Chemical analysis

Question 1

What color flame does lithium ion produce

Answer 1

Crimson flame

Question 2

What color flame does sodium ion produce

Answer 2

Yellow flame

Question 3

What color flame does potassium ion produce

Answer 3

Lilac flame

Question 4

What color flame does calcium ion produce

Answer 4

Orange-Red flame

Question 5

What color flame does Copper ion produce.

Answer 5

Green flame

Question 6

What are two problems with flame tests?

Answer 6

• The color of the flame can be difficult to distinguish. This could happen due to a low concentration of the metal compound.
• Another reason is the sample could contain a MIXTURE of ions which mask the color of the flame

Question 7

What is a better test than a flame test

Answer 7

A flame emission spectroscopy

Question 8

How does an FES work

and the purpose

Answer 8

A sample of the metal ion in solution is placed in a flame

The light given out is then passed into a machine called a spectroscope

The spectroscope converts the light into a line spectrum

Since the positions of the lines in the spectrum are specific for a given metal ion.

So we can use this to identify the metal ion in the sample.

Question 9

What two things does FES do

Answer 9

To identify the metal ion in the sample.

Tells us the concentration of the metal ion.

Question 10

Iron (III) Fe3+ions precipitates

Answer 10

Brown

Question 11

Copper (II) Cu2+ ion precipitates

Answer 11

blue

Question 12

Iron (II) Fe2+ ion precipitates

Answer 12

Green

Question 13

Magnesium Mg2+ ion precipitates

Answer 13

White

Question 14

Calcium, Ca2+ ion precipitates

Answer 14

White

Question 15

Aluminium Al3+ precipitate

Answer 15

White

Question 16

How to distinguish between Aluminium ions from calcium ions and magnesium ions.

Answer 16

Add extra sodium hydroxide the aluminum hydroxide eventually will become colorless

If extra sodium hydroxide is added to calcium and magnesium the solution will not change.

Question 17

What is a formulation

Answer 17

A mixture that has been designed as a useful product

Question 18

Step 1 of testing for a Carbonate ion

Answer 18

Add dilute acid

Question 19

What will happen once Carbonate reacts with dilute acid

Answer 19

Carbon dioxide produced/created
Will see effervescence

Question 20

Chloride ions produce what precipitate. + colour

Answer 20

White precipitate of silver chloride

Question 21

Bromide ions produce what precipitate + colour

Answer 21

Cream precipitate of silver bromide.

Question 22

Iodide ions produce what precipitate + colour

Answer 22

Yellow precipitate of silver iodide

Question 23

What is the formula for the aqueous solution of lime water

Answer 23

calcium hydroxide

Question 24

How to test for carbon dioxide (5)

+ positive result

Answer 24

We test for co2 using limewater (lime water is an aqueous solution of calcium hydroxide)

Draw some of the gas in the test tube containing the possible co2 into a plastic pipette

We then bubble the gas through the limewater

Repeat several times

Positive result = lime water turns cloudy

Negative result = nothing happens

Question 25

How do we test for chlorine (3)

+ positive result

Answer 25

To test for chlorine we insert damp litmus paper into the mouth of the test tube.

Positive result: Chlorine bleaches the litmus paper and turns it white

Question 26

Testing for sulfate ions (3)

Answer 26

Add a few drops of HCl and add a few drops of dilute barium chloride

A white precipitate will form

Question 27

Explain why in a test for sulfate ions, the sample is acidified with hydrochloride acid first. (3)

Answer 27

Carbonate ions also produce a white precipitate with barium chloride solution. The acid reacts with any carbonate ions present. This removes them, so stopping them giving a false positive result

Question 28

How to test for halide ions (2)

Answer 28

Add a few drops of dilute nitric acid to the sample

Add a few drops of dilute silver nitrate solution