Description : From thermodynamic point to which system the animals and plants belong?
Last Answer : Ans. Open system.
Description : What is a thermodynamic state function?
Last Answer : Ans. A function whose value is independent of path. eg. P, V, E, H
Description : Entropy of the universe is - (1) continuously increasing (2) continuously decreasing (3) zero (4) constant
Last Answer : (1) continuously increasing Explanation: In an irreversible process, entropy always increases, so the change in entropy is positive. The total entropy of the universe is continually increasing.
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 : Is the bond energy of all the four C-H bonds in CH4 molecule equal? If not then why ? How is C-H bond energy then reported?
Last Answer : Ans. No because after breaking of C-H bonds one by one, the electronic environments change. The reported value is the average of of the bond dissociation energies of the four C-H bonds.
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 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 : (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 : Elaborate the statement that physical state of existence at given conditions is a balance between the thermal energy and intermolecular forces.
Last Answer : Ans. Intermolecular forces tend to keep the molecules together but thermal energy of the molecules tends to keep them apart. The three states of matter are the result of the balance between intermolecular forces and thermal energy of the molecules.
Description : Arrange solid, liquid and gas in order of energy. Give reason.
Last Answer : Ans. Solid < liquid < gas. This is because solid absorb energy to change into a liquid which further absorb energy to change into a gas.
Description : What do you mean by thermal energy?
Last Answer : Ans. Thermal energy is the energy of a body arising from motion of its atoms or molecules.
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 : Explain Hess’s law.
Last Answer : Ans. It states that the enthalpy change of the reaction remains the same whether the reaction is carried out in one step or several steps, i.e., ∆H = ∆H1 + ∆H2 + ∆H3 +…………
Description : When ΔH>0 and ΔS< 0, reaction is never spontaneous. Explain.
Last Answer : Ans. When ΔH > 0 , energy factor opposes the reaction . When ΔS< 0, i.e. randomness decreases, this factor also opposes the process. As both factors oppose the process, reaction is never spontaneous.
Description : Define the term system and surroundings. Explain the different types of system.
Last Answer : Ans. System : The part of the Universe which is under investigation. Surroundings: The remaining part of the Universe other than system. The system and surroundings are separated by well defined boundary. Types of system: (i) Open system (ii) Closed system (iii) Isolated system
Description : Out of NH3 and N2 which will have a) larger value of ‘a’ b)larger value of ‘ b’ .Explain.
Last Answer : Ans. a) NH3 will have larger value of a because of H – bonding. b) NH3 will have larger value of b due to larger molecular size.
Description : Explain how can gases be liquefied?
Last Answer : Ans. Gases can be liquefied by decrease of temperature and increase of pressure.
Description : Use the information and data given below to answer the questions Stronger intermolecular forces result in higher boiling point Strength of London forces increases with the number of electrons in the molecule ... here? (c) Why is the boiling point of HF highest while that of HCl lowest?
Last Answer : Ans :( a) In the molecules HCl, HBr and HI, dipole-dipole interaction and London forces are present. (b) Dipole moment of HCl > HBr > HI but boiling point of HCl < HBr
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 : On the basis of Boyle’s Law explain why mountaineers carry oxygen cylinder with them.
Last Answer : Ans. At high altitude as the atmospheric pressure is low , the air is less dense. As a result less oxygen is available for breathing .
Description : Is a thermodynamic system that operates continuously with only energy (heat and work) crossing its boundaries? a. Heat Engine b. Heat Reservoir c. Heat Source d. Heat Sink
Last Answer : Heat Engine
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 : 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 : 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 : 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 : 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 : 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.
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 : if the equilibrium constant for the reaction is 4.0, what will be the equilibrium constant for the reverse reaction.
Last Answer : Ans. Kc=1/4
Description : Which measurable property become constant in Water Water vapors equilibrium at constant temperature
Last Answer : Ans. Vapour pressure.
Description : what do you mean by homogenous and heterogeneous equilibrium?
Last Answer : Ans. Homogenous;-It is that equilibrium reaction in which all the reactants and the products are in the same phase. Heterogeneous equilibrium: - It is that equilibrium reaction in which all the reactants and the products are in two or more phases
Description : Write Application of Equilibrium constant?
Last Answer : Ans. (i) To predict the extent of the reaction. (ii) To predict the direction of the reaction. (iii) To calculate the equilibrium concentration.
Description : Write characteristics of Chemical equilibrium.
Last Answer : Ans. (i) At equilibrium the rate of forward reaction becomes equal to rate of backward reaction. (ii) A chemical equilibrium established only if none of the products are allowed to escape out ... can be attained from either direction. (iv) Catalyst does not alter the state of equilibrium.
Description : What will be the value of K ,If reaction is reversed?
Last Answer : Ans. The value of K will get inversed.
Description : what is Equilibrium?
Last Answer : Ans : Equilibrium represents the state of process in which properties such as temperature, pressure ,concentration of the system do not show any change with the passage of time. OR The state in which rate of forward reaction becomes equal to the rate of backward reaction.
Description : Water can be lifted into the water tanks at the top of the house with the help of a pump. Then why is not considered to be spontaneous?
Last Answer : Ans. A spontaneous process should continue taking place by itself after initiation . But this is not so in the given case because water will go up so long as the pump is working.
Description : What is the value of ∆G where ice and water are in equilibrium?
Last Answer : Ans. ∆G=0
Description : What is the sign of enthalpy of formation of highly stable compound?
Last Answer : Ans. Negative.
Description : Which have more entropy real crystal or ideal crystal and why?
Last Answer : Ans. Real crystal has more entropy because it has more disorderness.
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 : Predict the sign of ∆S for (a) the process of evaporation (b) the process of freezing.
Last Answer : Ans. (a) ∆S =+ve (b) ∆S=-ve
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 : 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 : 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.