35.0ml of hydrogen gas at STP weighs how many grams?

The at STP is ##"22.414L/mol"##. You must convert the given volume of hydrogen gas to liters. Then, using the molar volume, convert the liters to moles. Then convert the moles to mass using the molar mass of hydrogen gas, which is ##"2.016g/mol"##

Convert mL ##"H"_2## to liters.

##"35.0mL H"_2"## x ##"1 L"/"1000mL"## = ##"0.0350L H"_2##

Convert liters ##"H"_2## to moles.

##"0.0350L H"_2## x ##"1 mol H"_2/"22.414L H"_2## = ##"0.0015615mol H"_2##

Convert moles ##"H"_2## tp grams.

##"0.0015615mol H"_2## x ##"2.016g H"_2/"1 mol H"_2## = ##"0.00315g H"_2## (The final answer has three due to three significant figures in ##"35.0mL"##.)

At STP, ##"35.0mL"## of hydrogen gas has a mass of ##"0.00315g"##.