help with volumes and pressure?

Question

What volume (mL) of sulfur dioxide can be produced by the complete reaction of 3.82 g of calcium sulfite with excess HCl (aq), when the final SO2 pressure is 827 torr at 44.0 °C?

Answer 1

CaSO3(aq) + 2HCl(aq) ===> CaCl2(aq) + SO2(g) + H2O

Atomic weights: Ca=40 S=32 O=16 CaSO3=120

3.82gCaSO3 x 1molCaSO3/120gCaSO3 x 1molSO2/1molCaSO3 x 22,400mLSO2/1molSO2 x 760torr/827torr x 317K/273K =

The 3.82g CaSO3 is given. The next factor comes from the molecular weight. The g CaSO3 cancel, leaving moles CaSO3. The next factor comes from the balanced equation. The mols CaSO3 cancel, leaving mols SO2. The next factor comes from the molar volume of SO2 @ STP. The mols SO2 cancel, leaving mL SO2. The next factor comes from pressure higher than 760 torr needing a number < 1 to get the new volume. The next factor comes from the temperature higher than 273K needing a number > 1 to correct the volume.

Answer 2

First, predict the actual number of moles of SO2 that can be generated.
a. Need balanced reaction:
CaSO3 + 2HCl -----> SO2(g) + CaCl2(aq) + H2O(aq)
Note that all species other than SO2 are aqueous (and
have a charge) so they won't contribute to vapor pressure.
Therefore, all pressure present is attributed to SO2
Note also that charges balance; 0 = (2+) + (1-) + (1-)

b. That having been said, let's turn our attention to the Ideal
Gas Law: PV = nRT
We have, after the reaction takes place:
Ptot = PSO2 = 827 torr (= 827/760 = 1.09 atm)
V = ? (...that's what you're being asked to calculate)
n = # moles SO2 <--- we will get this from CaSO3 rx'd
R = 0.0821 lit-atm/mol-K
T = 44.0C + 273.15 = 317.15 K (must convert to K)

**All known now except V and n. Need n to get V.

c. Let's go after moles of SO2
moles CaSO3: 3.82g / 120.14 g/mole = 0.0318 moles
moles SO2 = 0.0318 moles (since 1:1 mole ratio in rxn)

d. Finally:

PV = nRT or
(1.09 atm)(V) = (0.0318 L)(0.0821 L-atm/mol-K)(317.2 K)

solve for V:
V = 0.7596 liters of SO2 or
V = 759.6 mL SO2 formed. (answer asked for in mL!!)

(ta da...)

Answer 3

Are you lazy to use some formulas...?