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.

Explanation:

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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:

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

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the volume of fluid displaced would equal the volume of the gas. use a gas syringe - this is a laboratory instrument that can be used to withdraw a certain volume of gas from a closed system or to measure the volume of gas from a chemical reaction.

b is the correct answer

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