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Physics > Solvents and solutes > Flashcards

Solvents and solutes Flashcards

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1
Q

What is a solution?

A

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

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2
Q

What is a mixture of gases called?

A

A mixture

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3
Q

What is the difference between solutions and mixtures such as colloids?

A

Solutions are homogenous whereas colloids etc. are non-homogenous

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4
Q

What properties do the hydrogen bonds in water give it compared to other fluids?

A

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

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5
Q

What kind of binding is seen in water molecules?

A

Covalent bonds between oxygen and hydrogen form through shared pairs of electrons

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6
Q

What is the molecular structure of water?

A

Polar and non-linear (bent). Negative O and positive H

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7
Q

What type of bonds form between different molecules?

A

Hydrogen bonds between very negative O and positive H’s on other molecules (dipole dipole interaction)

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8
Q

How many hydrogen bonds can each water molecule form?

A

4

Two Hs attract to O

One O attracts to each H

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9
Q

What temperature is ice most dense at?

A

4 degrees c

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10
Q

What types of molecules are hydrophilic?

A

Polar or ionic

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11
Q

What molecules are hydrophobic?

A

Non polar e.g. benzene

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12
Q

When water mixes with salts, what structures are formed?

A

Hydration shells - different shapes for negative and positively charged salts (circles and stars)

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13
Q

What are complex hydration shells that may form around larger non-polar solute?

A

Clathrate formations (forms a cage around it)

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14
Q

What is solubility?

A

The ability of a substance to dissolve in a solute

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15
Q

What factors effects solubility?

A

Pressure
Temperature
Nature of the solvent
Nature of the solute

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16
Q

How does pressure effect has solubility?

A

Higher pressure = more soluble (Henry’s law)

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17
Q

What happens to dissolved gas when we open a bottle of fizzy juice?

A

Pressure drops and gas becomes less soluble, causing bubbles (effervescence)

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18
Q

How does temperature alter the solubility of solids?

A

Makes them more soluble except temperature independent ones like NaCl

19
Q

What does increasing temperature do to gas solubility?

Examples

A

Decreases it

Needing a bubble chamber with fluid warmers
Fizzy juice having less fizz when warm

20
Q

What do non- polar substances dissolve well in?

A

Non polar solvents like benzene

21
Q

How do we quantify solubility?

A

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

22
Q

What does 1% lidocaine mean?

A

1g in 100g or 1g in 100ml

23
Q

What is a mixture?

A

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

24
Q

What are suspensions?

A

Mixture that eventually separate e.g. mud and water. Mud will settle.

25
Q

What are colloids?

A

Type of mixture where a substance is dispersed evenly though each other, with an; internal phase (dispersed substance of small 1-100nm particles) and an external phase (in which internal phase is dispersed)

Do not settle under gravity

26
Q

What are liquid in liquid colloids?

A

Emulsions

27
Q

What is an emulsion?

A

Mixture of two or more immiscible (non-homogenous) liquids that combined with input of energy but tend to settle e.g. oil and water.

28
Q

What can we use to prevent reversion of emulsions and how do these work?

A

Emulsifiers including surfactants like soya or egg. These bind electrostatically to internal phase to help maintain its position relative to the external phase, through electrostatic forces.

29
Q

What emulsifiers are used in propofol?

A

Soya lecithin and egg

30
Q

Why are surfactants called such?

A

They are surface acting molecules

31
Q

What are three different types of colloid suspensions?

A

Gelatin
Dextran
Starch

32
Q

How are gelatin colloids made?

How long do they last?

Positives and negatives?

A

Formed from hydrolysed collagens in animal tissues of 30000 Da

Last 2-4h in the circulation

Cheap but risk of anaphylaxis

33
Q

How are dextran colloids made?

Positives and negatives?

A

Polymerisation of glucose with weight of 70000 Da

Reduce viscosity of plasma

34
Q

How are starch colloids made?

How long do they last?

Positives and negatives?

A

From amylopectins linked to hydroxyethyl groups of different molecular weight, up to 200000 Da

Last up to 24h

Expensive, risk of coagulopathy and pruritus

Less anaphylaxis

35
Q

What are colligative properties?

A

Ones that vary with the number of dissolved particles rather than the identity of the solute

36
Q

What are the colligative properties of salt dissolved in water?

A

Fall in vapour pressure
Elevation of boiling point
Depression of freezing point
Changes in osmotic pressure

37
Q

What is Raoults law?

A

The overall vapour pressure of a solution depends on the vapour pressure of each component in a solution i.e. addition of a non volatile solute lowers the overall vapour pressure

38
Q

What does addition of solute do to boiling point according to Raoults law?

A

BP occurs when SVP reaches atmospheric pressure. Adding non-volatile solute lowers SVP, therefore a higher temperature is required to reach boiling point.

39
Q

What does adding 1 mole of solute to a kg of water elevate the BP by?

A

0.51 deg c (potatoes cook quicker when salt added)

40
Q

What temp does water boil at on Everest?

A

Water on Everest boils at 60deg, so an egg would take forever to cook

41
Q

What does adding 1 mole of solute do to the freezing point of 1kg of water and why?

A

Reduces the freezing point by 1.86 deg c, which is why salt is put on ice.

This is due to the regular matrix molecular structure that is formed when ice is made, being disrupted by the solute.

42
Q

What does adding 1 mole of solute do to the vapour pressure of 1kg of water?

A

Reduces by 0.04 kPa

43
Q

What does adding 1 mole of solute do to the osmotic pressure of 1kg of water?

A

Elevates it by 2261 kPa

Physics (15 decks)

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