4: Inorganic + The Periodic Table

Question 1

Lithium (Li+) flame color

Answer 1

Scarlet red

Question 2

Sodium (Na+) flame color

Answer 2

Bright yellow

Question 3

Potassium (K+) flame color

Answer 3

Lilac

Question 4

Rubidium (Rb+) flame color

Answer 4

Red

Question 5

Caesium (Cs+) flame color

Answer 5

Blue-violet

Question 6

Magnesium (Mg+2) flame color

Answer 6

No visible flame

Question 7

Calcium (Ca+2) flame color

Answer 7

Brick-red

Question 8

Strontium (Sr+2) flame color

Answer 8

Red

Question 9

Barium (Ba+2) flame color

Answer 9

Apple-green

Question 10

What is the trend in ionization energy down group 2?

Answer 10

Ionization energy decreases

Question 11

What is the reason for the trend in ionization energy down group 2?

Answer 11

(Decreases) because:
- Electrons are held further from the nucleus, lower attraction
- More shielding, lower attraction
- Electrons are therefore easier to remove

Question 12

What is the trend in reactivity down group 2?

Answer 12

Reactivity increases down group 2

Question 13

What is the reason for the trend in reactivity down group 2?

Answer 13

(Increases) because:
- Electrons are held further from the nucleus, lower attraction
- More shielding, lower attraction
- Electrons require less energy to remove

Question 14

Group 2 metal + Oxygen ?

Answer 14

Burn readily in oxygen, forming XO compounds

Question 15

What precautions are needed and why when using Mg ribbon?

Answer 15

MgO forms slowly when Mg metal is exposed to oxygen, so the ribbon needs to be cleaned off to remove MgO which reacts differently to pure Mg

Question 16

Group 2 metal + Chlorine?

Answer 16

Form the compound XCl2

Question 17

Mg + steam ?

Answer 17

Forms MgO and hydrogen gas

Question 18

Mg + warm water ?

Answer 18

Forms Mg(OH)2 and hydrogen gas

Question 19

Ca, Sr, Ba + cold water ?

Answer 19

Form hydroxides and hydrogen gas

Question 20

What would be observed when a group 2 metal reacts with water?

Answer 20

• Effervescence
• Metal dissolves
• Solution heats up
• Solution turns alkaline

Question 21

Group 2 oxide + water?

Answer 21

Form hydroxides, increasing in pH as you go down the group

Question 22

What is the trend in group 2 hydroxides ?

Answer 22

Increase in pH going down the group because more OH- ions are free in solution

Question 23

Group 2 hydroxide + (dilute) acid?

Answer 23

Form a salt and water

Question 24

Group 2 hydroxide + acid?

Answer 24

Form a salt and 2 water molecules

Question 25

What is the trend in solubility of group 2 hydroxides?

Answer 25

Become more soluble down the group
- Mg classed as insoluble
- Ca reasonably soluble
- Ba very soluble

Question 26

What is the trend in solubility of group 2 sulfates?

Answer 26

Become less soluble down the group
- BaSO4 is the least soluble

Question 27

Group 2 oxide + acid?

Answer 27

Form hydroxides and water

Question 28

Group 2 hydroxide + acid?

Answer 28

Form hydroxides and 2 water molecules

Question 29

What is the trend in solubility of group 2 hydroxides?

Answer 29

Solubility increases down the group

Question 30

What is the trend in solubility of group 2 sulfates?

Answer 30

Solubility decreases down the group

Question 31

What is thermal decomposition?

Answer 31

The use of heat to break down a reactant into more than one product

Question 32

What is thermal stability?

Answer 32

The ease of which a compound thermally decomposes. If a compound has high thermal stability, it will not decompose as easily

Question 33

What is the trend in thermal stability of group 1 + 2 carbonates?

Answer 33

Thermal stability increases going down the group

Question 34

What is the reason for the trend in thermal stability of carbonates?

Answer 34

Cations with a smaller charge/density ratio have less polarizing power and do not distort the carbonate ion’s bonding electrons as easily. The C-O bond is less weakened and needs more heat energy to be broken

Question 35

Do group 1 or group 2 carbonates thermally decompose more easily?

Answer 35

Group 2 carbonates are less thermally stable overall because they have larger charge-density ratios than their corresponding group 1 carbonate

Question 36

How do you investigate thermal decomposition of carbonates?

Answer 36

It gives off CO2 gas, so by using lime water and timing how long it takes for it to become permanently cloudy, thermal stability can be compared

Question 37

What is the trend in thermal stability of group 2 nitrates?

Answer 37

Thermal stability increases down the group

Question 38

What is the reason for the trend in thermal stability of group 2 nitrates?

Answer 38

Cations with a smaller charge/density ratio have less polarizing power and do not distort the nitrate ion’s bonding electrons as easily. The N-O bond is less weakened and needs more heat energy to be broken

Question 39

How do you investigate the thermal decomposition of nitrates?

Answer 39

• Brown gas will evolve
• Nitrate solid melts into a colorless solution, then re-solidifies

Question 40

What is the reason behind flame colors?

Answer 40

Electrons are excited by the heat energy and move to a higher energy level. Upon their return to their original energy level, energy is released, which is seen as light energy (the flame color)

Question 41

How do you investigate flame colors?

Answer 41

Clean a nichrome wire with hydrochloric acid and dip into the solution of cations. Hold over the Bunsen flame and observe the color of the flame