C8

Question 1

Tests for positive ions(cations)

Answer 1

Flame tests

Precipitate with sodium hydroxide

Question 2

Tests for negative ions(anions)

Which ions

Answer 2

Hallides

Carbonates co3

Sulfates so4

Question 3

Identifying a half-life ion and what does the precipitate colour tell us
Cl. Br l

Answer 3

Add couple drops of nitric acid
Followed by a couple drops of SILVER NITRATE (agno3)
AgCl-white.
AgBr-cream. Solids
AgI-yellow.
As you go down g7 precipitate gets darker

Question 4

Testing for carbonates (CO3)

Answer 4

Add dilute acid

If present CO2 gas is released + limewater turns milky

Question 5

Testing for sulfates
+
Positive results

Answer 5

Add couple drops of HCl
Followed by couple drops of barium chloride (BaCl2)
Positive results =white precipitate

Question 6

Precipitate with sodium hydroxide

Answer 6

Metal ions form a precipitate (insoluble metal hydroxide)
When SODIUM HYDROXIDE SOLUTION is added
Transition metals produce precipitates

Question 7

Instrumental methods (flame emission spectroscopy) advantages

Answer 7

• accurate (close to true value)
• sensitive (can detect small amounts)
• rapid(quick)
• only small sample needed
• provide quantitative data-measure conc of substance

Question 8

Flame emission spectroscopy what happens

Answer 8

A SAMPLE is put into a FLAME and the LIGHT GIVEN OUT is passed through a SPECTROSCOPE

Output is a LINE SPECTRUM that can be used to identify metal ions+measure their conc

Question 9

Colour of precipitate
Calcium - calcium hydroxide
Aluminum -aluminum hydroxide
Magnesium -magnesium hydroxide

Answer 9

Calcium hydroxide-white
Aluminium hydroxide-white but clear with excess NaOH
Magnesium hydroxide-white

Question 10

Precipitates of
Cu 2+
Fe 2+
Fe 3+

Answer 10

Cu 2+-blue
Fe 2+-green
Fe 3+-brown

Question 11

How do we know a substance is pure

Answer 11

The boiling or melting point

A pure substance melts and boils at SPECIFIC TEMPERATURE

(Straight lines)

Question 12

How can we tell a substance is impure

Answer 12

Lowers mp
Increases bp
RANGE OF TEMPS
(Wobbly line)

Question 13

Formulation is

Answer 13

A useful mixture with specific purpose

Eg paint,fuel,medicine,alloys,fertilizer,food, cleaning products

Question 14

Unadulterated is

Answer 14

A substance with nothing added to it
In its natural state

Eg milk,fresh orange

Question 15

Chromatography is used to

Answer 15

Separate mixtures + identify substances

Question 16

What is a solvent front

Answer 16

The distance a solvent (water) moves up the page

Question 17

Control variables of the start line in chromatography

Answer 17

WATER level must NOT be ABOVE the line or ink will dissolve

Must be drawn in PENCIL pen ink will dissolve in water or run up the page

Question 18

Stationary phase is
+
What happens if a substance is more attracted to the stationary phase

Answer 18

The paper

Substance will not move far up the paper

Question 19

Mobile phase is

+what happens if a substance is more attracted to the mobile phase

Answer 19

The solvent

Substance will move further up water

Question 20

Rf value is calculated by

Answer 20

Distance moved by substance/distance moved by solvent

Units-cm or mm

Rf is always over 1

Question 21

Conducting flame tests

Has to have 1 metal ion in sample, if a mixture then flame colour is masked

Answer 21

LOOP CLEANED by dipping in HCL acid and holding it in a BLUE BUNSEN FLAME until it burns with NO COLOUR

DIPPED IN SAMPLE +PUT IN BLUE FLAME

Observe and RECORD FLAME COLOUR

Question 22

Flame colour 
Lithium ions
Sodium ions
Potassium ions
Calcium ions
Copper ions

Answer 22

Li-red
Na-yellow
K-lilac
Ca-orange/red
Cu-green