Solvents and solutes Flashcards
What is a solution?
A homogenous mixture of two or more substances, with a solvent and solute mixing to usually be in the same liquid phase as the original solvent
The solute can be solids, liquids or gases
What is a mixture of gases called?
A mixture
What is the difference between solutions and mixtures such as colloids?
Solutions are homogenous whereas colloids etc. are non-homogenous
What properties do the hydrogen bonds in water give it compared to other fluids?
Excellent solvent as polar
Higher melting/boiling point
Higher heat of vaporisation
Higher surface tension
Molecules expand on freezing (only on-metallic substance that does this)
Solid is less dense than the liquid
What kind of binding is seen in water molecules?
Covalent bonds between oxygen and hydrogen form through shared pairs of electrons
What is the molecular structure of water?
Polar and non-linear (bent). Negative O and positive H
What type of bonds form between different molecules?
Hydrogen bonds between very negative O and positive H’s on other molecules (dipole dipole interaction)
How many hydrogen bonds can each water molecule form?
4
Two Hs attract to O
One O attracts to each H
What temperature is ice most dense at?
4 degrees c
What types of molecules are hydrophilic?
Polar or ionic
What molecules are hydrophobic?
Non polar e.g. benzene
When water mixes with salts, what structures are formed?
Hydration shells - different shapes for negative and positively charged salts (circles and stars)
What are complex hydration shells that may form around larger non-polar solute?
Clathrate formations (forms a cage around it)
What is solubility?
The ability of a substance to dissolve in a solute
What factors effects solubility?
Pressure
Temperature
Nature of the solvent
Nature of the solute
How does pressure effect has solubility?
Higher pressure = more soluble (Henry’s law)
What happens to dissolved gas when we open a bottle of fizzy juice?
Pressure drops and gas becomes less soluble, causing bubbles (effervescence)
How does temperature alter the solubility of solids?
Makes them more soluble except temperature independent ones like NaCl
What does increasing temperature do to gas solubility?
Examples
Decreases it
Needing a bubble chamber with fluid warmers
Fizzy juice having less fizz when warm
What do non- polar substances dissolve well in?
Non polar solvents like benzene
How do we quantify solubility?
The maximum amount of suite than can dissolve in a volume of solvent under a certain temp and pressure. But as this varies with temperature, is is better to quantify with mass in mass e.g. mg/ml
What does 1% lidocaine mean?
1g in 100g or 1g in 100ml
What is a mixture?
2 substances that disperse with each other but stay in their original identify e.g. flour and water. They don’t combine chemically to make a new structure so are non-homogenous
What are suspensions?
Mixture that eventually separate e.g. mud and water. Mud will settle.
