3 moles of hydrogen occupy a volume of 67.20 L, at standard temperature and pressure (STP, 0 ˚C and 760 mmHg). What is the density of hydrogen at STP?

At a certain temperature the rate of this reaction is first order in hi with a rate constant of : 0.0632s2hig=h2g+i2g suppose a vessel contains hi at a concentration of 1.28m . calculate how long it takes for the concentration of hi to decrease to 17.0% of its initial value. you may assume no other reaction is important. round your answer to 2 significant digits.