Chemistry 9-water Flashcards
Hard water generally means more what in the water
Magnesium/calcium ions
When hard water is heated, what forms
Scale (calcium carbonate)
scale is also a what? what does this generally mean for kettles
Thermal insulators
Means it becomes less efficient
What are the two types of hardness of water
Temporary
Permanent
Temporary Hardness is caused by what?
Hydrogencarbonate ion (HCO3)-
Permanent Hardness is caused by what
Dissolved calcium sulfate
How is temporary hardness removed?
What does it form
removed by heating
calcium carbonate + Carbon dioxide + water
Limescale (calcium carbonate)
why doesnt heating not work on permanent hardness?
heating a sulfate ion doesnt do anything
What can be added to both types of hardness water
What forms and why
Sodium carbonate
Added carbonates react with calcium/magnesium ions in water to form calcium/magnesium carbonates
What sort of columns remove both types of hardness?
Ion Exchange column
Columns have high density sodium ions which swap out the calcium/magnesium ions in the water
Oxygen + Hydrogen form water in what type of reaction
Exothermic Reaction
What is found in a fuel cell?
Whats formed between the two
Heat energy and water is produced from hydrogen/oxygen
Hydrogen-Oxygen fuel cells involve what type of reaction?
Redox Reaction
The electrolyte found in the fuel cell is generally what
Which part (cathode/anode) does the oxygen go into?
" hydrogen "
Potassium hydroxide
Oxygen = cathode
Hydrogen =anode
Oxygen gains what at the cathode to form what ions
What type of reaction is this
Gains electrons at the cathode
reacts with water to form OH- ions
reduction
