Gibbs Free Energy & Spontaneity

Q. What is the relation between mole fraction and molality?

Q.

What is delta G in thermodynamics?

Q. Which of the following is correct? (1) The sum of mole fractions of all the components in a solution is always unity (2) Mole fraction depends upon temperature (3) Mole fraction is always negative (4) Mole fraction is independent of content of solute in solution

Q. what is Xa and Xb in relation between mole fraction and molality

Q.

In the conversion of limestone to lime:
$CaC{O}_3\left(s\right)\to CaO\left(s\right)+C{O}_2\left(g\right)$
The values of $△H^{\circ }$ and $△S^{\circ }$ are 179.1 kJ $mo{l}^{-1}$ and 160.2 J$K^{-1}$ respectively at 298 K and 1 bar. Assuming $△H^{\circ }$ and $△S^{\circ }$ remains constant with temperature, at which temperature conversion of limestone to lime will be spontaneous:

1. 845 K

2. 1118 K

3. 1008 K

4. 1200 K

Q.

In the evaporation of water, the entropy

1. increases

2. decreases

3. first increases and then decreases

4. does not change

Q.

ASSERTION(A): For every chemical reaction at equilibrium, standard Gibbs energy of the reaction is zero.
REASON(R): At constant temperature and pressure, chemical reactions are spontaneous in the direction of the decreasing Gibbs energy.

1. If both (A) and (R) are correct, and (R) is the correct explanation for (A)

2. If the both (A) and (R) are correct, but (R) is not the correct explanation for (A)

3. If (A) is correct, but (R) is incorrect

4. IF (A) is incorrect, but (R) is correct

Q. How many moles and how many atoms of each element are present in 0.6g of urea

Q.

What is the value of G, if the equilibrium constant for a reaction is 10.

Q. Three moles of an ideal gas expanded spontaneously into vacuum. The work done will be :

1. infinite
2. 3 Joules
3. 9 Joules
4. zero

Q.

The magnetic field of a solenoid can be made stronger by

1. increasing the number of turns

2. increasing the magnitude of current flowing through it

3. increasing the length of the solenoid

4. inserting a hard iron core

Q. Which of the following statements is correct for the spontaneous adsorption of a gas?

1. $\Delta S$ is negative and, therefore $\Delta H$ should be highly positive.
2. $\Delta S$ is negative and therefore, $\Delta H$ should be highly negative.
3. $\Delta S$ is positive and therefore, $\Delta H$ should be negative.
4. $\Delta S$ is positive and therefore, $\Delta H$ should also be highly positive.

Q. The correct thermodynamic conditions for the spontaneous reaction at all temperatures is

1. $\Delta H<0and\Delta S>0$
2. $\Delta H<0and\Delta S<0$
3. $\Delta H<0and\Delta S=0$
4. $\Delta H>0and\Delta S<0$

Q. The standard heat of combustion of solid boron is equal to

1. 

2. 

3. 

4. 

Q. The equilibrium constant for a reaction is 10. what will be value of $△G^{\ominus }$ ? R =8.314 $J{K}^{-1}mo{l}^{-1}$, T=300 K

Q. Which of the following relation(s) is/are correct?
Here,
$\Delta G=\text{Change in Gibbs' free energy}n=\text{no. of moles of electron transferred in a reaction}F=\text{Faraday constant}{E}_{cell}=\text{Cell potential or emf}$

1. $\Delta G=\text{Maximum useful work}$
2. $\Delta G=\text{Minimum useful work}$
3. All of the above
4. $-n\Delta G=F{E}_{cell}$

Q. Calculate the standard free energy change for the reaction,
$N_2\left(g\right)+3H_2\left(g\right)\to 2N{H}_3\left(g\right)at298K.$
Given $△H^o=-92.4kJmo{l}^{-1}$ and $△S^o=-198.3J{K}^{-1}mo{l}^{-1}$

1. -85.50 kJ/mol
2. 33.31 kJ/mol
3. -33.31 kJ/mol
4. 85.50 kJ/mol

Q.

$△H$ and $△S$ for the reaction: $A{g}_{2}O\left(s\right)\to 2Ag\left(s\right)+\frac{1}{2}{O}_2\left(g\right)$ are 30.56 kJ $mo{l}^{-1}$ and 66.0 J $K^{-1}mo{l}^{-1}$ respectively. Calculate the temperature at which free energy change for the reaction will be zero. Predict whether the forward reaction will be favored above or below this temperature.

1. 298 K, above

2. 300 K, below

3. 373 K, above

4. 463 K, above

Q. Why the sum of mole fractions of the components in solution ie equal to one (1)??

Q.

For $H_{2}O\left(l\right)(1bar,373K)$ being transformed to $H_{2}O\left(g\right)(1bar,373K)$, the correct set of thermodynamic parameters is:

1. $\Delta G=0$

2. $\Delta S=-ve$

3. $\Delta G=-ve$

4. $\Delta S=+ve$

Q.

Calculate the free energy change when 1 mol of NaCl is dissolved in water at 298 K. given:
(i) Lattice energy of NaCl = -778 kJ $mo{l}^{-1}$
(ii) Hydration energy of NaCl = -778 kJ $mo{l}^{-1}$
(iii) Entropy change at 298 K = 43 J $mo{l}^{-1}$

1. -9.11 kJ

2. -11.9 kJ

3. -10.9 kJ

4. None of these

Q. What is the free energy change $\left(△G\right)$ when 1.0 mole of water at ${100}^{o}C$ and 1 atmospheric pressure is converted into steam at ${100}^{o}C$ and 1 atmospheric pressure?

1. 80 cal
2. 540 cal
3. 620 cal
4. zero

Q. The following reaction is performed at 298K
$2NO\left(g\right)+O_2\left(g\right)\rightleftharpoons 2N{O}_2\left(g\right)$
The standard free energy of formation of NO(g) is 86.6kJ/mol at 298K. What is the standard free energy of formation of $N{O}_2\left(g\right)$ at 298 K? $K_p=1.6\times {10}^{12}$

1. $R\left(298\right)In(1.6\times {10}^{12})-86600$
2. $86600+R\left(298\right)In(1.6\times {10}^{12})$
3. $86600-\frac{In(1.6\times {10}^{12})}{R\left(298\right)}$
4. $0.5[2\times 86600-R(298\left)In\right(1.6\times {10}^{12}\left)\right]$

Q.

The $\Delta H$ and $\Delta S$ for a reaction at one atmospheric pressure are +30.558 kJ and 0.066 k J $k^{-1}$ respectively. The temperature at which the free energy change will be zero and below this temperature the nature of reaction would be:

1. 483 K, spontaneous

2. 443 K, non-spontaneous

3. 443 K, spontaneous

4. 463 K, non-spontaneous

Q. For a reaction at ${25}^{\circ }C$ enthalpy change $\left(\Delta H\right)$ and entropy change $\left(\Delta S\right)$ are $-11.7\times {10}^{3}Jmo{l}^{-1}$ and $-105Jmo{l}^{-1}{K}^{-1}$ respectively. The reaction is:

1. spontaneous
2. non-spontaneous
3. instantaneous
4. none of these

Q. A reaction occurs spontaneously if

1. $T△S<△H$ and both $△H,△S$ are $+ve$
2. $T△S<△H$ and $△H=+ve,△S=-ve$
3. $T△S>△H$ and both $△H,△S$ are $+ve$
4. $T△S=△H$ and both $△H,△S$ are $+ve$

Q. The combustion of sucrose is used by aerobic organisms to provide energy to life sustaining processes. If all the energy capture is done by electrical processes, (non P-V work) then calculate the maximum available energy which can be captured by the combustion of 34.2 gm of sucrose.
Given: $\Delta H_{combustion}\left(sucrose\right)=6000{\text{kJmol}}^{-1}$ $\Delta S_{combustion}=180\text{J/K mol}$ and the body temperature is 300 K.

1. 600 kJ
2. 594.6 kJ
3. 5.4 kJ
4. 605.4 kJ

Q. Calculate $△G^o$ for the following reaction at $298\text{K}$:
$CO\left(g\right)+\left(\frac{1}{2}\right)O_2\left(g\right)\to C{O}_2\left(g\right);△H^o=-282.84\text{kJ/mol}$
Given,
$S_{C{O}_2\left(g\right)}^o=213.8{\text{J K}}^{-1}{\text{mol}}^{-1},S_{CO\left(g\right)}^o=197.9{\text{J K}}^{-1}{\text{mol}}^{-1},S_{O_2}^o=205.0{\text{J K}}^{-1}{\text{mol}}^{-1}$

1. $+557J/mol$
2. $-557kJ/mol$
3. $+257kJ/mol$
4. $-257kJ/mol$

Q. The following reaction is performed at 298 K.
$2NO\left(g\right)+O_2\rightleftharpoons 2N{O}_2\left(g\right)$
The standard free energy of formation of NO(g) is 86.6 kJ/mol at 298 K. What is the standard free energy of formation of $N{O}_2\left(g\right)at298K?(K_p=1.6\times {10}^{12})$

1. $R\left(298\right)ln(1.6\times {10}^{12})-86600$
2. 86600 + R(298) ln(1.6 $\times {10}^{12}$)
3. 866600 - $\frac{ln(1.6\times {10}^{12})}{R\left(298\right)}$
4. $0.5[2\times 86600-R(298\left)ln\right(1.6\times {10}^{12}\left)\right]$

Q. Given: For ethylene oxide $\Delta H_f^{\circ }$ and $\Delta S^{\circ }$ are $-51{\text{kJ mol}}^{-1}$ and $243{\text{J mol}}^{-1}{\text{K}}^{-1}$ respectively and acetaldehyde, $\Delta H_f^{\circ }$ and $\Delta S^{\circ }$ are $-166{\text{kJ mol}}^{-1}$ and $266{\text{J mol}}^{-1}{\text{K}}^{-1}$ respectively, then select the correct statements :

1. $\Delta H^{\circ }$ per the reaction is $-115{\text{kJ mol}}^{-1}$
2. $\Delta S^{\circ }=0.023{\text{kJ mol}}^{-1}{\text{K}}^{-1}$
3. Reaction is thermodynamically favourable
4. Low temperature can favour formation of more product