Topic C4- Predicting and Identifying Reactions and Products

Question 1

What are group 1 metals called?

Answer 1

Alkali metals.

Question 2

What are the group 1 metals?

Answer 2

Lithium, Sodium, Potassium, Rubidium, Caesium and Francium.

Question 3

Why do all group 1 elements have similar chemical properties?

Answer 3

They all have 1 outer electron.

Question 4

What physical properties do all alkali metals have?

Answer 4

• Low melting points and boiling points (compared with other metals)
• Low density- lithium, sodium and potassium float on water.
• Very soft- they can be cut with a knife.

Question 5

How can you test for the presence of group 1 metals?

Answer 5

Flame tests.

Question 6

Why are group 1 metals very reactive?

Answer 6

• the group 1 metals readily lose their single outer electron to form a 1+ ion with a stable electronic structure.
• The more readily a metal loses its outer electron, the more reactive it is- so group 1 metals are very reactive.
• As the periods decrease in group 1, the alkali metals get more reactive.
• The outer electron is more easily lost because it is further from the nucleus (atomic radius is larger)
• so it is less strongly attracted to the nucleus and less energy is needed to remove it.

Question 7

What happens when alkali metals are put in water?

Answer 7

• they produce hydrogen gas and hydroxide of the metal.

e. g. 2Na + 2H2O -> 2NaOH + H2

Question 8

What are group 7 elements called?

Answer 8

Halogens.

Question 9

Why do group 7 elements all have similar chemical properties?

Answer 9

They all have 7 electrons in their outer shell.

Question 10

What is a diatomic molecule?

Answer 10

Diatomic molecules are molecules composed of only two atoms, of the same or different chemical elements.

Question 11

What happens to halogens as you descend the periods?

Answer 11

• The melting points and boiling points of the halogens increase.
• They halogens become less reactive- it gets harder to attract the extra electron to fill the outer shell when it’s further away from the nucleus. (Atomic radius is larger.)

Question 12

What does a reaction between halogens and alkali metals form?

Answer 12

They form salts- called metal halides.

Question 13

What is a displacement reaction?

Answer 13

Where a more reactive element displaces a less reactive element from a compound.

Question 14

How can you use displacement reactions to show reactivity trends?

Answer 14

1) Start by measuring out a small amount of halide salt solution in a test tube.
2) Add a few drops of a halogen solution. Shake tube gently.
3) If you see a colour change, then a reaction has happened- the halogen has displaced the halide ions from the salt.
4) Repeat the process using different combinations of halide salt and halogen.

Question 15

What is the name given to Group 0 elements?

Answer 15

Noble Gases.

Question 16

What are the elements in group 0?

Answer 16

Helium, Neon, Argon, Krypton, Xenon and Radon.

Question 17

What are the properties of the noble gases?

Answer 17

1) All of the elements of group 0 are colourless gases at room temperature.
2) The noble gases are all monatomic- made up of single atoms.
3) They’re inert- they don’t react with much at all.
4) They have a full outer shell, so they don’t easily gain or lose electrons.
5) They are non-flammable.

Question 18

What are the trends in group 0 elements as you descend down the periods?

Answer 18

The boiling points, melting point, and density all increase as you go down the periods.

Question 19

What are the typical metallic properties of transition metals?

Answer 19

They are:

• hard
• shiny
• strong
• conduct heat
• conduct electricity
• high melting and boiling points (except mercury)
• high densities.
• have more than one ion (e.g. Fe2+, Fe3+)
• Their compounds are very colourful.
• relatively unreactive.

Question 20

Which transition metal is used as a catalyst in the Haber Process?

Answer 20

Iron.

Question 21

Which transition metal is used as a catalyst in the Contact Process?

Answer 21

Vanadium Pentoxide.

Question 22

How do metals reacting with acids tell you about their reactivity?

Answer 22

1) The easier it is for a metal to lose its outer electrons and form a positive ion, the more reactive it will be.
2) The more reactive the metal, the faster the reaction will go.
3) Very reactive metals (Mg) will fizz vigorously, less reactive metals (Zn) will bubble a bit, and unreactive metals (Cu) will not react with dilute acids at all.
4) You can show that hydrogen is forming using the burning splint test. The louder the squeaky pop, the mor ehydrogen has been made in the time period and the more reactive the metal is.
5) Speed of reaction is indicated by the rate at which the bubbles of hydrogen are given off- the faster the bubbles form, the faster the reaction and the more reactive the metal. (*gas syringe to measure volume of gas given off at regular intervals.)

Question 23

Complete the formula:

metal + water –>…:

Answer 23

metal + water –> metal hydroxide + hydrogen.

Question 24

Name the metals in the reactivity series, from the most reactive to the least reactive:

Answer 24

Potassium
Sodium 
Calcium
Magnesium
Aluminium
Zinc
Iron
Copper
Silver

Question 25

What happens if you put a more reactive metal into a solution of a less reactive metal salt?

Answer 25

The more reactive metal will replace the less reactive metal in the salt.

Question 26

What happens if you put a less reactive metal into a solution of a more reactive metal salt?

Answer 26

Nothing will happen- the more reactive metal is already in the salt.

Question 27

How can you test for carbon dioxide?

Answer 27

Use limewater:

• bubble co2 through limewater
• if gas is co2, then the limewater will turn cloudy

Question 28

How can you test for hydrogen?

Answer 28

• Hydrogen makes a squeaky pop with a lighted splint.

- The noise comes from the hydrogen burning with the oxygen in the air to form water.

Question 29

How can you test for oxygen?

Answer 29

Use a glowing splint- if oxygen is present than it will relight a glowing splint.

Question 30

How can you test for chlorine?

Answer 30

Using a damp blue litmus paper:

• hold piece of damp blue litmus paper over gas.
• if gas is chlorine, it will bleach the litmus paper, turning it white.
• it may also turn red at first- that is because a solution of chlorine is acidic.

Question 31

How can you test for halide ions?

Answer 31

Using Silver Nitrate Solution:

• To test for Cl- ions, Br- ions or I- ions, add some dilute nitric acid
• followed by a dew drops of silver nitrate.

The results should show:

• chlorine gives a white precipitate of silver chloride.
• bromide gives a cream precipitate of silver bromide.
• iodide gives a yellow precipitate of silver iodide.

Question 32

How can you test for carbonates?

Answer 32

Using Hydrochloric Acid:

• to test for carbonate ions, add some barium chloride solution.
• if there are carbonate ions present, this will produce a white precipitate of barium carbonate.
• then you add some dilute hydrochloric acid.
• if there are carbonate ions present, the mixture will fizz (carbonate reacts with acid to produce carbon dioxide).
• if you collect the gas and pas it through limewater, the limewater should turn cloudy.
• once all the barium carbonate has reacted, there will be a colourless solution containing Ba2+ ions.

Question 33

How can you test for sulfate ions?

Answer 33

Using Barium Chloride Solution:

• add some barium chloride solution.
• if there are sulfate ions in the solution, a white precipitate will form.
• then add dilute hydrochloric acid
• barium sulfate will not react with the dilute hydrochloric acid, so white precipitate will not dissolve (this is how you know you have sulfate ions and not carbonate ions.)

Question 34

How can you identify metal ions in a compound?

Answer 34

Using flame tests:
Compounds will produce a characteristic colour when heated in the flame.

To carry out a flame test, clean a nichrome wire loop by dipping it in hydrochloric acid and rinse it with deionised water.

Dip the wire loop into sample of metal compound and put the loop in the clear blue part of the Bunsen Burner.

The colour for each metal:
Lithium- crimson red flame
Sodium- yellow flame
Potassium- lilac flame
Calcium- brick red flame
Copper- blue-green flame.

Question 35

What are the advantages for instrumental analysis methods?

Answer 35

• they are very sensitive: detect even the smallest amounts of a substance.
• they are fast
• they are very accurate- don’t involve human error, as manual analysis does.

Question 36

What are some examples of instrumental analysis?

Answer 36

• Infrared Spectroscopy
• Ultraviolet Spectroscopy
• Gas Chromatography
• Mass Spectrometry