(8%) problem 9: helium is a very important element for both industrial and research applications. in its gas form it can be used for welding, and since it has a very low melting point (only 0.95 k under 2.5 mpa) it can be used in liquid form to cool superconducting magnets, such as those found in particle physics experiments. say we have a cylinder of n = 125 moles of helium gas at room temperature (t = 20° c). the cylinder has a radius of r = 17 cm and a height h = 1.64 m. what pressure is helium gas under?

2046.37 kPa

Explanation:

Given:

Number of moles, n = 125

Temperature, T = 20° C = 20 + 273 = 293 K

Radius of the cylinder, r = 17 cm = 0.17 m

Height of the cylinder, h = 1.64 m

thus,

volume of the cylinder, V = πr²h

= π × 0.17² × 1.64

= 0.148 m³

Now,

From the ideal gas law

we have

PV = nRT

here,

P is the pressure

R is the ideal gas constant = 8.314  J / mol. K

thus,

P × 0.148 = 125 × 8.314 × 293

or

P × 0.148 = 304500.25

or

P = 2046372.64 Pa = 2046.37 kPa

the arctic is a region of the planet, north of the arctic circle, and includes the arctic ocean, greenland, baffin island, other smaller northern islands, and the far northern parts of europe, russia (siberia), alaska and canada.

explanation:

v=uf/(u-f)

= 5.-10/(5+10) convex lens has negative focal length