of moles for this substance
4. Convert from moles to what you are asked about in the question (eg: concentration or mass)

Question 3

What is a standard solution?

Answer 3

A solution whose concentration is accurately known.

Question 4

What are the 9 steps to make a standard solution?

Answer 4

1. Work out how many moles of solute you need (use moles=concentration x volume)
2. Work out how many grams of solute is needed using the formula mass = moles x molar mass
3. Carefully weigh out this mass of solute - first weigh the beaker, note the weight, then add the correct mass
4. Add a small amount of distilled water to the beaker and stir until all the solute has been dissolved
5. Tip the solution into a volumetric flask - make sure it’s the right size for the volume you’re making. Use a funnel to make sure it all goes in
6. Rinse the beaker and stirring rod with distilled water and add that to the flask too, this ensures there’s no solute clinging to the beaker or rod
7. Now top up the flask to the correct volume (250cm^3) with more distilled water. Make sure the bottom of the meniscus reaches the line - when you get close to the line use a pipette to add water drop by drop. If you go over the line, you’ll have to start all over again
8. Stopper the bottle and turn it upside down a few times to make sure it’s all mixed
9. Check the meniscus again and add a drop or two if necessary

Question 5

Should you make your standard solution, more dilute, more concentrated or of a similar concentration to the solution you’re titrating against?

Answer 5

A similar concentration to the solution you’re titrating against

Question 6

How do you make standard solutions of different concentrations from a solution of known concentration?

Answer 6

First divide the concentration you want by the concentration you have, then multiply by the volume you want. This gives you the volume of concentrated solution to use.
Then accurately measure out this volume of solution and transfer it into a volumetric flask - don’t use a balance, instead use a pipette or burette, then top up the solution to the required volume with distilled water in the volumetric flask

Question 7

What’s the formula for finding the volume to use from the volume required and concentration?

Answer 7

Vol. To use = final conc/initial conc x vol required