Required Practicle 5 Rates Of Reaction Disappearing Cross

Question 1

What does the disappearing cross experiment find

Answer 1

The effect of concentration on rate of reaction

Question 2

What is a reproducible measurement

Answer 2

A measurement is reproducible if it can be repeated by another person using a different technique or equipment and still get the same result

Question 3

Problem with disappearing cross experiment

Answer 3

People have different eyesight so some take longer for the cross to disappear than others.

However by using the same sized printed cross the problem shouldn’t be to great

Question 4

What is a hypothesis

Answer 4

Proposal that could be explain a fact or observation and must be testable

Question 5

The disappearing cross reaction

Answer 5

Sodium thiosulphate solution + hydrochloric acid goes to sulfur

Question 6

What does the product sulphur do in the experiment

Answer 6

As it is a solid itmakes that solution go cloudy ( turbidity)

We can use this to see how long the reaction takes to finish, as once you can’t see the cross the reactions done

Question 7

Method

Answer 7

Using a measuring cylander put 10 cm³ of sodium thiosulphate in a conical flask

Place flask onto a printed black Cross

Add 10 cm³ of hydrochloric acid into conical flask

Swirl solution and start stopwatch

Look down through top of the flask as after a certain time the solution will turn cloudy

We stop the clock when we can no longer see the cross

Then carry out the experiment again using lower concentrations of sodium thiosulphate solution

Repeat the experiment 2 again and find a mean for each concentration