Calculate the mass of Sn(s) produced when 4,48 dm3 of hydrogen gas reacts completely at STP
Answers
A sample of pure zinc with a mass of 5.98 g is reacted with excess hydrochloric acid and the (dry) hydrogen gas is collected at 25.0 ˚C and 742 mm Hg. What volume of hydrogen gas would be produced?
Solution
This is a “single state” problem, so we can solve it using the ideal gas law, PV = nRT. In order to find the volume of hydrogen gas (V), we need to know the number of moles of hydrogen that will be produced by the reaction. Our stoichiometry is simply one mole of hydrogen per mole of zinc, so we need to know the number of moles of zinc that are present in 5.98 grams of zinc metal. The temperature is given in centigrade, so we need to convert into Kelvin, and we also need to convert mm Hg into atm.
Conversions:
25.0C+273=298K(9.6.1)
(742mmHg)×(1atm760mmHg)=0.976atm(9.6.2)
(5.98gZn)×(1.00mol65.39gZn)=0.0915mol(9.6.3)
Substituting:
PV=nRT(9.6.4)
(0.976atm)×V=(0.0915mol)(0.0821Latmmol−1K−1)(298K)(9.6.5)
V=(0.0915mol)(0.0821Latmmol−1K−1)(298K)(0.976atm)=2.29L(9.6.6)