Abnormal Molar Mass Quiz and Flashcards

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Questions and Answers

What is the term used to describe a substance showing abnormal molar mass?

Abnormal molar mass substance

Anomalous substance (correct)

Abnormal solute

Colligative compound

Which expression represents the elevation of boiling point in terms of van’t Hoff factor?

Tb = i Kb m (correct)

Tb = i Kb n2 m

Tb = i n1 n2 Kb m

Tb = n1 i Kb m

In the Clausius-Clapeyron Equation, what does (p2/p1) represent?

Final pressure/initial pressure (correct)

Initial pressure/final pressure

Partial pressure ratio

Change in pressure

What will happen to the van’t Hoff factor (i) when a solute undergoes association in a solution?

i < 1 Signup and view all the answers

How is the abnormal molar mass of a substance determined?

By studying colligative properties Signup and view all the answers

What property of a liquid increases with the increase in temperature according to the text?

Vapour pressure Signup and view all the answers

What does w3 represent in the context of the text?

Increase in weight of the third vessel due to absorption Signup and view all the answers

Which formula is used to calculate mass by volume percentage?

$\frac{W_B}{V} \times 100$ Signup and view all the answers

What is the unit for parts per million (ppm) in solutions?

$\frac{mg}{L}$ Signup and view all the answers

In the relation $xA + xB = 1$, what do xA and xB represent?

Mole fraction of solvent and solute respectively Signup and view all the answers

What is the relationship between Molarity (M) and Normality (N) as per the text?

$N_A \times M = N \times M_B$ Signup and view all the answers

What does GEM stand for in the context of the text?

Gram Equivalent Mass Signup and view all the answers

In an ideal solution, what is the relationship between the intermolecular attractive forces of A-A, B-B, and A-B?

A-A = A-B = B-B Signup and view all the answers

Which type of solutions show a pressure composition curve with negative deviation from Raoult's Law?

Non-ideal solutions with negative deviation Signup and view all the answers

What is one characteristic of non-ideal solutions showing positive deviation from Raoult's Law?

'HMIXING > 0, 'VMIXING > 0 Signup and view all the answers

What type of mixtures are azeotropes?

Mixtures having the same composition in liquid and vapor phase Signup and view all the answers

In the determination of molar mass, which type of solutions form minimum boiling azeotropes?

Solutions with negative deviation from Raoult's Law Signup and view all the answers

What is the molar mass of a substance if its solubility in a specified amount of solvent is the maximum amount that can be dissolved?

$Molar \ mass = \frac{Amount \ dissolved}{Solubility}$ Signup and view all the answers

Study Notes

Colligative Properties

Abnormal molar masses are observed when the molecular mass of a substance determined by studying colligative properties is different from the theoretically expected value.
Van't Hoff factor (i) is used to calculate the extent of association or dissociation of a solute in a solution.
i = total number of moles of particles after association (dissociation) / number of moles of particles before association (dissociation)

Vapour Pressure

Vapour pressure increases with increasing temperature.
Clausius-Clapeyron equation: ln(p2/p1) = (ΔHvap/R) (1/T1 – 1/T2), where ΔHvap is the enthalpy of vaporisation of the liquid.
Relative lowering of vapour pressure of a solvent can be calculated using the formula: pSolution = pSolvent - (w1 - w2) / w3.

Solutions and Colligative Properties

Important formulae:
- Mole fraction of A (xA) = nA / (nA + nB)
- Mole fraction of B (xB) = nB / (nA + nB)
- Molarity (M) = moles of solute / volume of solution in litres
- Molality (m) = moles of solute / mass of solvent in kg
- Normality (N) = gram equivalents of solute / volume of solution in litres
- Normality × Equivalent mass (solute) = Molarity × Molar mass (solute)

Properties of Solutions

Ideal solutions:
- ΔHmixing = 0
- ΔVmixing = 0
- Intermolecular attractive forces between A-A and B-B are nearly equal to those between A-B
Non-ideal solutions:
- Do not obey Raoult's law over the entire range of concentration
- ΔHmixing > 0 or ΔHmixing < 0
Azeotropes:
- Binary mixtures having the same composition in liquid and vapour phase
- Boil at a constant temperature
- Form minimum or maximum boiling azeotropes depending on the composition

Solubility

Solubility of a solid in a liquid is its maximum amount that can be dissolved in a specified amount of solvent.

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Description

Explore the concept of abnormal molar masses in chemistry, particularly in relation to colligative properties such as relative lowering of vapor pressure, elevation of boiling point, and depression of freezing point. Understand how abnormal molar masses can affect the determination of molecular mass of substances.

Abnormal Molar Masses and Colligative Properties