Sometimes in lab we collect the gas formed by a chemical reaction over water. This makes it easy to isolate and measure the amount of gas produced. Suppose H2 the gas evolved by a certain chemical reaction taking place at 40°C is collected over water, using an apparatus something like that in the sketch, and the final volume of gas in the collection tube is measured to be 80ml .

Required:
Calculate the mass of H2 that is in the collection tube. Round your answer to significant digits. You can make any normal and reasonable assumption about the reaction conditions and the nature of the gases.

Answer :

sebassandin

Answer:

[tex]m_{H_2}=6.2x10^{-3}gH_2[/tex]

Explanation:

Hello,

In this case, for the mentioned scheme, we can assume hydrogen could be ideal at the given temperature and 1 atm of pressure since its molecules will not present significant interactions taking it to non-idealities. Moreover, when we collect a gas in water, 1 atm is a common pressure under normal conditions. In such a way, we can compute the moles of hydrogen gas by using the ideal gas equation:

[tex]n=\frac{PV}{RT}=\frac{1atm*80mL*\frac{1L}{1000mL} }{0.082\frac{atm*L}{mol*K}*(40+273)K} =3.1x10^{-3}molH_2[/tex]

Finally, we compute the mass by using hydrogen's atomic mass:

[tex]m_{H_2}=3.1x10^{-3}molH_2*\frac{2gH_2}{1molH_2}\\ \\m_{H_2}=6.2x10^{-3}gH_2[/tex]

Best regards.

Eduard22sly

The mass of H₂ that is present in the collection tube is 6.22×10¯³ g

We'll begin by calculating the number of mole of the H₂ in the tube. This can be obtained by using the ideal gas equation as illustrated below:

Temperature (T) = 40 °C = 40 + 273 = 313 K

Volume (V) = 80 mL = 80 / 1000 = 0.08 L

Pressure (P) = 1 atm

Gas constant (R) = 0.0821 atm.L/Kmol

Number of mole (n) =?

PV = nRT

1 × 0.08 = n × 0.0821 × 313

0.08 = n × 25.6973

Divide both side by 25.6973

n = 0.08 / 25.6973

n = 0.00311 mole

  • Finally, we shall determine the mass of the H₂ in the tube.

Mole of H₂ = 0.00311 mole

Molar mass of H₂ = 1 × 2 = 2 g/mol

Mass of H₂ =?

Mass = mole × molar mass

Mass of H₂ = 0.00311 × 2

Mass of H₂ = 6.22×10¯³ g

Thus, the mass of the H₂ in the tube is 6.22×10¯³ g

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