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The first law of thermodynamics states that the net heat energy supplied to the system is equal to sum of change in internal energy of the system and work done by the system. Let d Q amount of heat be supplied to the system resulting in a change of internal energy by dU. If the work done by the system is dW then, according to first law of thermodynamics, dQ = dU + dW.

The process of transfer of heat from a cold body to a hot body by doing work on the system is called refrigeration.

– 40°C is the temperature at which the value in the Celcius scale is equal to that in the Fahrenheit scale.

The second law of thermodynamics decides, whether a given process allowed by first law, will, actually take place or not. For example,

1. Transfer of heat- According to the second law of thermodynamics, dS (entropy) ≥  0, i.e., the system cannot move towards the direction of decreasing entropy/probability. Hence, heat cannot flow by itself from a hotter body to a colder body.

2. Expansion of a gas- According to the second law of thermodynamics, dS  ≥ 0. As entropy cannot decrease, therefore the probability that all the molecules, on their own, go back into one half of the vessel is practically zero. Therefor, this process (of expansion of gas) is irreversible.

3. Diffusion of Gases- According to the second law of thermodynamics, dS ≥ 0. As entropy cannot decrease, therefore process of diffusion of gases is irreversible.

4. A refrigerator or a heat pump is also based on the second law of thermodynamics. Energy in the from of electric energy has to be supplied to enable it to pump heat from inside at lower temperature to the surroundings at higher temperature.

Cyclic process - ''A Cyclic process consists of a series of changes which return the system back to its initial state.

Non-cyclic process- " In a non-cyclic process, the series of changes involved do not return the system back to its initial state".

The efficiency of a heat engine can be increased by choosing the hot reservoir at very high temperature and cold reservoir at very low temperature.

Before refrigerator and AC were invented, cooling was done by using blocks of ice. When cooling machines were invented, their capacity was expressed in terms of the equivalent amount of ice melted in a day (24 hours). The same term is used even today. 

(Note : 1 tonne = 1000 kg = 2204.6 pounds, 1 ton (British) = 2240 pounds = 1016.046909 kg, 1 ton (US) = 2000 pounds = 907.184 kg.]

Basically, heat is supplied by the burning fuel causing increase in the internal energy of the food (system), and the system does some work on its surroundings. In the absence of any data about the components of food and their thermal and chemical properties, we cannot evaluate changes in internal energy and work done.

The total work done by the engine = (1000 J/cycle) (5000 cycles/min) (10 min) = 5 × 10⁷ J.

As the temperature of the earth increases due to absorption of solar radiation, water from rivers, lakes, oceans, etc. evaporates and rises to high altitude. Water vapour forms clouds as water molecules come together under appropriate conditions. Clouds are condensed water vapour and are of various type, names as cumulus clouds, nimbostratus clouds, stratus clouds and high-flying cirrus clouds.

First law of thermodynamics : The change in the internal energy of a system (∆U) is the difference between the heat supplied to the system (Q) and the work done by the system on its surroundings (W).

Mathematically, ∆ U = Q – W, which is the same as Q = ∆ U + W.

Notes : 

1. if Q is positive, it means heat is added to the system. If Q is negative, it means heat is given out by the system or removed from the system, 

2. If ∆U is positive, it means there is increase in the internal energy of the system. If ∆ U is negative, it means there is decrease in the internal energy of the system,

3. If W is positive, it means it is the work done by the system on its surroundings. Negative W means work is done on the system by the surroundings,

4. The first law of thermodynamics is largely due to Joule. It is essentially the law of conservation of energy applied to the systems that are not isolated, i.e., the systems that can exchange energy with the surroundings.

Thermodynamics was developed in 1850 by Rudolf Clausius (1822-88) German theoretical physicist, His ideas were developed in 1851 by William Thomson [Lord Kelvin] (1824-1907), British physicist and electrical engineer,

5. Q = ∆ U + W. Here, all quantities are expressed in the same units, e.g., cal or joule. If Q and A U are expressed in heat unit (cal, kcal) and W is expressed in mechanical unit (erg, joule) then the above equation takes the form Q = ∆ U + \(\frac{W}{J}\), where J is the mechanical equivalent of heat.]

(1) Heat and work are energy that "sit" in the system True

Reason : ΔU = q + w

according to 1^st law at thermodynamic change in inertial energy equal to the sum of heat and work.

(2) In a reversible adiabatic there is no heat transfer into or out at the system  True

Reason : For adiabatic process, q = 0 always there is no heat transfer take place

(3) During an isothermal process, the internal energy of an ideal gas depends only on the volume False

Reason : Ideal gases have no forces between its molecules, no energy is required to maintain a certain volume in ideal gases. so there is no change in internal energy of system.

In nut shell internal energy of an ideal gas only depends on Temperature it do not depends on the volume.

(4) Change of enthalpy equal to heat transfer for all process False

Reason : ΔH = q 

only at constant pressure not at constant volume temperature

(5) There is no heat transfer in a constant volume process for a system of an ideal gas  False

Reason :According to law of thermodynamies 

Δ U = q + w

Δ U = q - pdv

ΔU = q

( at constant volume Δ v = 0)

It means at constant volume, change and internal energy equal to heat transfer only on temperature.

Hence, the given statement is False

T = 33K 

N₂O₄ ⇌ 2NO₂ 

Initial concentration 100% 

Concentration dissociated 50% 

Concentration remaining at equilibrium 50% – 100%

K_eq = 100/50 = 2 

∆G° = -2.303 RT log K_eq 

∆G° = -2.303 x 8.31 x 33 x log 2 

∆G° = -190.18 J mol^-1

A procedure by which the initial state of a system changes to its final state is called a thermodynamic process. During the process/ there may be 

1. addition of heat to the system 

2. removal of heat from the system 

3. change in the temperature of the system 

4. change in the volume of the system 

5. change in the pressure of the system.