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Solvent, Solute, Solutions and Solubility. Solutions. All solutions consist of 2 parts Solvent (the substance that does the dissolving, makes up the majority of the solution – usually liquid, but can also be solid or gas) - PowerPoint PPT Presentation
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Solvent, Solute, Solutions and Solubility
Solutions• All solutions consist of 2 parts– Solvent (the substance that does the dissolving,
makes up the majority of the solution – usually liquid, but can also be solid or gas)
– Solute (the substance that dissolves – can be solid, liquid or gas)
Solution
Solvent
Solute
A solution is formed when a solute dissolves in a solvent
State at RTP
Solid Liquid Gas
Solvent Iron Water Nitrogen
Solute Chromium Sugar Oxygen, carbon dioxide and other gases
Solution Stainless steel(Metal alloy)
Sugar syrup Air
Liquid solutions at rtp – Solvent = Water?
• Usually, we use water as a solvent because many substances can dissolve readily in it.
• However, the solvent does not have to be water!
• Substances that do not dissolve in water may be soluble in other solvents
• E.g. ethanol (an alcohol), oil..
We shall focus mainly on aqueous solutions
• Chlorine– Greenish-yellow gas– Low melting and
boiling point– Poor electrical
conductor
Chlorine is used in bleaches for our clothes.
Solvent :
Solute :
Water
Chlorine gas
7Uses: antiseptic
Iodine is a non-metallic element that sublimes when heated to form a violet vapour.
When dissolved in ethanol, it forms tincture of iodine, used as an antiseptic.
Solvent :
Solute :
Ethanol
Iodine
Is a solution a..
• Element?• Compound?• Mixture?
Mixture!No fixed proportion of
solute / solvent required
Solubility• The solubility of a substance in a
solvent is the maximum quantity of that substance which can dissolve in 100 g of the solvent at a given temperature
• (units: g / 100 g)
• Copper(II) sulfate has a solubility of 32 g /100 g in water (at 20°C)
Describing solutions
• Copper(II) sulfate has a solubility of 32 g /100 g of solvent (at 20°C)
• 100 g of water (100 ml)– 2 g of copper(II) sulfate
– 30 g of copper(II) sulfate
– 32 g of copper(II) sulfate
– 35 g of copper(II) sulfate
Dilute solution
Concentrated solution
Saturated solution
Suspension
Factors affecting solubility?• Type of solute – e.g. copper(II) sulfate / salt
/ sugar• Type of solvent– e.g. water / ethanol
• Temperature of solvent– Generally, solubility as
temperature • Pressure of surroundings– Generally, solubility as
pressure
Suspension?
The amount of substance present is over its solubility limit
35 g 100 g
Copper(II) sulfate has a solubility of 32 g /100 g of solvent (at 20°C)
Suspension?
The substance does not dissolve in the solvent
Solutions Suspensions
What happens when it is passed through filter paper?
No visible changeSolid particles are trapped on filter paper
What happens when it is left to settle?
No visible changeSolid particles settle on the bottom of the beaker
Is it homogenous (same throughout)? Yes No
Can light pass through?
Yes – solutions are ALWAYS CLEAR!
No – a suspension is ALWAYS CLOUDY.
Common errors..
• Clear solution?• Transparent solution?• Colourless solution!
• Cloudy solution?• White colour solution?• Milky solution?• Suspension! (White precipitate in a colourless solution)
X
XX X
X
Rate of dissolving
Rate of dissolving is NOT solubility!
• Recall:
• Rate of dissolving: How fast it dissolves
• The solubility of a substance in a solvent is the maximum quantity of that substance which can dissolve in 100 g of the solvent at a given temperature
Making solutions quickly
• Factors affecting rate of dissolving– Temperature of solvent– Particle size of solute– Stirring
• Assumption: The amount of solute used is << solubility limit