Flashcards in C3.2 Water Deck (14):
How is hard water produced from rain water?
calcium/magnesium ions dissolve
from rocks (limestone)
What is formed when hard water reacts with soap
State one health benefit of drinking hard water
-helps maintain bones
-helps maintain teeth
-helps reduce heart disease
Why is distillation generally not used to purify water
High cost of energy
Why is chlorine added to water
What in water filters reduce the hardness of water
Ion exchange column
Suggest why water filters contain particles of nanosilver
Describe the main two steps used to treat water from reservoirs
-to remove solids
-to kill bacteria/sterilise it
A student boils some hard spring water in a pan.
The inside of the pan becomes coated with a white solid.
Explain how the white solid is produced.
-water contains calcium hydrogen carbonate (HCO3-)
-to form calcium carbonate (or limescale)
Explain how an ion exchange column softens water
-Sodium ions (Na+) in the resin
-calcium ions(Ca2+)/magnesium ions (Mg2+)
Why do some companies add fluoride to the drinking water?
-Improve dental health (reduce tooth decay)
Describe how sodium carbonate is used to soften water
-sodium carbonate is added to hard water
-calcium ions precipitate out (form a solid)
-as calcium carbonate
-which can be filtered out of the water
How is scale formed?
-temporary soft water is heated
-hydrogen carbonate ions decompose
-to form carbonates