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PharmCH 1 > Solutions > Flashcards

Solutions Flashcards

1
Q

What is a solution?

A

A mixture of two or more substances - solid-solid, solid-liquid, etc

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2
Q

What is molarity?

A

Molarity is the number of moles of solute per litre of solution. …
• M = no of moles litre of solution

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3
Q

Unit of molarity

A

mol/dm^3

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4
Q

Mass concentration

A

Molarity x Molar mass

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5
Q

Molar concentration

A

Mass conc / Molar mass

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6
Q

What is molality?

A

Molality, is a measure of the concentration of a solute in a solution in terms of the amount of substance in a specified amount of mass of the solvent.

Conc of solute = Molality
Amount of substance in mass of solvent = Formula

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7
Q

Unit of molality

A

The unit for molality is expressed as ‘m,’ molal, or moles per kilogram.

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8
Q

Formula of molality

A

Molality, or molal concentration , m, is the number of moles of solute per kilogram of solvent.

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9
Q

The molality of a solution is always greater than the molarity

A

True

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10
Q

Molality changes with temperature. True or False

A

False

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11
Q

Which is a more accurate way of measuring solutes in solution in dynamic conditions?

A

Molality

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12
Q

Uses of molality

A
  • To compare and
    determine colligative properties of solutions
  • Measurement of solute conc in dynamic conditions
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13
Q

What are colligative properties?

A

Colligative properties of solutions are properties that depend upon the concentration of solute molecules or ions, but not upon the identity or nature of the chemical species or solute.

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14
Q

Examples of colligative properties

A

Boiling point
Vapour pressure
Freezing point
Osmotic pressure

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15
Q

Mass of solution

A

= Solute + Solvent

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16
Q

Normality (N) is dependent on the reaction. True or false?

A

True

17
Q

Formula for normality

A
  1. Equivalent weight per liter of solution

2. Molarity x Equivalent number

18
Q

What is the equivalent number?

A
  1. no of electrons or protons transferred in reactions
  2. valence state of an element or compound
  3. In acids and bases , the no. of hydrogen ions transferred (H+) or hydroxyl (OH) ions
19
Q

Why is normality so important?

A

It helps to determine the strength between acids or solvents

20
Q

What is equivalent weight?

A

Equivalent weight is the molar mass divided by the no. of equivalent number.

21
Q

The strength of a solution is described by:

A 
Normality
Molarity
 Molality
Equivalent mass
Strength of solution
Percentage concentration
22
Q

A normal solution is…

A

…one containing 1g equivalent of the dissolved solute in 1 litre of its solution

23
Q

Normality depends on…

A

Dilution

Temperature

24
Q

The equivalent weight of a substance is…

A

…the mass in grams of that substance which combines or reacts with a standard weight of a reference element or compound.

25
Q

If the equivalent weight of a substance, is the same as the molecular weight of that substance which combines or reacts, then…

A

…normality = molarity

26
Q

What is concentration?

A

It is the amount of solute dissolved in a solvent to make a solution. It can be dilute or concentrated.

27
Q

Concentration in Physical Units

A

➢% w/v
➢% w/w
➢% v/v

28
Q

What is standardization?

A

Standardization is the process of determining the exact concentration (molarity) of an unknown solution.

29
Q

Why is it important to standardise solutions?

A

●Reagents for assay must be of high purity
●Solutions concentration must be known before use
●For accuracy

30
Q

A standard solution is…

A

…a solution containing a precisely known concentration of an element or a substance.

31
Q

Examples of a primary standard

A

Anhydrous Sodium Carbonate Na2CO3
•Sodium chloride NaCl
•Potassium Dichromate K2Cr2O7
•Potassium Hydrogen phthalate (KHP) KHC8H4O4.

32
Q

Properties of a primary standard

A
  • Must be very pure
  • Should not be affected by exposure to moisture or air (non-hygroscopic)
  • Should maintain purity during storage
  • Rxns involving it must be stoichiometric and fast
  • High molecular and equivalent weight
33
Q

A secondary standard is…

A

…a solution whose unknown accurate concentration has been determined (standardised) while using a primary standard of known concentration and purity.

34
Q

Examples of secondary standard

A
  • Potassium permanganate, KMnO4
  • Sodium hydroxide, NaOH
  • HCl
  • EDTA - Ethylenediamminetatraacetic acid
35
Q

Properties of a secondary standard

A
  • Concentration can’t be calculated using regular molarity parameters
  • Exact conc determined by titration against a primary standard
  • Not very pure
  • More reactive
  • Used specifically for certain analyses
36
Q

Why is KMNO4 unsuitable as a primary standard? But as a secondary standard

A

It is a good oxidizing agent so it is reactive and less stable. More often, due to its reactivity, its own oxidized product, manganese oxide (MnO2), contaminates the content.

37
Q

What is the factor of a solution?

A

It is the relation of the exact strength of a solution to its nominal strength and is defined as the number of milliliters of exact (actual) strength which is equivalent to 1 ml of the solution of its nominal strength

38
Q

Formula for factor

A

Actual strength / Nominal strength

39
Q

Typical situations when you might use normality include

A

Acid-base chemistry
Redox reactions
Precipitation reactions

PharmCH 1 (3 decks)

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