Spontaneity

Q.

How is Gibbs free energy related to enthalpy and entropy?

Q.

For an isolated system, $\Delta U=0$, what will be $\Delta S$?

Q.

How does temperature affect Gibbss free energy?

Q.

What is the SI unit of entropy?

Q.

For an exothermic chemical process occurring in two steps as (i) A+B→X (Slow) and (ii) X→AB (Fast). The progress of the reaction can be best described by:

1. 

2. 

3. 

Q.

According to Avogadro's Law, "Equal volumes of gases at the same temperature and pressure contain equal numbers of molecules". But how is this statement correct? How do we know that equal number of molecules are present in two gases taken in equal volumes?

Even if we consider equal volumes of any two gases(let's consider two gases for example) contain equal number of molecules, if we have the two gases in two containers of same volumes, we can add more gas to any one container and increase the density of the gas inside the container. In that case, the volume of the gas remains equal to the volume of the container but the number of gas molecules inside the container has increased and there is no chage to the number of molecules of the other gas we took inside a similar container. So now we have equal volumes of two gases but we have increased the number of molecules of one gas so now how can we say that the equal volumes of these two gases contain equal number of molecules?

If we take equal number of molecules of two gases and contain one of the gas in a container of some volume and the other gas in a container of a different volume, we will have unequal volumes of two gases having equal number of particles.

So how is Avogadro's Law explained?

Q.

For the reaction,
$2C{l}_{\left(g\right)}\to C{l}_{2\left(g\right)}$, what are the signs of $\Delta H$ and $\Delta S$ ?

Q. Which of following is a non spontaneous process?

1. Rusting of iron
2. Boiling of water
3. Diffusion
4. Melting of ice

Q.

Why is negative free energy spontaneous?

Q.

Calculate the amount of carbon dioxide that could be produced when
2 moles of carbon are burnt in 16g of dioxygen.

Q. Identify the correct statements regarding entropy

1. At $0^{o}C,$ the entropy of a perfectly crystalline substance is taken to be zero
2. At absolute zero of temperature, the entropy of all perfectly crystalline substance is positive
3. At absolute zero of temperature, the entropy of all crystalline substance is taken to be negative
4. At absolute zero of temperature, the entropy of a perfectly crystalline substance is taken to be zero

Q. Which one of the following has $△S^o$ greater than zero ?

1. $CaO\left(s\right)+C{O}_2\left(g\right)\rightleftharpoons CaC{O}_3\left(s\right)$
2. $NaCl\left(aq\right)\rightleftharpoons NaCl\left(s\right)$
3. $NaN{O}_3\left(s\right)\rightleftharpoons N{a}^{+}\left(aq\right)+N{O}_3^{-}\left(aq\right)$
4. $N_2\left(g\right)+3H_2\left(g\right)\rightleftharpoons 2N{H}_3\left(g\right)$

Q. Given are two statements one is labelled as Assertion A and other is labelled as Reason R.
Assertion A : Magnesium can reduce $A{l}_2{O}_3$ at a temperature below ${1350}^{\circ }C$, while above ${1350}^{\circ }C$ aluminium can reduce $MgO$.

Reason R : The melting and boiling points of magnesium are lower than those of aluminium.

In light of the above statements, choose most appropriate answer from the options given below :

1. A is correct R is not correct.
2. Both A and R are correct, but R is NOT the correct explanation of A.
3. A is not correct, R is correct.
4. Both A and R are correct, and R is correct explanation of A.

Q. Which of the following processes is spontaneous?

1. Boiling of water
2. All of these
3. Evaporation of water at room temperature
4. Flow of heat from a colder to a hotter body

Q. A certain reaction is non-spontaneous at 298 K. The entropy change during the reaction is 121 J/K. What is the minimum value of
$△H$ (in $kJ$) for the reaction.

Q.

How can we calculate delta G of a reaction?

Q.

Does a process that violates the second law of thermodynamics violate the first law of thermodynamics$?$

1. True
2. False

Q. Limitations of first law of thermodynamics in simple and easy to understand words

Q.

What is the value of $∆\mathrm{G}$ when a system is at equilibrium?

Q.

Are all reactions reversible?

Q. Which of the following processes is spontaneous?

1. Flow of heat from a colder to a hotter body
2. Boiling of water
3. Evaporation of water at room temperature
4. All of these

Q. The correct thermodynamic conditions for the spontaneous reaction at all temperatures is : (a) ∆H<0 and ∆S < 0 (b) ∆H < 0 and ∆S <0 (c) ∆H <0 and ∆S = 0 (d) ∆H >0 and ∆S < 0 Reaction is spontaneous when ∆S is positive and ∆H is negative

Q. The ratio of rates of diffusion of two gases is 6:4. Calculate the ratio of their Molecular Weights.

1. 4:9
2. 8:3
3. 9:4
4. 6:4

Q.

Catalyst only

1. Decreases activation energy

2. increases activation energy

3. None of these

4. Brings about equilibrium

Q.

The spontaneity means, having the potential to proceed without the assistance of external agency. The processes which occur spontaneously are
(a) flow of heat from colder to warmer body
(b) gas in a container contracting into one corner
(c) gas expanding to fill the available volume
(d) burning carbon in oxygen to give carbon dioxide

Q. The total entropy change $\left(△S_{total}\right)$ for the system and the surrounding of a spontaneous process is given by:

1. $△S_{surr}=△S_{total}-△S_{system}<0$
2. $△S_{system}=△S_{total}+△S_{surr}>0$
3. $△S_{total}=△S_{system}+△S_{surr}>0$
4. $△S_{total}=△S_{system}-△S_{surr}>0$

Q. When disorderness of a system increases, the change is said to be:

1. Exothermic
2. Non-spontaneous
3. Endothermic
4. Spontaneous

Q. The signs of $\Delta$H, $\Delta$S and $\Delta$G for a non-spontaneous reaction at all temperatures would be:

1. +, +, -
2. +, -, +
3. -, -, -
4. +, +, +

Q.

Which of the following reaction(s) can be spontaneous?

1. $H_2\left(g\right)+\frac{1}{2}{O}_2\left(g\right)\to H_{2}O\left(l\right)$; $△$ H = -285.7 kJ/mol

2. $H_{2}O\left(l\right)\to H_{2}O\left(g\right)$; $△$ H = +44 kJ/mol

3. All of these

4. $N{H}_{4}Cl\left(s\right)\to N{H}_4^{\oplus }\left(aq\right)+C{l}^{\ominus }\left(aq\right)$; $△$ H = +15.1 kJ/mol

Q.

How do I calculate $∆\mathrm{G}$?