chemicals form the sea

Question 1

what is salt used for?

Answer 1

food as a preservative to give flavour

Question 2

what is scattered on the roads in winter?

Answer 2

rock salt

Question 3

what else is salt used for?

Answer 3

used in chemical industry to make other chemicals

Question 4

how can salt be extracted? and what type of salt is it?

Answer 4

from rock by using underground cutting machines. The salt is impure it is called rock salt

Question 5

how else can rock be extracted?

Answer 5

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

Question 6

what is subsidence?

Answer 6

when the ground underneath ruptures

Question 7

what is salt an important source of?

Answer 7

chlorine and sodium hydroxide

Question 8

what derive from salt?

Answer 8

bleaches, PVC and solvents

Question 9

when is chlorine gas produced?

Answer 9

when concentrated salt solution or melted salt is electrolysed

Question 10

how does a simple laboratory test for chlorine include?

Answer 10

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

Question 11

what is chlorine gas used for?

Answer 11

to sterilise drinking water supplies, to make bleach solvents and plastics

Question 12

what is hydrogen used for?

Answer 12

margarine

Question 13

what is sodium hydroxide used to make?

Answer 13

soap

Question 14

what is the equation for the electroyolosis of brine?

Answer 14

water+sodium chloride—hydrogen+chlorine+sodium hydroxide

Question 15

how can concentrated sodium chloride be separated

Answer 15

electrolysis

Question 16

where is hydrogen made?

Answer 16

negative cathode

Question 17

where is chlorine made?

Answer 17

positive anode

Question 18

why is it imported to use inert electrodes?

Answer 18

so that products don’t react before they are collected and the electrodes do not dissolve

Question 19

what happens during the electryolosis of nacl solution?

Answer 19

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

Question 20

write the word equation for what happens at the cathode

Answer 20

2h- + 2e- —- h2

Question 21

where does oxidation happen?

Answer 21

anode

Question 22

write the word equation for what happens at the anode

Answer 22

2c- – 2e- — cl2

Question 23

what do the ions not discharged make?

Answer 23

sodium hydroxide solution

Question 24

what is the equation for this ?

Answer 24

na+ + oh—– NaOh