Indeal gas laws.?

Question

Some someone please explain how to do this problem and the answer to it. It would be greatly appreicated.

Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)

What is the volume, in liters, of H2 gas produced at 24°C and 835 mm Hg, from the reaction of 13.4 g Mg?

Answer 1

PV = nRT

T = 24ºC + 273 = 297 K
P = 835 mm Hg
n = 13.5 g * 24.305 g/mole Mg = 0.555 moles Mg
R = 62.3637 L• mmHg/K•mole
V = ?


V = nRT/P = 0.555*62.3637*297/835 = 12.31 L

There is a 1:1 relationship between Mg and H2 so the Volume of H2 is

12.31 L

Answer 2

One solves this problem in two steps.

First determine the number of moles of hydrogen produced, given the mass of magnesium used. According to the equation, 1 mole of magnesium will produce one mole of hydrogen gas, so just figure the number of moles of magnesium from the atomic weight:

13.4 g Mg / (24 g Mg/mole) = 0.54 moles (Mg or H2)

The second step is to apply the ideal gas equation:

(Pressure)(Volume) = (moles)("factor x")(temperature)

What is given is given is pressure and temperature; the number of moles has been calculated and the "x factor" is a constant.

BTW: Since most gas has almost the same density, an approximation of volume and number of moles can be used; 1 mole of any gas occupies a volume of 22 cubic liters. The answer to the problem above would then be something around 12 cubic liters of gas.

Answer 3

Moles Mg = moles H2 = 13.4/24.3

That equals n in the equation pV = nRT. You need V.

Convert p to Pascals, and T to kelvin, and you're away!