C4 - Producing and identifying products in chemical reactions (FAREEHA)

Question 1

What are the properties of alkali metals?

Answer 1

• shiny when freshly cut
• soft (softer going down)
• solid at Room Temp
• good conductor

Question 2

What do alkali metals form when they react with water?

Answer 2

Alkali metals react in water to form alkaline solutions.

Question 3

What colour are the ionic compounds formed from alkali metals?

Answer 3

white or colourless ionic compounds

Question 4

Trends in …… for alkali metals. (GOING DOWN THE GROUP)
- Reactivity
- MP / BP
- Density

Answer 4

Reactivity increases (going down the group);
valence electrons are further from the nucleus, so it is easier to loose - weaker electrostatic forces of attraction

Melting point decreases (going down the group);
more shells, so delocalised electrons are further from the nucleus - weaker electrostatic forces of attraction

Density increases (going down the group);
more shells, denser

Question 5

Explain how Lithium, Sodium, Potassium react in water.

Answer 5

• Lithium fizzes steadily and slowly disappears.
• Sodium melts to form a silvery ball, fizzes vigorously and then quickly disappears.
• Potassium immediately ignites, burns with a lilac flame and very quickly disappears.

Question 6

What are the properties of the halogens?

Answer 6

• Brittle
• Poor conductors
• Diatomic molecules
  Halogens can displace halides in solution

Question 7

What do fluorine, chlorine, bromine and iodine look like at RM?

Answer 7

Fluorine - pale yellow gas
Chlorine - green gas
Bromine - orange-brown liquid
Iodine - shiny grey-black crystalline solid

Question 8

What do halogens and metals react to form?

Answer 8

Halogen + metal -> salt

Question 9

Trends in …… for the halogens. (GOING DOWN THE GROUP)
- Reactivity
- MP / BP
- Density

Answer 9

Reactivity decreases (going down the group);
more shells, valence shell further from nucleus, so harder to gain electrons - weaker electrostatic forces of attraction

Melting point increases (going down the group);
more shells, larger molecules, so the Intermolecular forces of attraction are stronger

Density increases (going down the group);
more shells, denser

Question 10

Describe the properties and trends of the noble gases (GROUP 0)

Answer 10

they are unreactive (no tendency to loose/gain electrons as they already have full outer shells - stable)
their MP and density increases going down the group

Question 11

Describe the properties of the transition metals.

Answer 11

• strong; malleable; shiny when freshly cut
• good conductors
• stronger harder higher MP than group 1
• good catalysts
• less reactive than g1 and g2
• can form 2+ or 3+ charges
• form coloured ionic compounds

Question 12

Describe the general trends in reactivity for metals
and reacting metals with water/dilute acid.

Answer 12

MOST REACTIVE <-> LEAST REACTIVE
group 1 , group 2 , transition metals

metals can react with water or dilute acid if it is more reactive than hydrogen

metal + acid -> salt + hydrogen
metal + water -> metal hydroxide + hydrogen

Question 13

List reactivity series.

Answer 13

Potassium, Sodium, Lithium G1 (Lowest first)
Calcium, Magnesium G2 (lowest first)
Aluminium G3
Carbon G4
Zinc, Iron, Tin, Lead Transition Metals
Hydrogen
Copper, silver, gold, platinum

Question 14

How can you test if Carbon dioxide is present?

Answer 14

bubble the gas through limewater
The Limewater (Calcium hydroxide) will turn cloudy white if Carbon dioxide is present

calcium hydroxide + carbon dioxide -> water + calcium carbonate (White precipitate)

Question 15

How can you test if Chlorine is present?

Answer 15

Chlorine dissolves in water to form acidic solutions and bleaches dyes.
1. dampen blue litmus paper
2. hold to container
3. is chlorine is present, the paper will turn from blue to red then white

Question 16

How can you check if hydrogen is present?

Answer 16

hold a lighted splint to the test tube, it will ignite with a squeaky pop if present

Question 17

How can you check if oxygen is present?

Answer 17

hold a glowing splint to the test tube, it will relight if present

Question 18

How does a flame test work?

Answer 18

When metal ions are heated, energy is transferred to their electrons, so they move to higher electron shells. When they move back, energy is transferred to the surroundings as radiation (light).

Question 19

Flame test table

Answer 19

Lithium - Red
Sodium - Yellow
Potassium - Lilac
Calcium - orange red
Copper - green blue

Question 20

Precipitate colour table (Reacting with hydroxide precipitate)

Answer 20

Iron (II) - green
Iron (III) - orange-brown
Copper (II) - blue
Calcium - white
Zinc - white (but dissolves in excess)

Question 21

How can you test for the presence of sulfate ions?

Answer 21

Barium reacts with sulfate ions to produce barium sulfate (white, insoluble precipitate)
1. add a few drops of dilute hydrochloric acid
2. add a few drops of barium chloride solution
if present, white precipitate

Question 22

How can you test for the presence of carbonate ions?

Answer 22

carbonate + hydrogen -> carbon dioxide + water
1. add a few drops of dilute hydrochloric acid
if present, bubbles of gas (CO2) produced

Question 23

How can you test for the presence of halide ions? (and identify them)

Answer 23

1, add few drops of nitric acid
2. few drops of silver nitrate solution (PRECIPIATE COLOUR)
Chloride - white
Bromide - cream
Iodide - yellow

Question 24

what is an instrumental method of analysis?

Answer 24

It relies on a machine to carry out an analysis of a substance

Question 25

what are the advantages of instrumental methods of analysis?

Answer 25

• sensitivity (can analyse very small amounts)
• accuracy (accurate, can be calibrated)
• speed (fast analysis 24/7)

Question 26

How can you read a chromatogram?

Answer 26

• peaks represent different components
• the area under the peak is the relative amount
• the retention time is individual to each substance like Rf

Question 27

What does a mass spectrometer do?

Answer 27

measures masses of atoms and molecules, and analyses relative amounts of different isotopes of elements and their structure

Question 28

how to read mass spectra?

Answer 28

each peak reps fragment of molecule
peak on far right - molecular ion
the mass to charge ratio of the molecular ions equals Mr of substance