Salts Flashcards
What are salts?
Ionic compounds
Salinity
when ionic salts dissolve in water, dissociate to produce moving charged ion. Conduct electricity to a certain extent depending on how many ions present
Relationship between concentration and conductivity
- linear
- higher the concentration the greater the conductivity
Electrical conductivity testing
- battery
- two electrodes
- a light globe
- ammeter
- the flow of ions present in solution completes circuit and powers globe
Conductivity measured by
brightness of the globe
- ammeter to measure current
Hygroscopic
- absorb water from air and contain water molecules in chemical formula
- hydrated salts
Anhydrous form
absense of water
Gravimetric analysis
- determine concentration of salt in the water using a precipitation reaction
Steps to a gravimetric analysis
- Prepare analyte solution (filter out insoluble materials)
- Add excess of precipitating agent to ensure all ions being analyzed end up in the precipitate
- Separate and collect precipitate using filtration
- must be washed with distilled water to removed impurities - Dry sample to ensure all water is removed multiple times until mass is constant
- Weigh precipitate using accurate balance and calculate analyte mass
Insoluble materials not filtered before forming the precipitate
Overestimation - the apparent mass of the precipitate will increase
Incomplete precipitation as not enough precipitating agent is added
Underestimation - less precipitate than expected
More than one precipitate forms
Overestimation - more precipitate than expected
Forming a precipitate that is too soluble
Underestimation - not all ions being analysed will be in the precipitate
Small amounts of precipitate lost during transfer
Less precipitate than expected
Incomplete rinsing of precipitate
Overestimation - precipitate contains absorbed ions which increases the mass
