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A 0.040 g piece of magnesium is placed in a beaker of hydrochloric acid. Hydrogen gas is generated according to the following equation:_______
Mg (s) + 2 HCl (aq) â MgCl2 (aq) + H2 (g)
The gas is collected over water at 25°C, and the gauge pressure during the experiment reads 784 mmHg.The gas displaces a volume of 100 mL. The vapor pressure of water at 25°C is approximately 24.0 mmHg. Based on this data, how many moles of hydrogen are produced in this reaction?
A. 4.04 Ã 10-5 moles hydrogen
B. 4.09 Ã 10-3 moles hydrogen
C. 3.07 Ã 10-2 moles hydrogen
D. 3.11 moles hydrogen

Respuesta :

Answer:

The correct answer is option B.

Explanation:

[tex]Mg (s) + 2 HCl (aq)\rightarrow  MgCl_2 (aq) + H_2 (g)[/tex]

Temperature of the hydrogen gas = T = 25°C=25+273 K= 298 K

Pressure of hydrogen gas ,P = gauge pressure - vapor pressure of water

[tex]P=784 mmHg-24 mmHg= 760 mmHg[/tex]

[tex]1 atm = 760 mmHg[/tex]

Volume of the hydrogen gas = V =100 mL =100 × 0.001 L= 0.1 L

(1 mL = 0.001 L)

Moles of hydrogen gas = n

[tex]PV=nRT[/tex] (ideal gas equation )

[tex]n=\frac{PV}{RT}=\frac{1 atm \times 0.1 L}{0.0821 atm l/mol K\times 298 K}[/tex]

n = [tex]4.09\times 10^{-3} moles[/tex]

[tex]4.09\times 10^{-3} [/tex]moles of hydrogen are produced in this reaction.

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