Group 7 (old set tests in one flashcard)

does melting point increase or decrease going down the group, why?

increases because there are more electrons in the van der waals, making them stronger

why does oxidising power decrease going down?

more electron shells, more shielding that repels the electron that is gained

why does reactivity decrease going down?

gaining an electron is harder because the positive nucleus is further away weakening its attraction of an electron, further weakened by shielding

why does reducing power increase going down?

halide ions become larger, weaker electrostatic attraction between nucleus and outer electrons so is easier to overcome

chloride

• colour & state

• acid

• AgNO3

• dilute NH3

• concentrated NH3

• observation with H2SO4

• pale green gas

• no change

• white precipitate of AgCl

• dissolves

• dissolves

• white steamy fumes HCl

bromide

• colour & state

• acid

• AgNO3

• dilute NH3

• concentrated NH3

• observation with H2SO4

• orangey brown liquid

• no change

• cream precipitate of AgBr

• doesn’t dissolve

• dissolves

• steamy HBr fumes/SO2 smell

iodide

• colour and state

• acid

• AgNO3

• dilute NH3

• concentrated NH3

• observation with H2SO4

• grey-black solid, purple when sublimes

• no change

• yellow precipitate of AgI

• doesn’t dissolve

• no change

• steamy HI fumes and H2S smell

carbonate

• HCl

• AgNO3

• effervescence

• no change if acid already reacted/white precipitate if not enough acid added

hydroxide

1cm3 solution, red litmus paper —> blue

SO4 ions

dilute HCl + BaCl2 —> white precipitate of BaSO4

ammonium ions

Add NaOH and dip red litmus paper → blue

why is nitric acid added?

to remove any anions that could interfere

why isn’t HCl used?

because it would form a white precipitate