Question

Zinc reacts with aqueous sulfuric acid to form hydrogen gas: Zn(s) + H2SO4(aq) → ZnSO4(aq) + H2(g) In an experiment, 225 mL of wet H2 is collected over water at 27 °C and a barometric pressure of 765torr. How many grams of Zn have been consumed? The vapor pressure of water at 27 °C is 26.74 torr.

Answer 1

we have for H2:

P = 765 torr - 26.74 torr

= 738.26 torr

= (738.26/760) atm

= 0.9714 atm

V = 225.0 mL

= (225.0/1000) L

= 0.225 L

T = 27.0 oC

= (27.0+273) K

= 300 K

find number of moles using:

P * V = n*R*T

0.9714 atm * 0.225 L = n * 0.08206 atm.L/mol.K * 300 K

n = 8.878*10^-3 mol

from reaction,

moles of Zn reacted = moles of H2 produced

= 8.878*10^-3 mol

Molar mass of Zn = 65.38 g/mol

we have below equation to be used:

mass of Zn,

m = number of mol * molar mass

= 8.878*10^-3 mol * 65.38 g/mol

= 0.580 g

Answer: 0.580 g