A 0.464 gram sample of a metal, M, reacts completely with sulfuric acid according to:

Question

M(s) +H2SO4(aq)=MSO4(aq)+H2(g)
A volume of 211 mL of hydrogen is collected over water; the water level in the collecting vessel is the same as the outside level. Atmospheric pressure is 756.0 Torr and the temperature is 25°C. Calculate the atomic mass of the metal. Every time it's wrong. Please walk me through this

Answer 1

R=62.3637 L·Torr/mol·K
L=0.211L
P=756.0 Torr
T=273.15+25ºC

Use PV=nRT and solve for moles, n.

moles of H2=n=PV/RT

moles of H2=moles of M

You know that

moles of M=0.464g of M

and

1 mole of M=Atomic weight

(moles of M/0.464g of M)=(1 mole of M/Atomic weight)


solve for atomic weight,

atomic weight=0.464g of M/moles of M

Answer 2

I think there must be a correction for the vapor pressure of H2O at the temperature stated.
That would make that part
(756-23.8)(0.211)/[(62.364*298)]= 0.00831 mols. Then proceed to molar mass.

Answer 3

Okay, I think I see why.