Which volumes of gases at standard temperature and pressure have the same mass as 100 cm3 of O2?I.     50 cm3 of SO2II.     100 cm3 of CH4III.     100 cm3 of SiH4A.     I and II onlyB.     I and III onlyC.     II and III onlyD.     I, II and III

To answer this question, we need to understand the concept of molar volume. At standard temperature and pressure (STP), one mole of any gas occupies a volume of 22.4 liters, or 22400 cm3. This is known as the molar volume.

The molar mass of O2 is 32 g/mol. Therefore, the mass of 100 cm3 of O2 is (32 g/mol) * (100 cm3 / 22400 cm3/mol) = 0.143 g.

Now, let's calculate the mass of 100 cm3 of each of the other gases:

I. SO2: The molar mass of SO2 is 64 g/mol. Therefore, the mass of 50 cm3 of SO2 is (64 g/mol) * (50 cm3 / 22400 cm3/mol) = 0.143 g.

II. CH4: The molar mass of CH4 is 16 g/mol. Therefore, the mass of 100 cm3 of CH4 is (16 g/mol) * (100 cm3 / 22400 cm3/mol) = 0.071 g.

III. SiH4: The molar mass of SiH4 is 32 g/mol. Therefore, the mass of 100 cm3 of SiH4 is (32 g/mol) * (100 cm3 / 22400 cm3/mol) = 0.143 g.

So, the volumes of gases at standard temperature and pressure that have the same mass as 100 cm3 of O2 are 50 cm3 of SO2 and 100 cm3 of SiH4.

Therefore, the correct answer is B. I and III only.