gases problem?

Question

2 HCOONa + H2SO4 => 2 CO + 2 H2O + Na2SO4
A 0.964 gram sample of a mixture of sodium formate [HCOONa] and sodium cholride is analyzed by adding sulfuric acid. The equation for the reaction for sodium formate with sulfuric acid is shown above. The carbon monoxide formed measures 242 mL when collected over water at 752 torr and 22.0°C. Calculate the percentage of sodium formate in the original mixture.

also... another quick question [btw, this is another problem]:

Volume of sample: 90.0 mL
Temp: 25°C
Atmospheric pressure: 745 mmHg
Equilibrium Vapor Pressure of H2O [25°C]: 23.8 mmHg

A. Calculate the number of moles of hydrogen gas collected.
B. Calculate # of molecules of water vapor in the sample.
C. Calculate the ratio of the average speed of the H molecules to the average speed of the water vapor molecules in the sample.
D. Which of the two gases, H2 or H2O, deviates more from ideal behavior? Explain your answer.

i did parts A and B, but C and D just lost me there.
thanks! :D

Answer 1

your first question is just a stoichiometry problem with gas laws thrown in. From the pressure, volume and temperature, you can calculated the number of moles of CO formed in the reaction. Then you can use stoichiometry to figure out how many moles of NaFormate you started with. With it's molecular weight, you can determine the mass of NaFormate in your sample, and then compare that with the starting mass.

For part D of the second one: THe ideal gas law assumes several things about the gas. For example, the molecules of a gas have no volume, that all collisions between molecules are perfectly elastic collisions, and the there is no interaction between the molecules of a gas. Gases like He pretty well follow the ideal gas law. Think about what you know about molecules of H2 and H2O. Think about the kinds of and strength of intermolecular forces of attraction between the molecules. THink, too, about the sizes of these two molecules. That should get you to the answer...