water chemistry

Question 1

water cycle

Answer 1

describes all the changes that water undergoes as it moves through the earth

Question 2

hard water

Answer 2

water that will not easily form a lather with soap

Question 3

what are the two ions that cause hard water

Answer 3

ca+2 mg+2

Question 4

when hard water forms scum with soap

Answer 4

Ca+2 + 2 C17H35COO- —> (C17H35COO)Ca

Question 5

how does hard water form

Answer 5

H2O + CO2 —> H2CO3

H2CO3 + CaCO3 —> Ca(HCO3)2

Question 6

temporary hardness

Answer 6

hardness that can be removed by boiling

Question 7

permanent hardness

Answer 7

hardness that cannot be removed by boiling

Question 8

distillation

Answer 8

involves boiling and condensing vapour and all liquids solids and gases are removed resulting in the purest form of water.

Question 9

adding washing soda

Answer 9

crystals of hydrated sodium carbonate to water and Ca+2 in water and Na+ in crystals swap
Ca+2 removed by ppt but Na+ remains in water
wastes less soap but only for small volumes

Question 10

ion exchange resins

Answer 10

synthetic materials that exchange or swap ions that cause hardness for ions that do not

Question 11

soft household water

Answer 11

cation ion exchange resin
swaps all the Ca2+ ions for Na+

Question 12

complexometric titration

Answer 12

a titration involving the formation of a complex between metal ions and a reagent such as EDTA. The end point is detected by a sharp decrease in the concentration of free metal ions

Question 13

what is the colour change of the edta titration

Answer 13

wine red to blue