Chemical analysis

Question 1

What is the difference between a pure substance and a mixture

Answer 1

Pure - a substance which consists of a single element or compound
Mixture - two or more different substances, not chemically bonded

Question 2

How can you tell the difference between a pure substance and a mixture

Answer 2

A pure substance will have a fixed melting point
A mixture will have a range of melting points

Question 3

What is a formulation and what are some examples

Answer 3

A mixture that has been designed as a useful product

Fuels
Medicine
Fertiliser

Question 4

Required practical : Chromatography

What is the method

Answer 4

Pour 1 cm of water into a beaker
Draw a pencil to draw a line 1.5 cm from the bottom of the chromatography paper
Put the solvent on the line using a capillary tube and label it underneath in pencil
Wrap the top of the paper on a splint and hold it together with a paperclip and put into the beaker
Take out the paper once the water reaches ¾ of the paper and let it dry

Question 5

Required practical : Chromatography

What are the phases

Answer 5

Mobile - solvent moving through the paper, carrying different substances with it
Stationary - contained on the paper and doesn’t move through it

Question 6

Required practical : Chromatography

How do you calculate the Rf value

Answer 6

Distance travelled by substance / distance travelled by solvent

Question 7

How do you test for oxygen and what is the expected outcome

Answer 7

Place a glowing splint into the tube

Splint relights

Question 8

How do you test for hydrogen and what is the expected outcome

Answer 8

Place a burning splint into the tube

Create a pop sound

Question 9

How do you test for carbon dioxide and what is the expected outcome

Answer 9

Bubble gas through lime water

Lime water will go from clear to cloudy