Description : What will be the molar volume of nitrogen and argon at 273.15 K and 1atm pressure?
Last Answer : Ans. At 273.15K and 1atm pressure every gas has molar volume = 22.4L.
Description : (i)State why heat changes in physical and chemical processes are indicated by enthalpy changes and not by entropy changes? (ii)What are the limitations of First Law of thermodynamics?
Last Answer : (i) Most of the processes are carried out in an open system i.e, at constant pressure. (ii)(a) Can’t explain the feasibility of the reaction. (b)It poses no restriction on the direction of flow of heat. (c)Practically it is not possible to convert the heat energy into an equivalent amount of work.
Description : Account for the following properties of gases on the basis of kinetic molecular theory of gasesa) high compressibility b) gases occupy whole of the volume available to them.
Last Answer : Ans. a) High compressibility is due to large empty space between the gas molecules. b) Due to absence of attractive forces between the molecules, they can easily separate from one another.
Description : What is the sign of enthalpy of formation of highly stable compound?
Last Answer : Ans. Negative.
Description : Out of carbon(diamond)and carbon (graphite) whose enthalpy of formation is taken as zero?
Last Answer : Ans. Enthalpy of formation of carbon in the form of graphite is taken as zero because it is a more commonly found in stable form of carbon.
Description : Write an expression in the form of chemical equation for the standard enthalpy of formation (∆Hf) of CO (g).
Last Answer : Ans. C(s) +1/2 O2(g) → CO (g)
Description : What is meant by entropy driven reaction? How can the reaction with positive change of enthalpy and entropy be made entropy driven?
Last Answer : Ans.The free energy change of a reaction is given by ΔG = ΔH - TΔS For a reaction to be spontaneous, ΔG should be -ve. If both ΔH and ΔS are positive ΔG can be -ve if TΔS>ΔH in magnitude. Thus, entropy ... is low, TΔS should be greater than ΔH (ii) If ΔS is small, T should be so large that TΔS>ΔH.
Description : Give enthalpy (H) of all elements in their standard state.
Last Answer : Ans. In standard state enthalpies of all elements is zero.
Description : (i)What happens to the internal energy of the system. (a) if work is done by the system. (b)Work is done on the system. (ii) Why enthalpy of neutralization of strong acid and base is consant?
Last Answer : Ans. (i).(a)ΔU Decreases. (ΔU = q - w) (b)ΔU increases. (ΔU = q + w) (ii) Strong acids and bases dissociate completely into ions in aqueous solution and form 1 mole of water.
Description : The intensive properties are (A) Molar volume, density, viscosity and boiling point (B) Refractive index and surface tension (C) Both (A) and (B) (D) None of these
Last Answer : (C) Both (A) and (B)
Description : The extensive properties are (A) Volume, mass and number of moles (B) Free energy, entropy and enthalpy (C) Both (A) and (B) (D) None of these
Description : Heat and work are (a) point functions (b) system properties (c) path functions (d) intensive properties (e) extensive properties.
Last Answer : Answer : c
Description : Which of the following is not an intensive property? (A) Molar heat capacity (B) Internal energy (C) Viscosity (D) None of these
Last Answer : (B) Internal energy
Description : Chemical potential (an intensive property) of a substance is a force that drives the chemical system to equilibrium and is equal to its partial molar properties. The ratio of chemical potential to free energy of a pure substance ... temperature and pressure is (A) 0 (B) 1 (C) ∞ (D) None of these
Last Answer : (B) 1
Description : What will be the effect on equilibrium if (i) a catalyst is added to it (ii) An inert gas is added at constant volume
Last Answer : Ans. (i) The state of equilibrium is not disturbed on adding catalyst rather it is attained quickly. (ii) No effect on state of equilibrium
Description : Why excluded volume ‘b’ is four times the actual volume of the molecules?
Last Answer : Ans. The two molecules cannot come closer than distance 2r and the volume of sphere with radius 2r is four times the volume of one molecule.
Description : Explain the absolute zero (in terms of volume) with the help of isobar.
Last Answer : Ans: At absolute zero ,volume approach to zero and below this temperature, the volume will be negative, which is meaningless. Hence absolute zero is the lowest possible temperature .
Description : Why liquids do not have definite shape although they have definite volume?
Last Answer : Ans.Because inter molecular forces are strong enough to hold the molecules but not so strong as to fix them into definite position.
Description : Justify the statement. A gas neither has a fixed shape nor a fixed volume.
Last Answer : Gas molecules possess large intermolecular spaces therefore the cohesive forces between them are insignificant. This is why a gas has no fixed shape or volume
Description : What refers to the measure of the disorder present in a given substance or system? A. Enthalpy B. Entropy C. Heat capacity D. Molar heat
Last Answer : Entropy
Description : The change in physical size of a substance when its temperature changes. a. intensive property b. extensive property c. volume expansion d. thermal expansion
Last Answer : thermal expansion
Description : Under what condition, the heat evolved or absorbed in a reaction is equal to its free energy change?
Last Answer : Ans. As ΔG = ΔH – TΔS. Thus, ΔG = ΔH only when either the reaction is carried out at 0^0 K or the reaction is not accompanied by any entropy change, i.e., ΔS = 0
Description : Under what condition, the heat evolved/absorbed in a reaction is equal to its free energy change?
Last Answer : Ans. In ∆G = ∆H – T. ∆S, when reaction is carried out at 0 K or ∆S = 0, then ∆G = ∆H.
Description : (i)What are sign conventions used for Heat and Work? (ii).Neither ‘q’ nor ‘w’ is a state function but “ q + w” is a state function. Assign reason.
Last Answer : Ans. (i)Heat absorbed by the system = +ve Heat evolved by the system = -ve Work done by the system = -ve Work done on the system = +ve (ii)ΔU = q + w and ‘∆U’ is a state function, which depends upon initial and final states of the system and not upon its path.
Description : (i) Under what conditions is the heat absorbed by a system is equal to the work done by the system? (ii)In a process, 802 J of heat is absorbed by a system and 294 J of work is done by the system. What is the change in internal energy for the process?
Last Answer : (i) When ∆U=0 i.e, for isothermal process q = w (ii)ΔU = q + w ΔU = 802 + (-294) =508J
Description : State Hess’s law of constant heat summation.Give its two applications.
Last Answer : Ans. Hess's law states that enthalpy change for a reaction is same whether the reaction occurs in single step or several steps. OR If a reaction occurs in several steps then ,its standard enthalpy of ... the formation of the compound (ii) It is used to calculate Lattice enthalpy of an ionic solid.
Description : dW and dq are not the exact differential, because q and W are (A) State functions (B) Path functions (C) Intensive properties (D) Extensive properties
Last Answer : (B) Path functions
Description : What refers to the thermodynamic properties which are independent on the amount of the substance present? a. Extensive property b. Intensive properties c. Reversible properties d. Irreversible properties
Last Answer : Intensive properties
Description : What refers to the thermodynamic properties which are dependent on the amount of the substance present? a. Extensive property b. Intensive properties c. Reversible properties d. Irreversible properties
Last Answer : Extensive property
Description : The thermodynamic properties that are dependent on the size or extent of the system is called _____. A. Extensive property B. Intensive property C. Open property D. Closed property
Description : The thermodynamic properties that are independent on the size of the system is called _____. A. Extensive property B. Intensive property C. Open property D. Closed property
Last Answer : Intensive property
Description : How are thermodynamic properties classified? A. Physical and chemical B. Intensive and extensive C. Real and imaginary D. Homogeneous and heterogeneous
Last Answer : Intensive and extensive
Description : Write the effect of temperature on Equilibrium constant.
Last Answer : Ans. The value of Equilibrium constant changes with the temperature. The increase in rate depends upon activation energy .As the activation energy are different for forward & backward direction .So temperature will ... & backward direction. As K= Kf/ Kb ,so the state of equilibrium will be altered.
Description : Applying Le- Chatelier's principle, predict the effect of temperature and pressure on evaporation of water.
Last Answer : Ans Evaporation of water can be represented as water + heat water vapours: i) With increase in pressure- the equilibrium tend to shift in direction where there is decrease in the vol. i.e. ... left. ii) with increase in temperature- the equilibrium shifts to right as it is an endothermic reaction.
Description : What happens to the dissociation of PCl5 in a closed vessel if He gas is introduced into it at the same temperature?
Last Answer : Ans. No effect.
Description : Which measurable property become constant in Water Water vapors equilibrium at constant temperature
Last Answer : Ans. Vapour pressure.
Description : Two ideal gases under same pressure and temperature are allowed to mix in an isolated system. What will be the sign of entropy change?
Last Answer : Ans. Entropy change (∆S) is positive. It is because disorder or degree of freedom increases on mixing.
Description : Predict the entropy change in- (i) A liquid crystallizes into solid (ii) Temperature of a crystalline solid raised from 0K to 115K.
Last Answer : Ans. (i) Entropy decreases because molecules attain an ordered state. (ii) Entropy increases because from 0K to 115K average kinetic of moleculesincreases.
Description : Explain the effect of increasing the temperature of a liquid, on intermolecular forces operating between its particles. What will happen to the viscosity of a liquid if its temperature is increased? Arrange the following in increasing order of viscosity-water, hexane, glycerine.
Last Answer : Ans. On increasing the temperature , the kinetic energy of liquid molecules increases so that it can overcome the attractive forces between the molecules and hence liquid can flow more easily i.e. viscosity decreases. Order of increasing viscosity : hexane < water < glycerine.
Description : i)Vapour pressure increases with increase in temperature. ii)Giycerine is more viscous than water.
Last Answer : Ans. i) At higher temperature inter particle attraction weakens and more number of mole cules escape to vapour. ii) As interparticle forces are stronger in glycerine.
Description : What is the effect of temperature on surface tension and viscosity of a liquid?
Last Answer : Ans. Both decrease by increasing temperature.
Description : Why is the PH of blood remains almost constant?
Last Answer : Ans: Blood is a buffer solution and resist the change in PH
Description : How much is the percentage ionization of an electrolyte to classified is as 'weak electrolyte'?
Last Answer : Ans:
Description : What is the molarity of pure water?
Last Answer : Ans: 55.5M
Description : What type of substances are generally called 'electrolyte'?
Last Answer : Ans: Acid, bases and salts
Description : Why the Equilibrium constant is taken as dimensionless?
Last Answer : Ans. Activities are used in place of molar Conc. These represent the concentration or pressure with respect to standard state.
Description : Explain why the gas fizzes out when soda water bottle is opened?
Last Answer : Ans. In soda water bottle carbon dioxide gas is dissolved under pressure. As soon as the bottle is opened, the pressure inside the bottle tends to decrease, so the solubility decreases and gas escapes out.
Description : Write the significance of equilibrium constant?
Last Answer : Ans.The numerical value of equilibrium constant is a measure of the extent to which the reactants have been converted into products. A large value of K indicates large amount of ... its low value indicates less amount of reactants converted into products before achieving the equilibrium state.
Description : What are the conditions for getting maximum yield of NH3 by Haber’s process?
Last Answer : Ans. High conc. Of N2 &H2, Low Temp. & High Pressure.