GATE XE topic:ideal-gas-mixtures PYQs & Answers

Questions 1–10 of 26. Imported answers require independent review unless marked reviewed.

Consider a mixture of ideal gases: nitrogen (N₂) and carbon-dioxide (CO₂), at 25 °C and 101 kPa. The molar mass of N₂ is 28 kg/kmol and the molar mass of CO₂ is 44 kg/kmol. If the molar mass of the mixture is 34 kg/kmol, which ONE of the following mixture compositions is possible?

Your answerChoose one option.

62.5% N₂ and 37.5% CO₂ by mass

62.5% N₂ and 37.5% CO₂ by volume

37.5% N₂ and 62.5% CO₂ by mass

37.5% N₂ and 62.5% CO₂ by volume

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A stream of moist air at 101 kPa and 25 °C undergoes a constant pressure process such that its dry bulb temperature increases and specific humidity decreases. For this process, which of the following statements is/are always CORRECT?

Your answerSelect all correct options. You can choose more than one.

Wet bulb temperature increases.

Dew point temperature decreases.

Relative humidity decreases.

Adiabatic saturation temperature increases.

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A stream of moist air enters an adiabatic saturator at 45 °C and 101 kPa and leaves as a saturated mixture at 30 °C. Make-up water to the saturator is supplied at 30 °C. The amount of make-up water (in grams per kg of dry air) supplied is __________ (rounded off to two decimal places).

Use the following data:

Specific heat capacity of water is 4.2 kJ/kg-K

Specific heat capacity of air at constant pressure is 1 kJ/kg-K

Saturated water properties:

At 30 °C: specific enthalpy of saturated water vapor is 2556 kJ/kg-K, specific enthalpy of saturated liquid water is 125.7 kJ/kg-K, and saturation pressure is 4.25 kPa

At 45 °C: specific enthalpy of saturated water vapor is 2582 kJ/kg-K, specific enthalpy of saturated liquid water is 188.4 kJ/kg-K, and saturation pressure is 9.60 kPa

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A rigid and impermeable tank has only moist air with a specific humidity of 0.025 kgwater-vapor/kgdry-air at 30 °C and 101 kPa. The air is heated to 90 °C. Assume moist air to behave as an ideal gas. The relative humidity (in %) of the heated air is ____________ (rounded off to two decimal places).

Saturation pressure of water at 30 °C is 4.25 kPa and at 90 °C is 70.18 kPa.

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A tank of 4 m

contains an ideal gas mixture of 60% hydrogen and 40% nitrogen by volume at 100 kPa and 300 K. Nitrogen is added to the tank such that the composition changes to 50% nitrogen by volume, with a final temperature of 300 K. The amount of nitrogen (in kmol) to be added is __________ (rounded off to three decimal places).

Use: Universal gas constant (Rᵤ) = 8.314 kJ/kmol-K

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A piston-cylinder arrangement contains an ideal gas mixture of 4 kg of hydrogen and 13 kg of nitrogen at 250 K and atmospheric pressure. On heat addition, the mixture expands at constant pressure until the temperature rises to 350 K. The average isobaric specific heats (

) for hydrogen and nitrogen are 14.239 kJ/kg-K and 1.040 kJ/kg-K, respectively. The amount of heat (in MJ) added to the cylinder is __________________ (rounded off to three decimal places).

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Air at 101 kPa, 15 °C and 50% relative humidity is first heated to 20 °C in a heating coil, and then humidified by spraying water on it. In the final state, the air has temperature of 25 °C and relative humidity of 85%. The amount of water sprayed (in gm per kg of dry air is _________________ (rounded off to two decimal places).

Use the following data:

The saturation pressure of water at 15 °C = 1.7057 kPa

The saturation pressure of water at 25 °C = 3.1698 kPa

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A rigid tank, initially at 1 bar and 300 K, contains 5 moles of

, 4 moles of

, and 3 moles of

. From this tank, 2 moles of

are removed keeping the temperature constant. Assuming ideal gas behavior, the final partial pressure of

(in bar) inside the tank is ________ (rounded off to three decimal places).

Use

J/mol.K

Molecular weights of

and

are 2 g/mol, 28 g/mol, and 32 g/mol respectively.

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100 moles of moist air at 70% relative humidity is cooled from 70 °C to 50 °C at a constant pressure of 1 bar. The vapour pressures of water are given in the table. The number of moles of water left in the moist air at the end of this process is ________ (rounded off to two decimal places).

Temperature (°C)	Vapour Pressure (kPa)
50	12.34
70	31.16

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A tank of volume V contains homogeneous mixture of two ideal gases, A and B at a temperature T and a pressure P. The mixture contains n_A moles of gas A and n_B moles of gas B. If P_A and P_B are the partial pressures of gas A and gas B, respectively, then

Your answerChoose one option.

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GATE XE topic:ideal-gas-mixtures PYQs

How to practice topic:ideal-gas-mixtures

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