A3 - group 2,7 qualitative analysis

Question 1

what is the trend in reactivity of group 2

Answer 1

atomic radius increases
shielding increases
nuclear attraction decreases
easier to remove to outer shell electrons

Question 2

what is the trend in melting points down group 2

Answer 2

melting point decreases
ionic radius increases
charge density decreases
electrostatic attraction between ions and delocalised electrons decrease strength of metallic bonds

Question 3

the trend in first ionisation energy down group 2

Answer 3

atomic radius increases
attraction between nucleus and valence electrons decreases
first ionisation energy decreases

Question 4

what are the observations group 2 metals reacting with water

Answer 4

bubbles
increasingly vigorous bubbling

Question 5

why is the 2nd ionisation energy larger than the 1st ionisation energy

Answer 5

larger because its removing the electron from an ion rather than then an atom
ions have a larger attraction between the electrons and nucleus
more energy needed

Question 6

what is the use of Magnesium hydroxide

Answer 6

treat excess stomach acid
milk of magnesia
neutralise mouth acids in toothpaste

Question 7

what is the use of calcium hydroxide

Answer 7

add to fields to make fields more alakaline
test for carbon dioxide

Question 8

what is the use of calcium carbonate

Answer 8

treat excess stomach acid

Question 9

what is the use Barium chloride

Answer 9

test for sulphate ions

Question 10

what is the order for testing an unknown substance

Answer 10

CASH
carbonates
sulfates
halides

Question 11

what is the test for ammonium

Answer 11

add sodium hydroxide
warm the solution
place red litmus paper near tube
litmus will blue

Question 12

test for carbonate ions

Answer 12

add nitric acid
if carbonate ions are present bubbling will occur

Question 13

test for sulphate ions

Answer 13

add nitric acid
add barium chloride aq
white ppt forms

Question 14

test for halide ions

Answer 14

add nitric acid
add silver nitrate
Cl - white ppt
Br - cream ppt
I - yellow ppt

Question 15

what block are halogens in

Answer 15

p block

Question 16

what type of molecules are halogens

Answer 16

diatomic

Question 17

describe the trend of boiling points down group 7

Answer 17

• down the group the group 7 molecules increase the number of electrons
• stronger london forces between molecules
• more energy is required to break them

Question 18

describe why electronegativity decreases down the group

Answer 18

• number of protons increases down the group
• shielding increases
• atomic radius increases
• attraction between the nucleus and shared pair of electrons is weaker

Question 19

why are halogens good oxidising agents

Answer 19

ability to donate its electrons to other species

Question 20

what is the equation between water and chlorine

Answer 20

Cl2 + h20 —> HClO + HCl

Question 21

what are the advantages of sterilising water with chlorine

Answer 21

prevents waterborne diseases
kills bacteria

Question 22

disadvantages of sterilising water with chlorine

Answer 22

chlorine is toxic
can react to hydrocarbons to produce carcinogenic chlorinates hydrocarbons

Question 23

what is the equation to produce bleach
NaOH with Cl2

Answer 23

2NaOH + Cl2 —-> NaCl + NaClO+ H2O