Can someone please answer the ones I got incorrect? Thank you

How many atoms or molecules are there in a mole of a substance?

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.

When using the ideal gas law constant 0.0821, what unit is used for volume? a) galloonb) ouncec) milliliterd) liter