C1 - Atomic Stucture & The Periodic Table Flashcards
(14 cards)
How can we use paper chromatography to seperate substances in a mixture.
First we need a blank white peice of chromatography paper with a horizontal line drawn near from the bottom around 2cm up. We then place are spot(s) of ink onto the line using a ruler and pencil as its insoluble so won’t dissolve in the solvent.
We then fill up a shallow amount of solvent/water inside a beaker and place the paper inside the beaker ensuring the line dosnet become submerged.
(We can place a lid ontop of container for extra safety) As the solvent seeps up the paper it will then carry up the ink with it leaving a spot in a different place- one spot per dye in the ink l.
When the solvent has nearly reached the top of the paper we take it and leave it to dry, what we have left is are chromatogram.
How do we work out the rf value
Rf Value = Distance travelled by solvent ÷ Distance travelled by ink
In chromatography what is tye stationary phase and what is the mobile phase
Stationary phase- Paper
Mobile phase- Solvent
During paper chromatography,
Chemicals that are More soluble in the solvent spend _____ time in the Mobile Phase therefore move faster. However chemicals that are Less soluble are more attracted to the paper spending more time in the stationary phase and therefore moving more ______.
MORE
SLOWLY
What happens when we do paper chromatography with a pure substance
It only produces one spot as the ink is made up of once substance/chemical
When can we use filtration.
How is it carried out
Filtration is used when seperating an insoluble solid from a liquid. We firstly use a conical flask with a filter funnel at the top lined with filter paper comtaining little pores, we then pour our solution down the flash, our solids/solute will get stuck at the filter paper and our solvent will pass through
How is evaporating used to seperate an insuble solid from a solution
For evaporation we place our solution inside an evaporating dish, ontop of a tripod which we slowly heat with a bunsen burner, this will cause the solvent to start evaporating and the remaining solution to get more concentrated, after a while crystals will start to form and all the solvent would of evaporated leaving us with dry crystals from our solid.
Advantage and disadvantage of evaporation
Advantage - Relatively Quick and easy way to seperate solid from a solution
Disadvantage - Some solids decompose when there heated which is called thermal decomposition so we’d end up breaking our solid down into something else
For soluble solids in solution that are susceptible to heat what method do we have to use to seperate them
- How is it carried out
Heat our solution very gently in a evaporation dish using a water bath, once some of the solvent has evaporated and we start to see crystals forming in the solution we stop heating it and leave it to cool more as the solution cools more crystals will start the form as solids are less soluble at cooler temperatures, next we filter out any possible excess solvent using a filter paper and funnel and then drying the crystals by leaving them somewhere warm or drying them up in a oven
We can use simple distillation to seperate out a liquid from a solution e.g. Pure water from sea water.
How do we set up the parameters of distillation.
First we have a flask that contains the solution were trying to seperate which is sealed at the top with a bung so no evapprated gas can escape. Through the bung we have a hole only for the thermometer so we can measure the temperature inside the flask, we have a bunsen burner placed under the flask. We then have a condensor attached to the flask that consists of a main pipe surrounded by a water jacket that contains a stream of continously cold flowing water with the water being fed into the water jacket at the bottom and coming out at the top, beneath the end of our condenser well have some sort of beaker to catch our pure liquid.
When all parameters are set up. How can we use simple distillation to seperate a liquid for our solution
Our first step is to heat up the mixture so that the liquid which we want evaporates, as we rise it to the top of the flask, the pressure will force it down to the condensor and because were pumping cold water through the water jacket the vapour will cool and condense into liquid form to run down the pipe and be collected inside the beaker.
E.g. as we heat the sea water we’ll get more and more pure and distilled water till all we have left in the flask is salt
What do we use for seperating several liquids of a mixture
Fractional distillation
2 features of fractionation rod in fractional distillation
It is full of little grass rods that provide a high surface area, the column is cooler at the top then the bottom so if an unintended solution evaporates it will condense back down as the rod will be much cooler than its boiling point
How do we carry out fractional distillation
1st heat our mixture to the boiling point of the lowest one in our solution, this would cause that liquid to evaporate and rise up the fractionating column to then pass into the condensor back into liquid and caught into the beaker.
By chance any of the other liquids may also rise but as they come into contact with all of the glass rods that are much cooler than there boiling points, it would condense back I to liquid form and condense back down into the flask.
Next do the same thing all over again for the next liquid and raise the temperature for the mext boiling point and use a different flask
