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Zinc metal reacts with excess hydrochloric acid to produce hydrogen gas according to the following equation:
Zn(s)+2HCl(aq)→ZnCl2(aq)+H2(g)
The product gas, H2, is collected over water at a temperature of 20 degrees C and a pressure of 750 mm Hg. If the wet H2 gas formed occupies a volume of 9.18 L, the number of grams of H2 formed is _____ g. The vapor pressure of water is 17.5mm Hg at 20 degrees C.

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Answer:

0.738 g

Explanation:

P1 = Initial pressure = 750 mm Hg - 17.5mm Hg = 732.5 mmHg/760 =0.964 atm

V1= initial volume = 9.18 L

T1 = Initial temperature = 20 degrees + 273 = 293 K

n =?

From PV =nRT

n= PV/RT

n = 0.964 * 9.18/0.082 * 293

n= 8.85/24

n = 0.369 moles

mass = 0.369 moles  * 2g/mol

mass= 0.738 g

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