Ch 9Solutions — Class 11 Chemistry, concept-first.

Look closely at almost anything around you -- sea water, the air you breathe, even a brass fitting -- and you'll find it is rarely a pure substance.

We can survive weeks without food, but a close look at almost anything around us -- a bottle of mouthwash, sea water, the air we breathe, even a piece of jewellery -- shows it is rarely a pure substan…

A solution is a homogeneous mixture of two or more substances, made up of atoms, ions or molecules distributed uniformly throughout.

Everyday products come labelled with a concentration -- a chlorhexidine mouthwash might say 0.2% (w/v), commercial hydrogen peroxide is typically 3% (w/v), tap-water purity is reported in ppm (parts p…

A standard solution (or stock solution) is one whose concentration is known accurately. It is prepared by weighing out a precisely known amount of solute and transferring it to a standard (volumetric)…

Working from a concentrated stock solution and diluting it as needed, rather than weighing out a fresh dilute solution every time, has three practical advantages:

Solubility of a solute is the maximum amount of that solute that can be dissolved in a specific amount of solvent, at a specified temperature.

Solubility depends on several factors: the chemical nature of the solute and solvent, the temperature, and (for gases) the pressure.

William Henry studied how the solubility of a gaseous solute in a particular solvent depends on pressure.

Henry's law is a useful approximation, not a universal law -- it has well-defined limits:

Liquids have an inherent tendency to evaporate: if a molecule at the liquid's surface has enough kinetic energy to overcome the intermolecular forces of attraction holding it in the liquid, it escapes…

When a solute -- whatever its physical state (solid, liquid or gas) -- is dissolved in a liquid solvent, the result is a liquid solution.

Consider a binary liquid solution formed by dissolving a volatile liquid solute A in a pure liquid solvent B, in a closed vessel.

Now consider the other important binary case: a nonvolatile solute dissolved in a volatile liquid solvent.

Every binary liquid solution can be classified by how closely it follows Raoult's law across the entire range of composition -- from pure A, through all intermediate mixtures, to pure B.

An ideal solution is one in which every component -- both the solute and the solvent -- obeys Raoult's law across the entire range of concentration, not just when dilute.

A non-ideal solution fails to obey Raoult's law across the whole concentration range, and unlike an ideal solution, it shows a measurable change in both enthalpy and volume on mixing: and .

Six distinct factors can drive a solution away from ideal behaviour:

Pure water is tasteless; add sugar and it becomes sweet, add salt and it becomes salty. This shows that a solution's properties generally do depend on the chemical nature of the dissolved solute parti…

The vapour pressure of a solution containing a nonvolatile, non-electrolyte solute is always lower than the vapour pressure of the pure solvent alone (this was already derived from Raoult's law in sec…

A liquid's boiling point is the temperature at which its vapour pressure becomes equal to the atmospheric (external) pressure, conventionally 1 atm.

Freezing point is defined as the temperature at which the solid and liquid states of a substance have the same vapour pressure -- i.e. the solid and liquid phases are in equilibrium.

Osmosis is a spontaneous process central to many biological systems: solvent molecules pass through a semipermeable membrane, moving from a solution of lower solute concentration into a solution of hi…

In the ordinary osmosis apparatus of section 9.9.4, pure water spontaneously moves through the semipermeable membrane into the NaCl solution side.

The molar mass of a nonvolatile solute can, in principle, be calculated accurately from any of the four colligative properties (sections 9.9.1-9.9.4).

Association. In certain solvents, solute molecules bond together to form dimers, trimers, or larger aggregates, rather than remaining as separate independent molecules.

To quantify exactly how much a solute's association or dissociation shifts the observed (abnormal) molar mass away from its true value, van't Hoff introduced a factor, denoted and now called the van't…

- A solution is a homogeneous mixture of two or more chemically non-reacting substances, mixed uniformly; the component present in the larger proportion is the solvent, the lesser component is the sol…

The textbook's own flow chart is headed Solutions, and fans out along several branches:

The end-of-chapter evaluation set, printed directly from the textbook in two parts. The first part, "Choose the Best Answer" (30 multiple-choice questions, one explicitly sourced from NEET), tests con…

Sample papers and previous-year board questions for this subject.