C12- Chemical analysis

Question 1

What is a pure substance?
Example?
What is a mixture?
Example?

Answer 1

A substance that only contains one substance
Pure water (just H2O)
Two or more substances that aren’t chemically combined
Air

Question 2

Key fact about pure substances?
Key fact about impure substances?

Answer 2

They have specific melting and boiling points and will melt/boil at exactly that temp
They will melt/boil over a range of temps

Question 3

What are fixed points?

Answer 3

The melting and boiling points of a substance

Question 4

How does rock salt help roads become less slippery?
How does salt help when cooking?

Answer 4

Lowers the melting point of water, the impurities disrupt the structure of ice, weakens intermolecular forces, less ice
Raises the boiling point of water, food cooks more quickly

Question 5

Formulation?
Example?

Answer 5

A mixture designed to create a useful product. Measured in fixed proportions to create specific properties
Paint, toothpaste

Question 6

Paper chromatography definition?

Answer 6

The separation of substances using a solvent which carries the mixture through paper

Question 7

Chromatography
Stationary phase?
Mobile phase?

Answer 7

The fixed surface where the process takes place
The solvent that carries the dissolves substances

Question 8

From a chromatogram
What dyes are in the mixture?
How many substances it contains?

Answer 8

Contain dyes that travelled the same distance and have the same colour
The number of spots in the same column

Question 9

How to calculate the Rf value and what is it?

Answer 9

Retention factor = distance travelled by substance / distance travelled by solvent

Question 10

What does a higher Rf mean?
What does a lower Rf mean?
When will Rf change?

Answer 10

Substance is more attracted to solvent
Substance is more attracted to paper
The solvent and paper used

Question 11

Paper chromatography method?

Answer 11

-Draw pencil line 2 cm from bottom of the filter paper
-Put a small dot of each dye spaced apart on the pencil line and label
-Place small amount of water in a beaker
-Place filter paper in the solvent so the water is just below the dyes
-Leave for 5 mins, label solvent front and measure using a ruler, dry
-Calculate Rf values using Rf= distance moved by substance / distance moved by solvent

Question 12

Test for hydrogen?
Oxygen?
Carbon dioxide?
Chlorine?

Answer 12

Lit splint–>squeaky pop sound
Glowing splint–>splint relights
Bubble through limewater–>turns cloudy
Damp litmus paper–>turns white/bleached