ACID BASED TITRATIONS

Question 1

What is a hazard

Answer 1

Anything that has the potential to cause harm or damage

Question 2

What is a risk

Answer 2

The probability of someone being harmed if they are exposed to the hazard

Question 3

What is a standard solution

Answer 3

A solution that you know the concentration of

Question 4

How do you make a standard solution

Answer 4

1. First work out roughly how many moles of solute you need by using the formula

Moles= concentration x volume(cm3)/1000

2. Work out how many grams of solute is needed by using the formula

Mass= moles x molar mass

3. Weigh the weighing vessel and note it down then Carefully weigh out the mass of the solute using the balance
4. Add the solid acid to a beaker containing 100 cm3 of distilled water and stir until all of the solute has dissolved
5. Re weigh the weighing vessel and use this mass alongside the combines mass of the acid + vessel to caluclate the exact mass of acid that has been added
6. Do moles = mass/mr to find out the moles

and then concentration= moles x1000/volume to find conc

7. Tip the solution into a volumetric flask using a funnel
8. Rinse the beaker and stirring rod with distilled water and add that to the flask too to make sure there is no solute clinging
9. Now add distiled water until you get 250 cm3 of solution. Make sure the bottom of the meniscus reaches this line
10. Put a stopper on the bottle and shake

Question 5

What does a pipette do

Answer 5

Measure only one volume of solution

Question 6

What does a burette do

Answer 6

Measures different volumes and lets you add the solution drop by drop

Question 7

Describe the process of carrying out a titration

Answer 7

1. You measure out some alkali of unknown concentration eg NaOH using a pipette and put it into the flask
2. Rinse the burette with some of your standard solution of acid. Then fill it with your standard solution
3. First do a rough titration to get an idea of where your end point is (where the indicator changes colour)
4. Now do an accurate titration. Stop running the acid close to the end point then do it drop by drop
5. Work out the titre ( the volume of acid used to neutralise the alkali)
6. Repeat the titration a few times and calculate a mean using your concordant results ( should be withing 0.1 cm3 of each other )

Question 8

What are titrations used for

Answer 8

Titrations allows you to find out exactly how much acid is needed to neutralise a quantity of alkali

Question 9

What are the two indicators that can be used

Answer 9

1. Methyl orange - turns yellow- red when adding acid to alkali
2. Phenolphthalein - turns red to colourless when adding acid to alkali

Best to put the flask containing the indicator on a white surface to see the color change better