Risk Assessments and Errors

When testing for metal ions with NaOH (aq), the solution can be ^^**corrosive**^^ and extremely dangerous to eyes at a concentration of 0.5moldm^-3+.

How can you reduce this risk?

• Use a lower concentration

• Wear eye protection

When testing for organic compounds by heating acidified potassium dichromate(VI), many of the organic molecules are ^^**flammable**^^.

How can you reduce this risk?

* Heat with a water bath instead of a Bunsen burner

In the nitration of benzene, benzene is a ^^**carcinogen**^^.

How can you reduce this risk?

* Use a different aromatic compound that is a low hazard (eg methylbenzene)

When testing solid halides with concentrated sulfuric acid, the concentrated sulfuric acid is ^^**very corrosive**^^.

How can you reduce this risk?

* Wear gloves

When testing reaction kinetics in sodium thiosulfate + acid reaction, ^^**toxic**^^ sulfur dioxide ^^**gas**^^ is produced.

How can you reduce this risk?

• Do the experiment in a fume cupboard

• Do the reaction on a very small scale to minimise amount of gas produced

How can you find experimental error as a percentage?

(Real answer - experimental answer/ Real answer) x100

Does experimental error need to be positive or negative?

No, just put the value

What does it mean if experimental error is higher than apparatus error?

Result is still accurate

What makes a result inaccurate?

If experimental error is greater than apparatus error

How do you find the apparatus uncertainty for a normal measurement?

(margin of error/ quantity measurement) x 100

How do you find the apparatus uncertainty for a change in something? Eg temp, mass

2 x (margin of error/ quantity measured) x 100

How can you find total apparatus uncertainty?

Add together the apparatus uncertainties of all equipment used