1 Experimental and Separation Technique Flashcards
Separates: liquid-liquid mixtures
Purity: impure
How it works: Involves heating a solution to evaporate the solvent, leaving behind the solute as a dry solid residue. The purity of the resulting solid depends on the initial composition of the solution and the potential for contaminants to remain in the residue.
evaporation to dryness
problems with evaporation to dryness
Impurities Present in Solid Residue: Evaporation to dryness may not effectively separate pure substances from impurities since any soluble impurities will remain in the solid residue along with the desired substance, resulting in impure products.
Solute Decomposition: Additionally, evaporation to dryness is not suitable for all solutes, as some solutes may undergo decomposition upon heating. For instance, compounds like sugar can decompose to produce water and carbon, while hydrated copper(II) sulfate crystals can decompose to form anhydrous copper(III) sulfate powder. This decomposition can lead to the formation of undesired products and hinder the separation process.
soluibility measurement
how many grams of a given substance will dissolve in a given volume of solution.
eg. the solubility of sucrose at 80C is 350g/100g. (350g of sucrose can be dissolved in 100g)
solute vs solvent
solute is the substance being dissolved
solvent is the dissolving medium
Separates: Solid-liquid mixtures.
Purity: impure
How it works: Filtration works by passing a mixture through a porous material (such as filter paper or a filter membrane) that allows the liquid component (the filtrate) to pass through while trapping the solid component (the residue). The solid residue collected on the filter is typically purer than the original mixture, as the liquid component carries away dissolved impurities.
filtration
whats the solid collected via filtration called and the solution passing through the filter paper called
residue and filtrate
Separates: Immiscible liquid-liquid mixtures. according to the difference in density
Purity: impure
How it works:
▪ Pour the mixture into a separating funnel
▪ Allow the two liquids to separate into two layers
▪ The liquid with a lower density(oil) will form the
upper layer
▪ The liquid with a higher density(water) will form
the lower layer
▪ Open the tap to run out the water into a beaker
▪ Use another beaker to collect the oil
separating funnel
pour the mixture into a separating funnel
allow the 2 liquids to separate into 2 layers.
the liquid with a lower density will form the lower layer
open the tap to run out the water into a beaker
use another beaker to collect the oil
liquid - liquid (pure)
chromatography
boiling stone
to ensure smoother boiling
how do you check purity in a solution
check if it melts or boils at a fixed temperature. (eg. if water has impurities it may boil at a higher temperature like 130)
run it thru a chromatography test. if only one spot appears it is pure
Separates: miscible Liquid-liquid
Purity: pure
How it works:
▪Mixture is heated
▪ Liquid in mixture boils and turns to vapour
▪ This pure vapour rises and enters the condenser
▪ In the condenser, this vapour is cooled (condensed) to its liquid state. This liquid, called the distillate, is collected
distillation
Separates: miscible Liquid-liquid mixtures
Purity: pure
How it works:
▪Mixture is heated
▪ Liquid in mixture boils and turns to vapour
▪Liquid with the lowest boiling point boils first.
▪it has no where to condense cuz every surface is at his boiling point and can only go into the condenser
▪
▪ This pure vapour rises and enters the condenser
▪ In the condenser, this vapour is cooled (condensed) to its liquid state. This liquid, called the distillate, is collected
fractional distillation
different liquids have different boiling points and will condense at different points of the fractionating column
how to find the boiling point of a substance
When the temperature reading stops rising and remains constant as heating continues.
Fractionating column purpose
provides larger surface area for effective separation of the mixture of vapours through repeated condensation and boiling and the presence of a temperature gradient.
what salts is always soluble
all nitrates are always soluble
group 1 metals
ammonium
accetates
how to identify wheter u get solid gas aqueous products from an equation
eg. reaction between lead(II) nitrate and hydrochloric acid
sec 2 equation stuff
solid - solid - 1
solid - liquid - 1
liquid - liquid - 5
ss - sublimation
sl - filtration
ll - distillation, crystallisation, evaporation to dryness, separating funnel, paper chromatography
DECCaF
which direction does water go in a condenser
water goes upwards so that there are no gaps with gas bubbles
y does the thermometer need to be at the top of the fractionating column,
for the vapour of the lower boiling point to reach the thermometer to indicate that it has started boiling
how to separate pure methane from gases
use fractional distillation on liquified air
what does sublimation separate and y isit special
its separates a mixture of solids
and its the only that does other than magnetic which is bad
does sublimation result in pure results
only the sublimed solid is pure, the rest left behind isnt.
but its the only solid - solid separation tech so go figure
experimental steps for sublimation
Heat the solid mixture with an inverted filter funnel placed above the evaporating dish. A white sublimate (ammonium chloride) will be collected on the inverted filter funnel
how does sublimation work in theory
Converts a solid directly into vapor without passing through the liquid phase, leaving behind impurities that do not sublime.
what does crystallisation separate and y isit special
separates liquid-liquid mixtures
it results in pure results
does sublimation result in pure results
yes, the results r pure
how does crystallisation work
When the solution is heated, most of the solvent is evaporated off. The hot solution is then allowed to cool. The solution is now said to be saturated. As the solution cools, the solubility of the solute decreases. This means that the mass of solute that can dissolve in the solution is decreased. The solution cannot hold any more solute and thus the dissolved solute appears as pure crystals. The impurities remain dissolved in the solution.
BASICALLY, jar of solution w a white ppt(solid), heat it and the solute solubility increases so it dissolves. NO MORE PPT. when u cool it slowly the solid becomes less soluble, so the excess solute crystalises out
what can sublime that might come out
ammonium chloride, iodine, carbon dioxide
