chemicals form the sea Flashcards
what is salt used for?
food as a preservative to give flavour
what is scattered on the roads in winter?
rock salt
what else is salt used for?
used in chemical industry to make other chemicals
how can salt be extracted? and what type of salt is it?
from rock by using underground cutting machines. The salt is impure it is called rock salt
how else can rock be extracted?
drill a borehole into the salt layer and pump water down. The salt dissolves and can be pumped back up to the surface It can then be evaporated
what is subsidence?
when the ground underneath ruptures
what is salt an important source of?
chlorine and sodium hydroxide
what derive from salt?
bleaches, PVC and solvents
when is chlorine gas produced?
when concentrated salt solution or melted salt is electrolysed
how does a simple laboratory test for chlorine include?
hold moist litmus paper in a test tube of the gas. The litmus paper turns white, chlorine is a bleach- it bleaches the colour of a indicator
what is chlorine gas used for?
to sterilise drinking water supplies, to make bleach solvents and plastics
what is hydrogen used for?
margarine
what is sodium hydroxide used to make?
soap
what is the equation for the electroyolosis of brine?
water+sodium chloride—hydrogen+chlorine+sodium hydroxide
how can concentrated sodium chloride be separated
electrolysis
where is hydrogen made?
negative cathode
where is chlorine made?
positive anode
why is it imported to use inert electrodes?
so that products don’t react before they are collected and the electrodes do not dissolve
what happens during the electryolosis of nacl solution?
na+ and h+ ions go to the negative cathode
cl- and oh- ions go to positive anode
at the cathode hydrogen is made- electrons are gained so this is reduction as shown in this half equation
write the word equation for what happens at the cathode
2h- + 2e- —- h2
where does oxidation happen?
anode
write the word equation for what happens at the anode
2c- – 2e- — cl2
what do the ions not discharged make?
sodium hydroxide solution
what is the equation for this ?
na+ + oh—– NaOh
