Water solutes + safety Flashcards
What is hard water?
Water that has dissolved magnesium or calcium ions
What happens when hard water is mixed with soap?
Scum forms and not lather due to calcium + magnesium ions reacting with the soap and forming a precipitate (scum)
Why do we consider hard water as a disadvantage?
It causes soap to be wasted due to scum forming and hence money
What is in a solution?
The solute- substance being dissolved
Solvent: substance dissolving the solute (e.g. in sodium chloride solution, solute=sodium chloride and solvent=water)
What causes temporary hardness?
Dissolved calcium hydrogencarbonate
What does softening mean?
Removing hardness from water. Boil the water which breaks down the calcium hydrogencarbonate. Unsoluble calcium carbonate forms so its calcium ions cant react with soap to form scum.
What causes permanent hardness?
Substances such as calcium sulphate
Difference tween permanent and temporary hardness?
Unlike temporary, permanent hardness cannot be removed by boiling water
Why would boiling not remove all of the hardness?
Water can contain both types of hardness
How does an ion exchange column soften water containing permanent hardness?
Hard water enters column and is swapped for sodium ions from the resin. Sodium ions dont form scum so water coming out is softened
Describe the steps needed to make a soluble salt from an insoluble base
- Add excess of insoluble base to solvent until you ensured all the acid has reacted.
- Filter insoluble base so excess is removed and so the salt solution can pass through as filtrate
- Evaporate to produce crystals of the salt
What reaction takes place during neutralisation?
Hydrogen ions from the acid and hydroxide ions from the base react to produce water
Explain the process of titration
Transfer alkali to conical flask using pipette and add drops of phenolphthalein indicator. Fill burette with acid and record reading. Add acid to alkali when tap openand swirl content. Colour should start to change from pink to colourless. Near end, alkali drop by drop. Note new reading when tap closed. Repeat til concordant results
What does concordant mean?
Results that are identical or close to each other
