Reactivity Trends

Question 1

How does Atomic Radius, 1st IOnisation energy and Melting Points change down Group 2?

Answer 1

1. More Shells = Larger atoms!
2. Larger atoms = more shells = more sheilding = lower I.E!
3. Weaker metallic bonding = lower melting points!

Question 2

How does reactivity change down Group 2?

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Answer 2

• Will increase, as ionisation energy decreases
• Easier to loose outermost electrons as atomes increase in size!

Question 3

How does alkilinity change down Group 2?

Answer 3

• Down the group, solubility of hydroxides will increase
• pH will increase, as concentration of OH- ions released will increase
• Hence, increase in alkalinity!

Question 4

Use of Group 2 compounds?

Answer 4

1. Ca(OH)2 = Soil Neutralisation
2. Mg/Ca (OH)2 = Stomach Indigestion Tablets

Question 5

Physical Properties of Halogens?

Answer 5

1. Flourine = Yellow Gas, Toxic+Reactive
2. Chlorine = Green Gas, Toxic+Reactive
3. Bromine = Brown Liquid+Orange Vapour
4. Iodine = Grey Crystal Solid+ Purple Vapour Gas

Question 6

Halogen colours in Water and Organic Solvent?

Answer 6

1. Chlorine = Pale Green (both)
2. Bromine = Orange (both)
3. Iodine = Brown in water, Violet in O.S.!

Question 7

How does Boiling Points change down Group 7?

Answer 7

1. Boiling Points increase!
2. Due to more electrons per atom = Greater London Forces in induced d-d interactions
3. more energy required to break the London Forces!

Question 9

What does solution colour indicate about reaction in Halide Displacements?

Answer 9

• Colour = Element being displaced in reaction, from its compound!
• HENCE, NO LONGER IN ION FORM!

Question 10

How does Reactivity change going down Group 7?

Answer 10

• Reactivity will decrease!
• increasing atomic radius and increasing shielding
• This will mean more repulsion and less electrostatic attraction with outermost electrons and positive nucleus
• Less able to attract 1 electron to complete outer shell

Question 11

What are 2 main examples of Disproportionation in halogens?

Answer 11

1. Cl2 + H2O&raquo_space; HClO + HCL!!
2. Cl2 + NaOH&raquo_space; NaClO + NaCl + H2O!!

Question 12

What are the main uses of the main 2 Disproportiation reactions for Halogen?

Answer 12

• Producing both Chloric Acid and Hydrochloric Acid will act as water purification
• Bacteria are killed by ClO- ions and HCL, while ClO- ion acts as weak bleach, being alkaline!
  1. Producing Sodium Chlorate will provide a very large concentration of chlorate ions, providing ions for home bleach!
  2. Reaction MUST BE COLD, otherwise NaClO3 is produced, instead of NaClO

Question 13

Risks vs Benefits of using Cl2 for water purification?

Answer 13

1. Good = Kills bacteria, Disinfects water
2. Bad = Toxic, can react with organinc hydrocarbonds present ( Chlorinated hydrocarbons&raquo_space; cancer……)

Question 14

How can we combine Silver Nitrate test for halogens, with aqueous Ammonia?

Answer 14

1. Ag+ ion gives WHITE = Cl, CREAM = Br, YELLOW = I2
2. however! we can use aqueaous ammoniato give CLARITY and GREATER CONTRAST for halogens: Chloride = soluable at low conc Bromide = Soluable at high conc only Iodide = Completely Insoluable!

[Ag+ + X-&raquo_space; AgX(s)]

PRECIPITATES REMAIN THE SAME INITIAL COLOUR WITH Ag+ WITH ALL AMMONIA TESTS!!!