Question

One 1.00-L flask (Flask A) contains NO gas, and another 1.00-L flask (Flask B) contains NO₂ gas, both at STP. Flask A contains:

1) less mass and fewer molecules than Flask B
2) less mass but the same number of molecules as Flask B
3) less mass but more molecules than Flask B
4) more mass and more molecules than Flask B

Answer 1

Flask A, with NO gas, has less mass but the same number of molecules as Flask B with NO₂ gas at STP, due to the lower molar mass of NO compared to NO₂.

Step-by-step explanation:

Regarding the question of whether Flask A, containing NO gas, has less or more mass and molecules than Flask B containing NO2 gas at STP, the answer lies in understanding the concepts of molar mass and Avogadro's hypothesis. Avogadro's hypothesis asserts that equal volumes of all gases at the same temperature and pressure contain the same number of molecules.

Since both flasks are of equal volume and at STP, this means they contain the same number of molecules of gas. However, the molar mass of NO is 30.01 g/mol, and the molar mass of NO2 is 46.01 g/mol. Consequently, even though both flasks have the same number of molecules, the mass of the gas in Flask B with NO2 is greater due to its higher molar mass.

Therefore, the correct option is: 2) less mass but the same number of molecules as Flask B.