State Of Matter And Solution Flashcards
What is osmotic pressure?
The osmotic pressure is defined as the excess mechanical pressure required to be applied to a solution separated by a semipermeable membrane from pure solvent or a dilute solution to prevent the osmosis or free passage of the solvent molecules at a given temperature. The osmotic pressure is a colligative property.
A solution concentration is expressed in molarity and not molality while considering osmotic pressure. Why?
While calculating osmotic pressure by equation, π = CRT, the concentration is expressed in molarity but not in molality.
This is because the measurements of osmotic pressure are made at a certain constant temperature.
Molarity depends upon temperature but molality is independent of temperature.
Hence in osmotic pressure measurements, concentration is expressed in molarity.
What is van’t hoff factor ?
Definition of the van’t Hoff factor, i : It is defined as a ratio of the observed colligative property of the solution to the theoretically calculated colligative property of the solution without considering molecular change.
State Raoult’s law for a solution containing a nonvolatile solute.
Statement of Raoult’s law : The law states that the vapour pressure of a solvent over the solution of a nonvolatile solute is equal to the vapour pressure of the pure solvent multiplied by mole fraction of the solvent at constant temperature.
What is the effect on the boiling point of water if 1 mole of methyl alcohol is added to 1 dm3of water? Why?
The boiling point of water (or any liquid) depends on its vapour pressure.
Higher the vapour pressure, lower is the boiling point.
When 1 mole of volatile methyl alcohol is added to 1 dm3 of water, its vapour pressure is increased decreasing the boiling point of water.
Which of the four colligative properties is most often used for molecular mass determination? Why?
Since osmotic pressure has large values, it can be measured more precisely.
The osmotic pressure can be measured at a suitable constant temperature.
The molecular masses can be measured more accurately.
Therefore, it is more useful to determine molecular masses of expensive substances by osmotic pressure.
What are isotonic, hypotonic and hypertonic solutions?
Isotonic solutions : The solutions having the same osmotic pressure at a given temperature are called isotonic solutions.
Hypotonic solutions : the more dilute solution exhibiting lower osmotic pressure is said to be hypotonic.
Hypertonic solutions : When two solutions have different osmotic pressures, then the solution having higher osmotic pressure is said to be a hypertonic solution with respect to the other solution.
Explain reverse osmosis
Reverse osmosis : The phenomenon of the passage of solvent like water under high pressure from the concentrated aqueous solution like seawater into pure water through a semipermeable membrane is called reverse osmosis.
The osmotic pressure of seawater is about 30 atmospheres. Hence when pressure more than 30 atmospheres is applied on the solution side, regular osmosis stops and reverse osmosis starts. Hence pure water from seawater enters the other side of pure water.
For this purpose of suitable semipermeable membrane is required which can withstand high pressure conditions over a long period.
This method is used successfully in Florida since 1981 producing more than 10 million litres of pure water per day.
Why vapour pressure of a solvent is lowered by dissolving a nonvolatile solute into it?
When a nonvolatile solute is added to a pure solvent, the surface area is covered by the solute molecule decreasing the rate of evaporation, hence its vapour pressure decreases. This decrease in vapour pressure is called lowering of vapour pressure.
If P0 is the vapour pressure of a pure solvent (liquid) and P is the vapour pressure of the solution, where P < P0, then, (P0 – P) is the lowering of the vapour pressure.
What is Raoult’s law?
It states that the partial vapour pressure of any volatile component of the solution is equal to the vapour pressure of the pure component multiplied by its mole fraction in the solution
What makes an ideal solution
1) obeys Raoult’s laww
2) no heat exchange when mixed together
3) no volume change when mixed together
4)
Define Unit cell
The smallest repeating structured unit of a crystalline solid is called unit cell
Define Lattice
Lattice is a geometrical arrangement of points in a three dimensional periodic array
Name an element which can be added to silicon to give a –
(i) p – type semiconductor
(ii) n – type semiconductor.
(i) For p – type semiconductor Boron can be added.
(ii) For n – type semiconductor, Phosphorous can be added.
What is the difference between ferromagnetic and paramagnetic substances?
A ferromagnetic substance has permanent magnetic behaviour whereas a
paramagnetic substance acts as a magnet only in the presence of an external magnetic field.
