module 3: periodicity, g2 and g7

Question 1

uses of cl: bleach

Answer 1

ClO- kills bacteria

Question 2

bleach equation

Answer 2

cl2 + 2NaOH -> NaClO + NaCl + H2O

Question 3

uses of Cl: disinfecting drinking water

Answer 3

chloric acid and chlorate ions kill bacteria

Risk: Cl is toxic
Cl can react with hydrocarbons to form chlorinated hydrocarbons (carcinogens)

Question 4

disinfecting water equation

Answer 4

Cl2 + H2O -> HClO + HCl

Question 5

halogens are soluble in…..

Answer 5

H2O + organic solvents

Question 6

colours in water

Answer 6

cl pale green
Br yellow to orange-red
I brown

Question 7

colours in cyclohexane

Answer 7

cl green
Br red-brown
I violet

Question 8

what happens to solubility as you go down group 7?

Answer 8

decreases because

atomic radius increases
shielding increases
attraction decreases

Question 9

halogens @ room temperature

Answer 9

F pale yellow gas
cl pale green gas
Br dark red liquid
I shiny black solid

Question 10

what process does Iodine undergo??

Answer 10

sublimation
forms purple vapour

Question 11

Halide ions reacting with AgNO3

Answer 11

cl white precipitate
Br cream precipitate
I yellow precipitate

Question 12

silver halides reacting with dilute NH3

Answer 12

AgCl dissolves
AgBr does not dissolve
AgI does not dissolve

Question 13

silver halides reacting with concentrated NH3

Answer 13

AgCl dissolves
AgBr dissolves
AgI does not dissolve

Question 14

trends in groups

Answer 14

same no e- in outer shell
mp increases
ionisation energy decreases
atomic radius increases
nuclear charge increases
similar chemical and physical properties

Question 15

group 2 solubility trends hydroxides

Answer 15

slightly soluble in water, may form precipitate instead of alkaline solution

solubility increases down the group becoming more alkaline

Question 16

trends in periods

Answer 16

*highest energy e- in same shell
*atomic radius decreases (contraction)
*ionisation energy increases
*nuclear charge increases
*melting point decreases (some exceptions)
metals> giant covalent > simple molecules

Question 17

group 2 physical properties

Answer 17

reactive
low density
ductile
malleable
relatively low mp

Question 18

group 2 electron configuration

Answer 18

s-block
2 e- in outer shell
form 2+ ions

Question 19

why does solubility increase down group 2?

Answer 19

larger ions= lower lattice enthalpy of hydroxide salt

Question 20

solubility of group 2 oxides

Answer 20

react with water forming alkaline solutions
increases down group

Question 21

solubility of group 2 sulfates

Answer 21

decreases

Question 22

uses of group 2 compounds

Answer 22

ca(OH)2 used in agriculture to neutralise acidic soils

Mg(OH)2 and CaCO3 used as antacids to neutralise acids that cause indigestion

react with HCl

Question 23

Ca(OH)2 equation

Answer 23

Ca(OH)2(s) + 2H+(aq) -> Ca2+(aq) + 2H2O(l)

Question 24

conditions for bleach reaction

Answer 24

cold and dilute NaOH