How to Make Use of the Ideal Gas Law – Part 3

The ideal gas law, aka the general gas equation, is the equation of state of a hypothetical ideal gas.


It is a good approximation of the behavior of many gases under many conditions despite several limitations, and a combination of the empirical Boyle's law, Charles's law, Avogadro's law, and Gay-Lussac's law. The ideal gas law often takes an empirical form:

pV = nRT

where p, V, & T are the pressure, volume and temperature respectively; n is the number of moles; & R is the ideal gas constant.

Mnemonic: piVineRT = parainfluenza Virus ineRT

Question:

A 0.060 g piece of Magnesium was placed in Hydrochloric acid to generate Hydrogen according to the equation:

Mg(s) + 2HCl(aq) → MgCl2(aq) + H2(g)

The gas was collected at a pneumatic trough at 250C. A barometer reading of 755 mm Hg was made during the experiment. When the bubbles of Hydrogen ceased forming, the position of the bottle was adjusted so that the water level in the bottle was equal to that in the trough and the water level was marked on the bottle. Afterwards, 65 mL of water was needed to fill the bottle to the same mark. The vapor pressure of water at 250C is 23.8 mm Hg. How many moles of Hydrogen were produced?

Solution:



Click/tap to enlarge the image

p(gas) = p(atm) ─ p(water) as per Dalton’s law of partial pressures

(Aqueous) tension in the trough❓ Let Chemaficionado know in the comments below or at mychemistryhomework@gmail.com❗

References:

(1)    Ncert. Chemistry : Textbook for Class XI - Part.I; National Council Of Educational Research And Training: New Delhi.

(2)    Jespersen, N. D.; Barron's Educational Series, Inc. Barron’s AP Chemistry; Barron’s Educational Series: Hauppauge, N.Y., 2012.

‌(3)    Brown, C.; Ford, M. Higher Level Chemistry, 2nd ed.; Pearson Education: Harlow, Essex, 2014.

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