C3.3: Water Flashcards
How does a titration result show the purity of a substance?
Can calculate the amount of synthesised chemical in the sample to find the original substance’s purity
How would you measure the hardness of water?
Titration with soap solution
2 advantages and 2 disadvantages of hard water
+ Reduces heart disease. + Development/maintenance of healthy bones and teeth
- £££ More soap needed. - Temp hard water makes scale which reduces efficiency of heating systems/kettles
What are the two types of hard water and how are they identified?
Temporary- can be softened by boiling, contains hydrogencarbonate ions (HCO3-) which react with Ca and Mg ions to form precipitates
Permanent- remains hard when boiled and contains sulfates
What happens when you add sodium carbonate to hard water?
It reacts with the Ca and Mg ions to form a precipitate of CaCO3 and MgCO3
Name two ways of softening water
- Adding sodium carbonate (washing soda)
- Ion exchange (commercial water softeners)
How does an ion exchange column or commercial water softener soften water?
It contains H+ ions or Na+ ions which replace the Ca or Mg ions when hard water passes through the column
For water to be of a high enough quality for humans to consume it should have low levels of what? (2 things)
Dissolved salts and microbes
Water of the correct quality is produced by:
3 things
Choosing an appropriate source
Passing the water through filter beds to remove solids
Sterilising with chlorine
Why would chlorine and fluorine be added? (One reason for each)
Cl=to reduce microbes
F=to improve dental health
Tap water filters remove dissolved substances and improve taste. What 3 substances improve taste?
Carbon or charcoal, ion exchange resins and silver which prevents bacteria growth
What are the 5 steps of a water filter system?
1) Coarse filter(metal bars) to separate large objects
2) Sedimentation tank where the sand and soil settle out
3) Al2(SO4)3 (Aluminium sulfate) and lime added to clump tiny particles to make larger ones. Sinks to bottom.
4) Fine filter (fine sand or carbon granules)=clean and sparkly
5) Small amount of chlorine added
What are the problems linked with fluoride being added to water?
- Unethical, forces people to consume fluorine when they drink tap water, takes away personal choice.
- Has been linked to bone disease+tooth mottling (staining)
How can you produce pure water and what is a drawback of this method?
- Distillation
- Lots of energy needed=high costs
What types of substance dissolve in water?
Most ionic compounds, most gases, some molecular substances
