Topic 4: Inorganic Chemistry (Group 7)

Question 1

Trends in melting and boiling points down the group for halogens

Answer 1

• Increases

- As there are greater London forces

Question 2

Equations for changes of state

Answer 2

Br2(l) ➝ Br2(g) (brown vapour)

I2(s) ➝ I2(g) (sublimation)

Question 3

Trends in electronegativity down the group 7

Answer 3

• Decreases as there is more electron shielding
• Distance from the nucleus and the bonding pair of electrons increase therefore less attraction to the pair of electrons in a covalent bond (less electronegative)

Question 4

Trends in reactivity down the group 7

Answer 4

• Decreases down the group because of a decrease in electronegativity
• Explain using the same factors for electronegativity
• Distance from nucleus and Shielding

Question 5

Halogen/Halide displacement reactions ( the more reactive replaces the least reactive)

Answer 5

Halogens can displace….
Cl: Br, I
Br: I
I: none

Question 6

What needs to be done to an aqueous halide solution to see the colours easier? What are the colours visible?

Answer 6

-Add cyclohexane
-Halogens are more soluble in cyclohexane
Cl: light green
Br: red-brown
I: Purple

Question 7

Chlorine displacing bromine & Bromine displacing iodine

Answer 7

Cl2 + 2NaBr ➝ 2NaCl + Br2

Br2 + 2I- ➝ I2 + 2Br-

Question 8

Why is chlorine the most reactive out of Br and I?

Answer 8

• Smaller atom so greater attraction from the nucleus

- Smaller amount of orbitals therefore less repulsion of the incoming electron

Question 9

Disproportionation reactions for Chlorine

Answer 9

Chlorine with Water

Chlorine with COLD and HOT alkali

Question 10

Chlorine with Water (used for water treatment)

Answer 10

Cl2 + H2O ➝ HCl + HClO

Question 11

Chlorine with COLD alkali (forms bleach (NaClO))

Answer 11

Cl2 + 2NaOH ➝ NaCl + NaClO + H2O

Question 12

What is the formula for the two bleaches?

Answer 12

NaClO (Cold alkali)

NaClO3 (Hot alakli)

Question 13

Chlorine with HOT alkali (forms bleach (NaClO3))

Answer 13

3Cl2 + 6 NaOH ➝ 5NaCl + NaClO3 + 3H2O

- Chlorine + sodium hydroxis -> sodim chloride + sodium chlorate(V) + water

Question 14

Do Br & I react in similar ways with water and alkali?

Answer 14

YES just replace the Cl with the halogen

Question 15

What are the 3 possible reduction products when halides react with conc Sulfuric Acid?

Answer 15

• SO2 (+4)
• S (0)
• H2S (-2)

Question 16

NaCl + H2SO4 observation

Answer 16

-misty fumes (HCL)

Question 17

NaBr + H2SO4 observation

Answer 17

• HBr (misty fumes)
• Br2 (brown vapour)
• SO2 (colourless gas with a choking smell)

Question 18

NaI + H2SO4 observation

Answer 18

• HI (misty fumes)
• I2 (purple fumes or black solid)
• SO2 (colourless gas with chocking smell)
• S (yellow solid)
• H2S (colourless gas with rotten egg smell)