Answer:- 13.6 L
Solution:- Volume of hydrogen gas at 58.7 Kpa is given as 23.5 L. It asks to calculate the volume of hydrogen gas at STP that is standard temperature and pressure. Since the problem does not talk about the original temperature so we would assume the constant temperature. So, it is Boyle's law.
Standard pressure is 1 atm that is 101.325 Kpa.
Boyle's law equation is:

From given information:-
= 58.7 Kpa
= 23.5 L
= 101.325 Kpa
= ?
Let's plug in the values and solve it for final volume.

On rearranging the equation for 

= 13.6 L
So, the volume of hydrogen gas at STP for the given information is 13.6 L.
Answer:
C.) The number after it is between 5 and 9
Explanation:
If the digit to the right is less than five, you must leave the digit you want to round to as it is.
But, if the digit to the right is greater than or equal to five, you must increase the value of the digit you're rounding to by one. And any remaining digits before the decimal point become zeros, and any that are after the decimal point are dropped.
Hope this helps you out! : )
Answer:
4.3043x10^24
Explanation:
Atoms(H) = (3.575 mol H2S/1)(2 mol H/1mol H2S)(6.02x10^23/1molH)
Simple stoicheometry problem. Sorry for taking so long, took Chem sophomore year, its been a while