Which gas law is applied in a fusible-plug pressure-relief valve?

(Answer to Q. 1)  ANS: D
The pressure-release valve allows some of the gas on top of the liquid to escape if the contents are warmed too much. This release of gas allows the gas within the container to expand, thus lowering the temperature. This maintains the gas under pressure between its boiling point and its critical temperature so that the majority of the reservoir's contents will be maintained in the liquid state.

(Answer to Q. 2)  ANS: A
Recall that in this system, indexing is accomplished by the exact placement of two pins into holes in the post valve.

(Answer to Q. 3)  ANS: D
Note that the connections for oxygen and other life-support gases are right-handed and external.

(Answer to Q. 4)  ANS: C
Solid carbon dioxide is used to refrigerate perishable materials during transport (e.g., food and laboratory specimens). Liquid carbon dioxide can be used as an expendable refrigerant and is used extensively as a fire-extinguishing agent in portable and stationary fire-extinguishing sys-tems.

(Answer to Q. 5)  ANS: B

(Answer to Q. 6)  ANS: B
Oxygen is an elemental gas that is colorless, odorless, and tasteless at normal temperatures and pressures. It makes up 20.9 of the Earth's atmosphere by volume and 23.2 by weight. It con-stitutes approximately 50 of the Earth's crust by weight. Oxygen is slightly heavier than air, having a density of 1.326kg/m3 at 21.1 C and 760 mm Hg (specific gravity = 1.105). At temper-atures less than 183 C (300 F), oxygen exists as a pale, bluish liquid that is slightly heavier than water.

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