Tag: chemistry

Questions Related to chemistry

If the density of a certain gas at $30^oC$ and $768 \ torr$ is $1.35 \ kg/{m}^{3}$, the density at STP would be:

chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. $1.48 \ kg/{m}^{3}$

  2. $1.58 \ kg/{m}^{3}$

  3. $1.25 \ kg/{m}^{3}$

  4. $1.4 \ kg/{m}^{3}$

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Correct Option: A
Explanation:
From Ideal gas law,

$PM = dRT$

$P _1 = 768\ torr$
$T _1 = 30^0\ C = 303\ K$
$d _1 = 1.35 kg/ m^3$

At STP, 
$T _2 = 273\ K$
$P _2 = 760\ torr$

$\dfrac{P _1}{P _2} = \dfrac{d _1T _1}{d _2T _2}$

$\dfrac{768}{760} = \dfrac{1.35\times 303}{d _2\times 273}$

$d _2 = 1.48 kg/m^3$

Hence, option A is correct.

$5$ moles of $SO _{2}$ and 5 moles of $O _{2}$ are allowed to react to form $SO _{3}$  in a closed vessel. At the equilibrium stage, $60\%$ $SO _{2}$ is used up. The total number of moles of $SO _{2}$, $O _{2}$ and $SO _{3}$ in the vessel now is

chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. $10.5$

  2. $10.0$

  3. $8.5$

  4. $3.9$

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Correct Option: B

For an isolated system, the wall/boundary separating the system from surrounding must be

chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. rigid

  2. impermeable

  3. adiabatic

  4. diathermal

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Correct Option: A,B,C

Assertion: Heat is not a state function

Reason: The change of heat depends upon the

path followed

chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. both A and R are true and R is the correct explanation of A.

  2. both A and R are true but R is not the correct explanation of A.

  3. A is true but R is false.

  4. both A and R are false.

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Correct Option: A
Explanation:

Heat is a path function. The change of heat depends upon the path followed

Which of the following statement(s) is/are incorrect?

chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. For a closed system at rest with no fields, the sum of $q+w$ has the same value for every process that goes from a given state 1 to a given state 2

  2. If a closed system at rest in the absence of external field undergoes an adiabatic process that has $w=0$, then the temperature of system must remain constant

  3. A change in state from state 1 to state 2 produces a greater increase in entropy of the sytem when carried out irreversible than when carried out reversibly

  4. The change in entropy of the system for an adiabatic process in a closed system must be zero

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Correct Option: B,C,D

A container of volume $1{m}^{3}$ is divided into two equal parts by a partition. One part has an ideal diatomic gas at $300K$ and the other part has vacuum. The whole system is isolated from the surrounding. When the partition is removed, the gas expands to occupy the whole volume. Its temperature will be:

chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. $300K$

  2. ${ 227.5 }^{ o }C$

  3. $455K$

  4. ${455}^{o}C$

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Correct Option: A

Select the correct statements.

chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. State of a system is assumed to be in internal equilibrium and the temperature and pressure are uniform throughout the system.

  2. Thermal drift in a system with time is more in Dewar flask than in insulated system.

  3. Thermal drift in a system with time is more in non-insulated system than in insulated system.

  4. Thermal drift in a system with time is more in insulated system than in non-insulated system.

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Correct Option: A,C
Which of the following is not a state function?
chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. Temperature

  2. Density

  3. Work

  4. Volume

  5. Pressure

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Correct Option: C
Explanation:

Temperature, density, volume and pressure are state functions.
They are intrinsic properties of the system. Their values  depend on initial and final state only and are independent of path followed.
On the other hand, work is a path function. It is not an state function. Its value depends on the path followed.

Select the conditions which represent the criteria for spontaneity of a process in a closed system, from the following given conditions:


Serial Number Conditions
1. ${ \left( dG \right)  } _{ P,T }>0$
2. ${ \left( \Delta S \right)  } _{ universe }>0$
3. ${ \left( dU \right)  } _{ S,V }>0$
4. ${ \left( dH \right)  } _{ S,P }<0$
5. ${ \left( dS \right)  } _{ u,V }<0$
6. ${ \left( dS \right)  } _{ H,P }>0\quad $

chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. 1 & 4

  2. 1 & 2

  3. 3 & 5 

  4. 4 & 6

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Correct Option: B

Which of the following factors is of no significance for roasting sulphide ores to the oxides and not subjecting the sulphide ores to carbon reduction directly?

chemistry chemical thermodynamics system and surroundings introduction to thermodynamics basics of thermodynamics

  1. Metal sulphides are thermodynamically more stable than $CS _2$

  2. $CO _2$ is thermodynamically more stable than $CS _2$

  3. Metal sulphides are less stable than the corresponding oxides

  4. $CO _2$ is more volatile than $CS _2$

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Correct Option: A
Explanation:

The reduction of metal sulfides by carbon reduction process is not spontaneous as the change in Gibb's free energy ($\triangle G$) for such a process is positive. 

The reduction of metal oxides by carbon reduction process is spontaneous as $\triangle G$ for such a process is negative.
Thus $CO _2$ is more stable than $CS _2$ and the metal sulfides are more stable than the corresponding oxides.
Hence, factor listed in $(3)$ is of no. significance.