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What is compressibility factor (Z) ?(i) deviation factor (Z = 1 )(ii) Z gt 1(iii) Z lt 1(iv) deviation graph and (v) relation between molar volume and Z. |
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Answer» Solution :Compressibility factor (Z) : Deviation between real gas and idea gas is known as compressibility factor (Z). `Z=(pV)/(nRT) ""`…..(Eq. -i) where, Z = 1 Z = Compressibility factor of ideal gas deviation BEHAVIOUR, `Z =(V_("real"))/(V_("ideal"))=("real molar volume")/("ideal molar volume")` .......(constant T) For `Z = 1, Z gt 1, Z lt 1` is give in points(i), (ii), (iii) (i) Z = 1 OR 1 deviation factor : For ideal gas Z = 1 at all TEMPERATURE and pressure , because pV = nRT. If Z = 1 then gas is ideal gas and `Z to p` graph is parallel line. At very low pressures all gases shown have Z = 1 and behave as an ideal gas. Ideal gas law, follow at Z = 1 at Boyle temperature of Boyle point at real pressure. (ii) `Z gt 1` OR Positive deviation : At high pressure all real gases shows `Z gt 1` they are less compressible than ideal gas. If `Z gt 1` than permanently gas. `N_(2), H_(2)O_(2)` shows positive deviation, `Z to p` graph SHOW positive deviation. According to diagram for `H_(2)` gas at high pressure `Z gt 1`. When pressure increases value of Z becomes more positive. Ideal gas shows positive deviation of higher than Boyle.s point and value of a are higher than are then intermolecular attraction force are weak. (iii) `Z lt 1` OR negativedeviation : At intermediate pressure, most gasses have `Z lt 1`. For `O_(2), CH_(4), CO_(2)` gas shows negative deviation, `Z to p` graph shows negative deviation. According to diagram, `Z lt 1` at lower pressure. Initially pressure increases than Z decreases, after that z cross ideal gas line. At lower temperature then Boyle.s point value of Z decreases at increases pressure, which REACTED at minimum value and pressure is continuously increases. (iv) Graph between `Z to p` for some gases :  (v) Relation between Z real gas and ideal molar volume : `Z = (pV_("real"))/(nRT) ""`.....(Eq. -i) If gas is an ideal, `V_("real")=(nRT)/(p) ""`......(Eq. -iii) Value of `(nRT)/(p)` is put in (iv) then we get equation (iii). `Z=(V_("real"))/(V_("ideal")) ""`....(Eq. -v) `THEREFORE Z =("Real molar volume")/("Ideal molar volume")`......(constant T) ..Compressibility factor is ratio of real molar volume and ideal molar volume... |
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