3- Analysis And Synthesis

Question 1

What colour does each metal ion produce when flame tested?

Group1 and 2 elements

Answer 1

Lithium - red
Sodium - yellow
Potassium - lilac
Calcium - red
Barium - green

Question 2

What happens when sodium hydroxide is added to solutions of metal ions and why?

Answer 2

A precipitate of metal hydroxide is formed - hydroxides of metals what +2/3 charges are insoluble in water

Question 3

What do aluminium, calcium and magnesium ions form?

Answer 3

White precipitates

When sodium hydroxide is added, aluminium hydroxide dissolves

Question 4

What is the colour of:

1) copper (II)
2) iron (II)
3) iron (III)

Answer 4

1) blue
2) green
3) brown

Question 5

What is the test for negative carbonate ions?

Answer 5

Add dilute hydronic acid to the substance to see if it fizzes
If it fizzes and turns limewater milky it contains carbonate ions

Question 6

What is the test for negative halide ions?

Answer 6

Add dilute nitric acid and then silver nitrate solutions. Check for precipitates:
Chloride ions give a white precipitate
Bromide ions give a cream precipitate
Iodide ions give a yellow precipitate

Question 7

What is the test for negative sulphate ions?

Answer 7

Add dilute hydrochloric acid and then barium chloride solution
If a white precipitate forms, sulphate ions are present

Question 8

What does titration find?

Answer 8

The volume of solutions that react exactly when solutions of acid and alkali react to form a salt and water

Question 9

What equipment is used during titration and how?

Answer 9

A pipette - measure the volume of alkali put in the conical flask
An indicator - added to the alkali
A burette - filled which acid which is added gradually to the conical flask

Question 10

How do you find the results from titration?

Answer 10

When the indicator changes colour the end point has been reached
The volume of acid used is found by subtracting the final from the initial burette readings

Question 11

What is a solutions concentration measured in?

Answer 11

Grams per decimetre cubed (g/dm3)

Moles per decimetre cubed (mol/dm3)

Question 12

What are the steps in titration calculations?

Answer 12

Write out or balance the equation for the reaction
Multiply the concentration and volume of the known substance and then divide it by 1000
Check for big numbers in front in the equation and change using ratio
Rearrange the equation to make what you want the subject and then carry out the equation to find the answer

Question 13

What are the purposes for analysing substances?

Answer 13

Environmental, medical and forensic investigations

Question 14

What are the methods for analysing substances?

Answer 14

‘Wet chemistry’ methods (what we do)

Instrumental methods such as gas chromatography

Question 15

What’s the difference between qualitative and quantitative methods?

Answer 15

Qualitative is used to find out if a substance is in a sample
Quantitative is used to find out how much of a substance is in a sample

Question 16

What does a reversible reaction mean?

Answer 16

Products can react together to make the reactants again

Question 17

What is equilibrium?

Answer 17

When the rate of forward reaction is equal to the rate of the reverse reaction. Both reactions continue bit the amount of both reactant and product remains constant

Question 18

In industry, why is changing the conditions of a reactant or product important?

Answer 18

When conditions are changed, the system attempts to reach equilibrium again - trying to cancel out the change, this can be used to industries advantage to make reversible reactions more efficient

Question 19

If you wanted more products formed, how would you alter the reversible reaction?

Answer 19

Increase the pressure or concentration

Question 20

What happens when the forward reaction is exothermic in terms of temperature altering?

Answer 20

An increase in temperature decreases the amount of product formed
A decrease in temperature increases the amount of product formed

Question 21

What happens when the forward reaction is endothermic in terms of temperature altering?

Answer 21

An increase in temperature increases the amount of product formed
A decrease in temperature decreases the amount of product formed

Question 22

What is the hater process used for?

Answer 22

To manufacture ammonia (can be used to make fertilisers)

Question 23

What is the hater process?

Answer 23

Nitrogen (from the air) and hydrogen (from natural gas) are purified and mixed in the correct proportions which are then passed over an iron catalyst at high temperature and pressure.

The reaction is reversible (yield of ammonia only 15%)

Question 24

What happens the the ammonia and other gasses that come out of the reactor in the hater process?

Answer 24

They are cooled so the ammonia condenses. Liquid ammonia is separated from the unreacted gases

Question 25

What needs to be considered when deciding the pressure of an industrial reaction?

Answer 25

Cost of the pressure

Yield of the pressure

Question 26

What needs to be considered when deciding the temperature of an industrial reaction?

Answer 26

Time it takes

The yield

Question 27

How can positive ions be identified?

Answer 27

Using the flame test or using sodium hydroxide