[helplessperson]

1.A mixture of HCl and SO2 gases occupies 4.36L at 0.983atm and 294K. The mixture is bubbled into pure water and dissolves compeltely to form a mixture of hydrochloric acid and dibasic acid H2SO3. The aqueous solution is titrated with 6.00M NaOH and a volume of 42.3mL is required to teach an endpoint. Find the number of moles of each gas in the original mixture.

For this question, the only information I found is that there were initially 0.178 mol of gases (HCl + SO2) and 0.254 mol of NaOH is required to neturalize the aqueous solution. I can't relate the amount of NaOH back to moles of HCL and SO2.


2.
A 5.0 L flask contains a mixture of ammonia gas (NH3) and diatomic nitrogen at 27°C and a total pressure of 3.00 atm. Gas is allowed to escape from the flask until the pressure inside falls to 1.00 atm, and the gas that escaped is passed through 1.50 L of 0.200 M acetic acid (CH3COOH). The ammonia from the gas mixture is entirely absorbed by the acid, and turns out to be just the right amount to neutralize the acid.
 
a) Write a balanced chemical equation for the reaction that occurs.
b) Assume that the liquid volume of 1.50 L remains constant during this process. Calculate the final concentrations of all species that are present in the aqueous solution in more than trace amounts. [NH4+] = [OAc-] = 0.200 M
c) Calculate the percentage by mass of ammonia in the original gas mixture.
 
The answers I got so for is
a. NH3 + HOAc → NH4+ + OAc-
b. [NH4+] = [OAc-] = 0.200 M
c. Not sure. I know that 0.300 mol of NH3 is bubbled through acid but can't find out how much NH3 was initially in the flask.

[Borek]

I can't relate the amount of NaOH back to moles of HCL and SO2.

Hint: you have n_HCl moles of HCl and n_SO2 moles of SO₂. What do you know about the total number of moles of the gas? What number of moles of NaOH is required to neutralize both n_HCl? n_SO2? Both together?

c. Not sure. I know that 0.300 mol of NH3 is bubbled through acid but can't find out how much NH3 was initially in the flask.

Think what change in pressure tells you about ratio of initial and left.

[helplessperson]

I can't relate the amount of NaOH back to moles of HCL and SO2.

Hint: you have n_HCl moles of HCl and n_SO2 moles of SO₂. What do you know about the total number of moles of the gas? What number of moles of NaOH is required to neutralize both n_HCl? n_SO2? Both together?

c. Not sure. I know that 0.300 mol of NH3 is bubbled through acid but can't find out how much NH3 was initially in the flask.

Think what change in pressure tells you about ratio of initial and left.

1. I know that nHCl + nSO2 = 0.178, so nSO2 = 0.178 - nHCl. 1 mol of HCl neutralizes 1 mol of NaOH. I also know that 1 mol of SO2 makes 1 mol of H2SO3, and 1 mol of 1H2SO3 requires 2 mol of NaOH to neutralize.

I set up the equation nHCl + 2(0.178 - nHCl) = 0.254 and got nHCl = 0.102 and nSO2 = 0.0760. Is this correct?

2. For the second question I still cant figure out for the life of me. I know that 2/3 of the total pressure escaped which means 2/3 of the total moles escaped too. A friend got 0.450 mol NH3 initially in the flask and the correct answer of 63.2% by mass, but I still don't understand how she got it (Her explanation wasn't very good).

[Borek]

1. I know that nHCl + nSO2 = 0.178, so nSO2 = 0.178 - nHCl. 1 mol of HCl neutralizes 1 mol of NaOH. I also know that 1 mol of SO2 makes 1 mol of H2SO3, and 1 mol of 1H2SO3 requires 2 mol of NaOH to neutralize.

I set up the equation nHCl + 2(0.178 - nHCl) = 0.254 and got nHCl = 0.102 and nSO2 = 0.0760. Is this correct?

Haven't checked the numbers but yes, setting up two equations (one in sum of moles, the other in sum of equivalents) is a correct approach here.

2. For the second question I still cant figure out for the life of me. I know that 2/3 of the total pressure escaped which means 2/3 of the total moles escaped too.

If 2/3 escaped, the amount left is what part of the initial amount?