Chemisty Questions..?

Question

I need help w/ these questions...

-If 10 liters of Nitrogen reacts w/ 4 liters of Hydrogen at te same temperature and pressure - what is the volume of Ammonia produced?

-A sample of helium effuses through a porous container 6.5 times faster than does an unknown gas X. What is the molar mass of the unknown gas?

-At a certain temperature and pressure, chlorine molecules have a velocity of .038 m/s. What is the velocity of sulfur dioxide molecules under the same conditions?


Know Im basically clueless on how to do these, so ANY help would be great

Answer 1

1.) Write out your reaction equation and balance it.
N2 + 3H2 -> 2NH3

Gases have the same number of moles/L when at the same temperature or pressure, so the volume is proportional to the # of moles. Since you need 3 times as much Hydrogen as you do Nitrogen, and you have less Hydrogen, it's the limiting reactant.

3 L of H2 forms 2 L of NH3, so we can use cross-multiplication to find the volume of NH3:
3 L H2 / 2 L NH3 = 4 L H2 / x L NH3
x = 4 * 2 / 3 = 2.6667 L NH3.

2.) Graham's law: Effusion Rate 1 / Effusion Rate 2 = √(m2 / m1)
where m = molar mass of gas
We'll use Helium for 1, and gas X for 2, so that Rate 1 / Rate 2 = the 6.5 that we were given.

6.5 = √(m2 / m1)
6.5 = √m2 / √m1
6.5 √m1 = √m2
6.5 √4 = √m2
13 = √m2
169g/mol = m2

3.) 2 gases at the same temperature and pressure have the same kinetic energy.
E = 1/2 mv^2

Since the energy is equal, assume 1 mole of each gas to determine m. 1 will be chlorine, 2 will be SO2.
1/2 m1v1^2 = 1/2 m2v2^2
m1v1^2 = m2v2^2 (the 1/2 cancels)

m1 = Cl2 = 35.5 g/mol * 2 = 71 g
m2 = SO2 = 32 + 2 * 16 = 64 g/mol
71 * .038^2 = 64 * v2^2
v2^2 = 71 * .038^2 / 64 = 0.0016019375
v2 = 0.040 m/s (solution!)