JSUNIL TUTORIAL. 6. Gay lussac s Law : At constant V, The pressure of fixed amount of gas varies directly with its absolute temperature.

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1 CHAER 5 SAES OF MAER. Change in state : It is over all effect of Intermolecular forces, molecular Interactional energy & thermal energy:. Measurable properties of gases :,,, n, iscosity, specific heat are some measurable properties. 3. Gas Laws : he quantitative relationship b/w any two of the variables (, n,,) when other two are constant. 4. Boyle s Law : he pressure of fixed msss of gas varies inversely with the volume at constant. α /(n, const.) = 5. Charle s Law : At constant, the volume of fixed amount of gas varies directly with its absolute temperature. α or cons tant, 6. Gay lussac s Law : At constant, he pressure of fixed amount of gas varies directly with its absolute temperature. α or const, 7. Ideal gas equation : he relationship b/w, and by Gas Laws = nr. 8. Avogadro s Law : At given and, the volume of gas varies directly to the amount of gas. α n (, constant) 9. Dalton s Law of partial persure : he pressure enerted by a mixture of non reacting gases is equal to the sum of their partial pressure at constant (,) JSUNIL UORIAL 73

2 (total ) = (,, constant) 0. Kinetic Molecular theory : a. Gases consist of large number of identical particles (atoms or molecules) that are so small that the actual volume of the molecules is negligible in comparison to the empty space between them. b. here is no force of attraction between the particles of a gas at ordinary temperature and pressure c. articles of a gas are always in constant and random motion d. ressure is exerted by the gas as a result of collision of the particles with the walls of the container e. Collisions of gas molecules are perfectly elastic f. At any particular time, different particles in the gas have different speeds and hence different kinetic energies g. Average kinetic energy of the gas molecules is directly proportional to the absolute temperature. Real Gases : he gases which deviates from Ideal behavior at higher pressure and low temperature b/c of force of attraction b/w molecules increases.. Compressibility factor (Z) : It determine extent of devation of real gases from Ideal gas behavior : Z = gas Z=, for Nonideal gas Z<, Z > n. R.. n a 3. ander waal s Equation : nb nr. for ideal 4. Critical emperature : (c) he temperature above which a JSUNIL UORIAL gas cannot be liquefied whatever high pressure may be 5. Critical ressure : he minimum pressure required to liquity a gas at its critical temperature. 6. Critical olume : he volume of mole of gat at c, c. 7. Super cooled liquids : he liquids which are cooled to a temperature below its freezing point without freezing. 74

3 8. Elastic Collision : he collisions in which no loss of K.E. only there is transfer of energy. 9. apour pressure : he equilibrium pressure by vapour of liquid in a container at given temperature () 0. At higher altitude : he b.p. of water decreases b/c the atmospheric pressure is less than one atmosphere.. Surface ension () : It is force acting per unit length perpendicular to the line drawn on the surface : (Nm - ) : It decreases with increases in, it increases with increase in external pressure, b/c of it falling drops of liquid are spherical, liquid in capillary tube rises.. iscosity (η) : It is resistance offered to the flow of liquid dv due to friction b/w layer of fluids. F n. A. dn 3. Effect of & on viscosity : It decreases with increase in, and increases with increase in. 4. Low M.. & B.. of molecular liquids is due to low magnitude of molecular interaction energy. One mark questions. At what condition surface tension vanishes?. Why Helium is used in balloons in place of hydrogen? 3. At what temperature below which a gas does not obey ideal gas law? 4. At what temperature the volume of a gas is supposed to be zero? 5. What is the molar volume at 0 o C and bar pressure? JSUNIL UORIAL 75

4 6. Name the temperature above which a gas cannot be liquefied by any amount of pressure. 7. What is the effect of increase of temperature on surface tension and viscosity in a liquid? 8. How is the partial pressure of a gas in a mixture is related to the total pressure of the gaseous mixture? 9. Why vegetables are cooked with difficulty at hill station. 0. What is the value of Z (compressibility factor) for an Ideal gas? wers to One mark questions At critical temperature, meniscus b/w liquid and vapours disappears.. He is incombustible, though heavier than H. 3. Below Boyle emperature. 4. At absolute zero (O K) temperature. 5. It 400 ml. 6. It is critical temperature (c) 7. Both decreases with increase in temperature 8. = X x (total) 9. At hill station the atmospheric pressure is less and so boiling point decreases. 0. For ideal gas Z=. JSUNIL UORIAL wo Marks Questions Q. How do you convert pressure in atmosphere in to SI unit. 76

5 Q. What type graph will you get when is plotted against at constant temperature. Q.3 What would have happened to the gas if the molecular collisions were not elastic? Q.4 At a particular temperature, why vapour pressure of acetone is less than of ether? Q.5 Why liquids diffuse slowly as compared to gases? Q.6.. What would be the SI unit for quantity? n Q.7 In terms of Charle s law explain why -73 o C is the lowest temperature? Q.8 For real gases the relation b/w,, is given by vander Waal s equation, write it for n moles? Q.9 What correction is applied to obtain pressure of dry gas with the total pressure & aqueous tension? Q.0 Name two phenomena that can be explained on the basis of surface tension. wers to two marks questions. atm = 035 a or Nm -, bar = 0 5 a..a straight line parallel to pressure axis. 3. On every collision there is loss of energy, so molecules JSUNIL UORIAL would have slowed down & settled down in vessel and pressure reduce to O. 4. b/c molecular force of attraction in acetone is stronger than those present in ether. 77

6 5. In liquids the molecules are less free than in a gas. i. e intermolecular forces in liquid are greater than in gas. 3.. N. m ( m ) ( K) 4 6. N. m k mal n mal 7 At -73 o C, the olume of gas becomes equal to zero i. e. gas ceases to exist. 8. ander waal s equation 9. n a v nb n. R.. (dryygas) = (otal) Aqueous tension 0. Surface tension can explain (i) capillary action. (ii) Spherical shape of small drops of liquid. hree Marks Questions Q. Calculate temperature of 4.0 moles of gas occupying 5dm 3 volume at 3.3 bar. (R= bar dm 3 k - mol - ) nr, or nr bar x 5dm Or mol x 0.083bar dm k mol Q ml of phosphorus vapours weight 0.065g at 543 o C and bar pressure what is molar mass of phosphorous?. x34.05, (54b 73) x v 73 JSUNIL UORIAL at 0 Or =.35 ml Now.35 ml of vapours at 0 o C and bar pressure weight gm o C 78

7 Now 700 ml of vapors at 0 o C and bar pressure weight x Q.3 A mixture of dihydrogen and dinitrogen at bar pressure contains 0% by weight of H. Calculate partial pressure of H. he mixture of H and O contain 0% H means 0 gm H & 80gm O 0 80 n (H ) = 0moles, n( O ).5contest. 3 (H) = n( H ) n( H ) n( ) 0 x ( total ) x bar 0. 8bar 0.5 Q.4 What will be minimum pressure required compressing 500dm 3 of air at bar to 00 dm 3 at 30 o C?. = bar. = 500dm 3 =? =00 dm 3 & temp. constant 30 o C So by Boyle s low = 500 x 500 = x 00 or.5 bar 00 Q.5 Calcutate the total pressure in mixture of 4g of O and gm. Of H can fixed to a total volume of IL at 0 o C. (R = 0.08) Latm. Mol - JSUNIL UORIAL no nh x R x 73 = x.4 5. atm. 3 8 Q.6 Account for the following : 79

8 (i) he size of weather balloon becomes longer and larger as it ascend up into higher altitudes. (i) At higher altitudes atmospheric pressure decreases, but inside the balloon gas exerts pressure and size becomes larger. Q.8 What do you mean by ideal gas and real gas? Why do real gases deviate from ideal behaviors?. Ideal gas follows gas laws at all & Real gas donot gas laws at all &. Real gas deviate from ideal behaviour due to force of attraction and because of volume of molecules of gases are not negligible. Q.9 Using the equation of state =nr Show that at given, density of gas proportional to gas pressure. n n R. R v m m R,, R... M M R. M R x M ( Where const. m ) v JSUNIL UORIAL Q.0 Critical temperature of CO and CH 4 gases are 3. 0 C and C respectively. Which of these has strong intermolecular forces & why? CO has strong vander waal s forces of attraction than CH 4. b/c of greater polarity and high molecular wt. 80

9 Hots Questions with wers. Q. (a)why aerated water bottles kept under water during summer? (b) Which property of liquid is responsible for spherical shape of drop? (c) Why is moist air lighter than dry air? (d) Define aqueous tension? (e) What is units of a and b which are vander waal s constant? (a) o reduce temperature so to reduce pressure, other wise bottle may burst. (b) Surface ension. (c) Moist air has water vapours which lowers vapour density, so it is lighter. (d) It is pressure of water vapours at given. (e)unit of a in atm. L mol -, b is L mol -. Q. Why does sharpened edge becomes smooth on heating up to melting point? On heating the glass it melts and take up rounded shape at edges which has minimum surface area. b/c of surface tension. Q.3 Arrange following in order of increasing density: d M 0 0 0, O at 5 C, atm, O at O C, atm, O at73 C, atm. R M d, R, M are constant, so d depends upon so at 5 0 C, R Atm, 98 At 73 o C, atm 546 density will be: O at 73 0 C, atm < O at 5 0 C, atm. Hence increasing order of Q.4 An O cylinder has 0L O at 00 atm. It patient takes 0.50ml JSUNIL UORIAL of O at atm in one breath at 37 0 C. How many breaths are possible? 0L at 00 atm =? L at atm,, 00 x0 x or otal olume olume for breath 000 L x0 L 6 = 000 L, No of breathes = 4 x 8

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Visit For All NCERT solutions, CBSE sample papers, Question papers, Notes for Class 6 to 12 V T P T. const, T isit www.ncerthelp.com For All NCER solutions, CBSE sample papers, Question papers, Notes for Class 6 to CHAER 5 SAES OF MAER. Change in state : It is over all effect of Intermolecular forces, molecular