A 0.1358g zinc metal reacts completely with Dil HCL to produce 52.20ml of H2(g) at 22.0 degrees Celsius. The hydrogen gas is collected over water at 22.0 degree Celsius and a barometric pressure of 755 mm Hg. The water vapor pressure at 22.0 degrees Celsius is 19.8 mm Hg and the height of water column in the gas collecting tube is 12.0 cm (the density of mercury is 13.6 g/ml)

Question

a. Write a balanced equation for the reaction of zinc metal with Dil HCl.
Zn(s)+2HCl(aq)-->ZnCl2(aq)+H2(g)

b. Calculate the number of moles hydrogen gas produced from the mass of Zn(s) given above.
0.1358g Zn (1 mole Zn) (1 mole H)
---------- -----------
65.39g Zn 1 mole Zn
= 0.002077 moles of Hydrogen

c. What is the partial pressure of hydrogen gas expressed in mm Hg? Hint: Apply Dalton's Law of Partial Pressure.
P atompsheric= P hydrogen gas + P water vapor + P height of water column
P= 755torr-19.8torr-120mmHg(1mmHg/13.6)
= 726mm Hg

d. Calculate the ideal gas constant, R, in units of L*atm/mol*K
PV=nRT
R=PV/nT
I can solve the problem but what do I plug in for 'P'? Is it 755?

Answer 1

No. According to your numbers it would be 726/760 atm.