An important facility for 11th class students preparing for short questions chemistry 11th class chapter nine of BISE. Get hundreds of questions to prepare and get better marks in 11th chemistry
0
Our database contains a total of 0 questions for chemistry Short Questions. You’ll prepare using this huge databank.
Question: 1
Answer: 1
1-41
Question: 2
The concentration in terms of molality is independent of temperature but molarity depends upon temperature .Why?
Answer: 2
2-41In molality mass of solvent is taken.Mass us independent of temperature.In molarity volume of solution is take.Volume changes by change in temperature.
Question: 3
One molal solution of urea in water is dilute as compared to one molar solution of urea but the number of practices of solute is same.Justify it?
Answer: 3
3-41Both one molar and one molal urea solution contains equal number of molecules(6.022x1023 ).Number of water molecules are different in both cases.One molal solution contains 1000g or 55.5 moles of water.One Molar solution has less number of water molecules than one molal.
Question: 4
Polar solids are not dissolved in on-non-polar solvent,give reason?
Answer: 4
4-41There is a general principal that "like dissolve like".That;s why polar compounds are not dissolve in non-polar solvent because their nature matches with each other.
Question: 5
What is critical solution temperature? Give the critical solution temperature of phenol water system?
Answer: 5
5-41Critical Temperature: The temperature at which two conjugate solutions merge into each other to form homogeneous mixture is called critical solution temperature or consulate temperature.
Phenol-Water system has critical temperature of 65.9°C at which two conjugate solution merge into one another.
Question: 6
Differentiate between zeotropic and azeotropic mixture?
Answer: 6
6-41Zeotropic Mixtures: The liquid mixtures which distills with change in composition is called zeotropic mixtures,e.g.Methyl Alcohol-water solution.
Azeotropic Mixtures: The liquid mixtures which boil at constant temperature and distill over without changes in composition like a pure compound at any temperature is called azeotropic mixtures.eg, HCI formsazeotropic with water.
Question: 7
Define fractional crystallization.How is it useful?
Answer: 7
7-41Fractional Crystallization: The separation of solid substances from a solution one by one on cooling is called fractional crystallization.This technique is used for separation of impurities from sample.
Question: 8
Define consulate solution temperature with example (what is consulate temperature)?
Answer: 8
8-41Consulate Temperature: The temperature at which two conjugate solutions merge into each other to form homogeneous mixture is called critical solution temperature or consulate temperature.e.g Water -Aniline has consulate temperature 167°C with 15% H2O.
Question: 9
Calculate percentage by weight of NaCI when 2g of NaCI is dissolved in 20g of water?
Answer: 9
9-41Mass of NaCl =2g
Mass of water =20g
Mass of solution= 20+2=22g
%by weight of NaCl=2/22x100=9.09%
Question: 10
Define azeotropic mixture.Give two examples?
Answer: 10
10-41Azeotropic Mixtures: The liquid mixtures which boil at constant temperature and distil over without changes in composition like a pure compound at any temperature is called azeotropic mixtures.e.g.HCI azeotropic mixture with water.
Question: 11
One molal solution of urea is more dilute as compared to its one molar solution.Why?
Answer: 11
11-41One molal solution contains one mole of urea per kg of solvent, while one mole solution contains one mole of urea per one dm3 Of solution.In one molal solution amount of water is greater than one molar solution because amount of solution included in it.
Question: 12
Define percentage weight/weight.Give an example?
Answer: 12
12-41
Question: 13
Give two examples of liquid solution?
Answer: 13
13-41- Alcohol in water
- Benzene in toluene
Question: 14
Why the non-ideal solutions do not obey the Raoult's law?
Answer: 14
14-41Mnay solutions do not behave ideally as they show deviation from Raoult's law due to difference in their molecular structure I.e. Size, shape and intermolecular forces.During their formation change in volume and enthalpy take place.Hence they show deviation from ideality.
Question: 15
Differentiate between continuous and discontinuous solubility curves?
Answer: 15
15-41Continuous Solubility Curve: These are smooth curves and do not show any sharp break points.(Continuous increase or decreases in solubility with temperature.e.g.Solubility curves of KCIO3,K2Cr2O7 Etc.
Discontinuous Solubility Curves: These are not smooth and shows sudden breaks due to sudden changes in solubilities.e.g.Solubility curves of Na2SO4,CaCl2 etc.
Question: 16
Define solubility giving one example?
Answer: 16
16-41The solubility is defined as the concentration of the solute in the solution when it is in equilibrium with the solid substance at a particular temperature. Solubility is expressed in terms of number of grams of solute in 100g of solvent. At a particular temperature, saturated solution of NaCl in water at O° C contains 37.5g NaCl in 100g of water.
Question: 17
Why the solubility of glucose increases on increasing temperature?
Answer: 17
17-41When glucose is dissolve in water it show endothermic heat of solution.Solute molecules separate from each other to dissolve in solvent.This process required energy.So when temperature is increased solubility also increases.
Question: 18
Fractional crystallization technique is used to purify the chemical products.Justify?
Answer: 18
18-41The separation of solid substance from a solution one by one on cooling is called fractional crystallization.Solubilities depends upon temperature.
E.g.Solubility of KNO3 Rapidly changes with temperature but solubility of KCI and Kbr changes gradually.Thus one substance may precipitate earlier by cooling, leaving behind others.
Question: 19
Can sugar cannot be dissolved in benzene.Give reason?
Answer: 19
19-41Can-sugar is apolar covalent substance and it is soluble in polar solvent like water. Sugar dissolve in water due to the formation of H-bonding between solute-solvent,but not in benzene.As we simply say that solubility based upon principle"Like dissolves like".
Question: 20
The total volume of the solution by mixing 100 cm3 Of water 100 cm3 Of alcohol may not be equal to 200 cm3 Justify it?
Answer: 20
20-41Alcohol and water are mix in all proportions.However, the properties of such solutions are not strictly additive.Generally, the volume decreases ,mixing but in some cases it increases.Heat may be evolved or absorbed during the formation of such solutions.
Question: 21
What is upper consulate temperature and give one example?
Answer: 21
21-41The temperature of 65.9°C at which two conjugate solutions merge into one another is called critical solution temperature or upper consulate temperature .For Example 34% phenol and 66% water solution.
Question: 22
Define solubility curve.Name its two types?
Answer: 22
22-41Solubility Curve: A graphical representation between temperature and solubility of a substance is called solubility curve.These are of two types:
- Continuous solubility curve
- Discontinuous solubility cure
Question: 23
Differentiate between ideals and non-ideal solutions?
Answer: 23
23-41Ideal Solution:
- The solutions which obey Raoult's law are called ideal solution
- In these solution, enthalpy change is zero.
Question: 24
Give conjugate solution with one example.
Answer: 24
24-41Each liquide layer of solution of two liquids which are not miscible with each other is a saturated solution of the other liquid.Such solutions are called conjugated solutions.On shaking equal volumes of water and ether, two layers are formed which is example of conjugated solution.
Question: 25
Define Colligative properties.Name important colligative properties?
Answer: 25
25-41Colligative Properties: The properties of a solution which is based upon the number of solute particles and independent of the nature of solute is called colligative properties.Name of some colligative properties are:
- Lowering of vapour pressure
- Depression in freezing point
- Elevation in boiling point
- Osmotic pressure
Question: 26
NaCl and KNO3 Lowers the melting point of ice.Give reason?
Answer: 26
26-41When NaCl andKNO3 Is added to H2O , is vapour pressure is lowered. Due to lowering of vapour pressure, solution freezes below than the freezing point of water.Hence NaCl and KNO3 Is used to lower the melting point of ice.
Question: 27
Why is the vapour pressure of a solution less than pure solvent?
Answer: 27
27-41In pure solvent all the surface of solvent is covered by solvent molecules.But when a solute is added to it from a solution.Some surface is occupied by solute particles. Hence escaping tendency of solvent is decreases and thus vapour pressure of solution also lowered.
Question: 28
Beckmann's thermometer is used to note the depression in freezing point.Explain with reason?
Answer: 28
28-41There is a very small difference between freezing point of pure solvent and its dilute solution.Ordinary thermometer can read up to 0.5K.Hence theses cannot differentiate between freezing point of pure solvent and solution.
Beckmann' sthermometer can read up to 0.01K.Hence it cn exactly measure the freezing point of pure solvent and solution.
Question: 29
Boiling points of liquid are increased when solute is added to them.Give reason?
Answer: 29
29-41Because the vapour pressure of solvent decrease due to the pressure of solute.Therefore,we have to supply high temperature in order to equalized the vapour pressure of solvent to external pressure to boil it. This results in the increase of boiling point of solvent in the presence of solute.
Question: 30
State ebullioscopeic constant and cryoscopic constant?
Answer: 30
30-41Ebullioscopic constant: It is elevation in boiling point which is produced,when 1 mole of solute is dissolved in 1 kg of solvent.It is denoted by Kb. Its value is 0.52C° for water.
Cryoscopic constant: It is depression in freezing point which is produced when q mole of solute is dissolved in 1 kg of solvent. It is denoted by Kf
Its value is 1.86 C° for water
Question: 31
What are the names major parts of apparatus used in Landsberger's method for elevation of boiling point?
Answer: 31
31-41- An inner tube with a hole in its side.This tube is graduated.
- A boiling flask which send the solvent vapours into the graduated tube through a rosehead..
- An outer tube, which receives hot solvent vapours coming from the side hole of the inner tube.
- A thermometer which can read up to 0.01K.
Question: 32
Give the condition of colligative properties?
Answer: 32
32-41There are following conditions for colligative properties:
- Solution must be dilute.
- Solute must be non-volatile.
- Solute must be non-electrolyte.
Question: 33
Why some properties are called colligative properties?
Answer: 33
33-41Colligative properties are called so because these depend upon the number of solute particle in definite amount of solvent and independent on the nature of solute.For example lowering of vapour pressure of water, caused by the addition of 6g of urea, 18 g of glucose and 34.2 g of sucrose is same although the solute particles are of different nature but their numbers are same.
Question: 34
In summer the antifreeze solutions protect the radiations from boiling over.How?
Answer: 34
34-41The boiling point of liquid is increased by the addition of solute such as ethylene glycol in water.Therefore in summer the antifreeze liquids protect the water in car radiators from over boiling. Similarly the addition of a solute in water depress its freezing point. During winter it protect a car by preventing the liquid from freezing in radiators.
Question: 35
Describe that NaCI and KNO3 Are used to lower the melting point of ice?
Answer: 35
35-41NaCI and KNO3are used as antifreeze.They depress the freezing point of ice and it melts. This method is used to melt the ice from the roads in winter.
Question: 36
Colligative properties are obeyed when the solute is non-electrolyte and also when the solutions are dilute.Explain?
Answer: 36
36-41Colligative properties depend upon number of solute, particles in solution of non-electrolyte. Solute do not ionize in solution and its number of particles remain same. E.g1 mole of urea produces 3.02x1023 Particles in solution.When solution is dilute, less number of solute particles far away from each other and they behave independently and colligative properties are obeyed.
Question: 37
The freezing points are depressed due to the presence of solutes.Five reason?
Answer: 37
37-41Freezing point of a substance also related to its vapour pressure.it is a temperature at which there is equilibrium between a solid and a liquid. At freezing point, vapour pressure of liquid and solid phase is same.When some solute is added to solvent, its vapour pressure decreases and freezing point also decreases.
Question: 38
Define "heat of solution" and "hydration energy"?
Answer: 38
38-41The quantity of heat energy that is absorbed or released when a substance forms solution, is termed as heat of solution.
When ionic compound is dissolved in water, the first step is the separation of ions from solid and second step is separated ions are surrounded by solvent molecules.A Hydrated ion is attracted by the solvent dipoles and energy is released, so second step is exothermic. The energy given out by the second step is known as the hydration energy .
Question: 39
Define molal freezing point constant giving example.
Answer: 39
39-41It is depression of freezing point, when one mole of non-volatile and non-electrolyte solute is dissolved in one kg of solvent.
Question: 40
Why ethylene glycol is added in radiator of Automobile?
Answer: 40
40-41The most important application of this phenomenon is the use of antifreeze in the radiator of an automobile.The solute is ethylene glycol, which is not only completely miscible with water but has a very low vapour pressure and non-volatile in character. When mixed with water it lowers the freezing point a swell as raised the boiling point.
Question: 41
Why hydration energy of Na+ Ion is less than Li+ Ion?
Answer: 41
41-41Hydration energy of an ion depends upon two parameters .
- Ionic Radii
- Charge density
