Which of the following is the disadvantage of helium, which can be used as carrier gas in gas chromatography?

A GSM cellular telephone standard requires a minimum of 9 dB rejection of interfering signal levels of -23 dBm at 3 MHz from the carrier, -33 dBm at 1.6 MHz from the carrier, and -43 dBm at 0.6 MHz from the carrier, for a carrier level of -99 dBm. Determine the required local oscillator phase noise at 3 MHz carrier frequency offset.

A

-138 dBc/Hz

B

-128 dBc/Hz

C

-118 dBc/Hz

D

None of the mentioned

A 2.0 L flask holds 0.40 g of helium gas. If the helium is evacuated into a larger container while the temperature is held constant, what will the effect on the entropy of the helium be?

A

It will remain constant as the number of helium molecules does not change.

B

It will decrease as the gas will be more ordered in the larger flask.

C

It will decrease because the molecules will collide with the sides of the larger flask less often than they did in the smaller flask.

D

It will increase as the gas molecules will be more dispersed in the larger flask.

Which of the following is the disadvantage of hydrogen, which can be used as carrier gas in gas chromatography?

A

Dangerous to use

B

Expensive

C

Reduced sensitivity

D

High density

Which of the following is the disadvantage of nitrogen, which can be used as carrier gas in gas chromatography?

A

Dangerous to use

B

Expensive

C

Reduced sensitivity

D

High density

Near a natural gas deposits, we require to set up a gas turbine plant. Geologist inform engineers that helium gas is found in abundance here. Hence, engineers seek to use helium as working medium for the gas power plant. This turbine is a _________

A

Multi-shaft open cycle gas turbine

B

Single shaft open cycle gas turbine

C

Closed cycle gas turbine

D

Simple Open cycle Gas Turbine

In the question below, is given a statement followed by two conclusions numbered I and II. You have to assume everything in the statement to be true, then consider the two conclusions together and decide which of them logically follows beyond a reasonable doubt from the information given in the statement. Give answer: (A) If only conclusion I follows (B) If only conclusion II follows (C) If either I or II follows (D) If both I and II follow. STATEMENT: Sun consists of huge amount of Helium. Sun is a typical midsize star. CONCLUSION 1: Most midsize stars will have at least some Helium. CONCLUSION 2: Large stars have more helium as compared to smaller stars.

A

C

B

A

C

B

D

Statement: The ration Cp/Cv is more for helium gas than that for hydrogen gas. Reason: Atomic mass of helium is more than that of hydrogen.

A

Both statement and reason are true and the reason is the correct explanation of the statement

B

Both statement and reason are true but the reason is not a correct explanation of the statement

C

Statement it true but the reason is false

D

Both statement and reason are false

Helium in a piston/cylinder at 20°C, 100 kPa is brought to 400 K in a reversible polytropic process with exponent n = 1.25. Helium can be assumed to be an ideal gas with constant specific heat. Find the specific work.

A

-587.7 kJ/kg

B

-687.7 kJ/kg

C

-787.7 kJ/kg

D

-887.7 kJ/kg

নিচের কোনটি গ্যাস ক্রোমাটোগ্রাফিতে বাহক গ্যাস হিসেবে ব্যবহার করা হয় না? (Which one of following gases is not used as a carrier gas in gas chromatography?)

A

N2

B

H2

C

He

D

O2

Which of the following is not a feature of carrier gas used in gas chromatography?

A

It must be chemically inert

B

It should be suitable for the detector employed

C

It should not be completely pure

D

It should be cheap

Which of the following is the disadvantage of helium, which can be used as carrier gas in gas chromatography?

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