# Test: Thermodynamics Level - 1

## 25 Questions MCQ Test Mechanical Engineering SSC JE (Technical) | Test: Thermodynamics Level - 1

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Attempt Test: Thermodynamics Level - 1 | 25 questions in 50 minutes | Mock test for Mechanical Engineering preparation | Free important questions MCQ to study Mechanical Engineering SSC JE (Technical) for Mechanical Engineering Exam | Download free PDF with solutions
QUESTION: 1

### The unit of power in S.I. units is

Solution:

Power is measured in Watts.

QUESTION: 2

### Work done in a free expansion process is

Solution:

During free expansion, no work is done by the gas. The gas goes through states of no thermodynamic equilibrium before reaching its final state, which implies that one cannot define thermodynamic parameters as values of the gas as a whole. So work done in a free expansion process is Zero.

QUESTION: 3

### An open system is one in which

Solution:

An open system is a system that freely exchanges energy and matter with its surroundings.

QUESTION: 4

Which of the following variables controls the physical properties of a perfect gas

Solution:

Perfect gas, also called ideal gas, a gas that conforms, in physical behaviour, to a particular, idealized relation between pressure, volume, and temperature called the general gas law. This law is a generalization containing both Boyle’s law and Charles’s law as special cases and states that for a specified quantity of gas, the product of the volume v and pressure p is proportional to the absolute temperature t; i.e., in equation form, pv = kt, in which k is a constant. Such a relation for a substance is called its equation of state and is sufficient to describe its gross behaviour.

QUESTION: 5

Which of the following laws is applicable for the behaviour of a perfect gas

Solution:

Boyle's Law

a law stating that the pressure of a given mass of an ideal gas is inversely proportional to its volume at a constant temperature.

Charle's Law

a law stating that the volume of an ideal gas at constant pressure is directly proportional to the absolute temperature.

Gay-Lussac's Law

law states that the pressure of a given mass of gas varies directly with the absolute temperature of the gas, when the volume is kept constant.

QUESTION: 6

According to kinetic theory of gases, the absolute zero temperature is attained when

Solution:

The average kinetic energy of gas molecules is directly proportional to absolute temperature only; this implies that all molecular motion ceases if the temperature is reduced to absolute zero.

QUESTION: 7

According to Gay-Lussac law for a perfect gas, the absolute pressure of given mass varies directly as

Solution:

Gay-Lussac's Law

Tlaw states that the pressure of a given mass of gas varies directly with the absolute temperature of the gas, when the volume is kept constant.

QUESTION: 8

Gas laws are applicable to

Solution:

Because density of gas and vapour are diferent

QUESTION: 9

According to Dalton's law the total pressure of the mixture of gases is equal to

Solution:

Dalton's law (also called Dalton's law of partial pressures) states that in a mixture of non-reacting gases, the total pressure exerted is equal to the sum of the partial pressures of the individual gases.

QUESTION: 10

A closed system is one in which

Solution:

In nonrelativistic classical mechanics, a closed system is a physical system that doesn't exchange any matter with its surroundings, and isn't subject to any net force whose source is external to the system. A closed system in classical mechanics would be considered an isolated system in thermodynamics.

QUESTION: 11

Superheated vapour behaves

Solution:
QUESTION: 12

The value of n = 1 in the polytropic process indicates it to be

Solution:

PVγ = constant

is the expression for Polytropic Process where γ is a constant

If γ = 1, PV = constant which is only true for an isothermal process.

Hence option C is correct.

QUESTION: 13

A piston cylinder contains 0.5 kg of air at 500 kPa and 500 K. The air expands in a process so pressure is linearly decreasing with volume to a final state of 100 kPa and 300 K. Find the work in the process.

Solution:

QUESTION: 14

Gases have

Solution:

The specific heats of gases are given as Cp and Cv at constant pressure and constant volume respectively while solids and liquids are having only single value for specific heat.

QUESTION: 15

Solution:

Avogadro's law states that, "equal volumes of all gases, at the same temperature and pressure, have the same number of molecules." For a given mass of an ideal gas, the volume and amount (moles) of the gas are directly proportional if the temperature and pressure are constant.

QUESTION: 16

The pressure of a gas in terms of its mean kinetic energy per unit volume E is equal to

Solution:

Pressure in terms of kinetic energy per unit volume:- The pressure of a gas is equal to two-third of kinetic energy per unit volume of the gas.

P = 2E/3

QUESTION: 17

Kinetic energy of the molecules in terms of absolute temperature (T) is proportional to

Solution:

Kinetic energy of molecules is the form of internal energy in a closed vessel, and internal energy is the function of temperature so kinetic energy of molecules is proportional to absolute temprature

QUESTION: 18

One kg of carbon monoxide requires __________ kg of oxygen to produce 11/7 kg of carbon dioxide gas.

Solution:

2CO + O2 = 2 CO2
(2*28) (16*2) (2*44)

=56 kg =32 kg =88 kg

=1 kg =32/56 kg =88/56 kg

=1 kg =4/7 kg =11/7 kg

That is 4/7 kg of O2 is required for preaparing 11/7 kg of CO2 from 1 kg CO.

QUESTION: 19

Absolute zero pressure will occur

Solution:

The absolute zero pressure will be when the molecular momentum of the system becomes zero. ... Thus, Pressure P = F/A = Rate of change of momentum/Area. Now when the ''rate of change of momentum' is zero, the above equation becomes: P = 0 / area = 0 which is the absolute zero pressure.

QUESTION: 20

No liquid can exist as liquid at

Solution:

Liquids are volatile. If taken to zero pressure which effectively means vacuum, in that case, it will boil and vapourise. While different liquids have different viscosity but eventually it will vapourise as there is no pressure to help it maintain the viscosity and surface tension. Water will vapourise much faster than say mercury.

QUESTION: 21

The condition of perfect vacuum, i.e., absolute zero pressure can be attained at

Solution:

The condition of perfect vacuum, i.e., absolute zero pressure can be attained at. a temperature of - 273.16°C. a temperature of 0°C.

QUESTION: 22

Specific heat of air at constant pressure is equal to

Solution:

For ordinary calculations - a value of specific heat cp = 1.0 kJ/kg K (equal to kJ/kg oC) or 0.24 Btu(IT)/lb °F - is normally accurate enough

QUESTION: 23

Characteristic gas constant of a gas is equal to

Solution:

We know by the formula Cp - Cv = R

QUESTION: 24

The behaviour of gases can be fully determined by

Solution:

Avogadro's Law states that equal volumes of all ideal gases (at the same temperature and pressure) contain the same number of molecules.

Boyle's Law states that equal pressure is inversely proportional to volume (when temperature is constant).

Charles's Law states that volume is proportional to temperature (when pressure is constant). Remember that temperature must be measured in Kelvin.

Gay-Lussac's Law states that pressure is proportional to temperature (when volume is constant).

QUESTION: 25

To convert volumetric analysis to gravimetric analysis, the relative volume of each constituent of the flue gases is

Solution:

To convert volumetric analysis to gravitational analysis, relative volume of each constituent of flue gases is multiplied by its molecular weight.

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