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$Na_2CO_{3(aq)}+ 2HCl_{(aq)} \rightarrow 2NaCl_{(aq)} + CO_{2(g)} + H_2O_{(l)} \ \checkmark$
Observation: Colourless solution is added to a colourless solution, a colourless, odorless gas is produced and released through bubbles (Effervescence) from the colourless solutions.
$Ba(NO_3){2(aq)} + H_2SO{4(aq)} \rightarrow BaSO_{4(s)} + 2HNO_{3(aq)} \ \checkmark$
- all acids are stable, more or less, unless its carbonic acid
- there are only few reactions with some metals when you have oxides formed.
examples of chemical change include PH change
e.g. NaOH + HCl → NaCl + H2O
both sides are colourless solutions (so no physical changes), how do we know that there was a chemical reaction? Change in PH levels - using PH meter
or indicators
How do we separate things?
Physical Means:
- Filtration (Gravity filtration)
- used to separate heterogeneous mixtures composed of solids and liquids
- Uses a porous barrier to separate the solid from the liquid
- Smaller particles of liquid passes through leaving the solid in the filter paper.
- Need to be able to draw a diagram
- Chromatography
- Centrifuging - separate plasma from blood
- Evaporating - similar to distillation, you evaporate solvent completely until dryness
- Evaporation can be used to separate a solute from the solvent in a solution.
- evaporating basin
- Crystallization - if solution is not thermally stable
- Separation technique that results in the formation of pure solid particles from a solution containing the dissolved substance
- As one substance evaporates, the dissolved substance comes out of solution and collects as crystals
- Produces highly pure solids
- Rocky candy is an example of this
- Advantage: you will always form a pure substance, not always the case with evaporation.
- Dissolving
- Decantation
- Decanting is done to separate particulates from a liquid by allowing the solids to settle to the bottom of the mixture and pouring off the particle-free part of the liquid. Another method is to allow two immiscible liquids to separate and the lighter liquid is poured off.
- Sieving
- a porous material is used to separate particles of different sizes.
- method is most commonly used to effect gross separations, as of liquids from suspended crystals or other solids
- to accelerate filtration, pressure usually is applied
- a series of sieves is attached, with the screen of largest hole size at the top.
- Flotation
- Distillation
- used to separate homogenous mixtures
- based on difference in boiling points of substances involved
- Be able to draw a distillation apparatus
Slightly soluble = soluble
- NaCl and CuCl_2 are both soluble in water, so using water to dissolve one but not the other doesn’t work. However, in Ethanol, as NaCl has a strong ionic bond, ethanol isn’t polar enough (dipole). So NaCl will not dissolve and CuCl_2 will.
Solutions:
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Solution: A mixture in which the solute particles are homogenously distributed throughout particles of solvent
- Can be solid (e.g. Bronze(Metal alloys)), liquid (e.g. Sea water) or gas (e.g. Air)
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Aqueous Solution: Liquid solution where the solvent is water
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Solvent: The major component of a solution by mass
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Solute: The minor components of a solution by mass
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Dissolving: Solid particles are separated and distributed throughout the mixture, increasing solution concentration.
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Unsaturated: Contains less solute than the solvent is normally able to dissolve
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Saturated: Contain the same amount of solute that the solvent is normally able to dissolve
- Rate of dissolving and crystallization are equal
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Supersaturated: Contains more solute than the solvent is normally able to dissolve
- Can be achieved through heating and dissolving, then carefully cooling the solution.
Solubility curves.
Solubility is measured in how many grams of solute dissolves in 100 mL.
