When NH3 gas is introduced at one end of a long tube while HCl gas is introduced simultaneously at the other end, a ring of white ammonium chloride is observed to form in the tube after a few minutes. This ring is closer to the HCl end of the tube than the NH3 end. Why? I am completely confused as to why a ring forms and also why is is closer to the HCl end.
The ring forms because
NH3 + HCl ==> NH4Cl and NH4Cl is a white solid. It condenses (at least it aggregates) on the walls of the (glass?) tube. What do you know from the effusion/diffusion law (Graham's Law)?
The NH3 molecules and HCl molecules diffuse through the tube, moving toward each other. Which one moves faster? The smaller one, of course (the one with the lower mass). Which is the lower mass? NH3 has a molar mass of 17 and HCl is about 36.5. So HCl will move slower, NH3 will move faster, so the ring forms closer to the _______ end.
Thanks, that makes sense. But how can HCl and NH3 diffuse through a glass tube?
They don't. I think the problem states that NH3 is placed at the END of the tube and HCl is placed at the other END of the tube. It need not be glass but glass or plastic allows us to see where the white ring forms. Most of us don't have x-ray vision so a metal tube would make it difficult to demonstrate Graham's Law. Anyway, the vapors move through the tube from the ends and they meet, not in the middle but closer to the HCl end because the HCl vapors move slower than the NH3 vapors.
OK, I was just confused at your wording I think.
By the way, by measuring the distances traveled by the NH3 and HCl, we can calculate the ratio of the molar masses.
Which is the theoretical effusion of NH3?
and the the theoretical effusion of HCl?
no
yes
The theoretical effusion rate of a gas can be determined using Graham's Law of Effusion, which states that the rate of effusion of a gas is inversely proportional to the square root of its molar mass.
Using this law, we can calculate the effusion rates of NH3 and HCl.
The molar mass of NH3 is 17 g/mol, and the molar mass of HCl is 36.5 g/mol.
The effusion rate of NH3 would be the square root of the molar mass of HCl divided by the molar mass of NH3.
The effusion rate of HCl would be the square root of the molar mass of NH3 divided by the molar mass of HCl.
So, the theoretical effusion rate of NH3 would be the square root of 36.5 g/mol divided by 17 g/mol, and the theoretical effusion rate of HCl would be the square root of 17 g/mol divided by 36.5 g/mol.
Please note that these are theoretical values and may not exactly match the actual observations in the experiment.
The rate of effusion of a gas can be determined using Graham's Law of Effusion, which states that the rate of effusion of a gas is inversely proportional to the square root of its molar mass.
The formula for the rate of effusion is given as:
Rate of effusion = √(1/molar mass)
To calculate the theoretical effusion of NH3, we need to determine its molar mass, which is 17 g/mol. Plugging this value into the formula, we get:
Rate of effusion of NH3 = √(1/17)
Similarly, for HCl, whose molar mass is approximately 36.5 g/mol, the formula becomes:
Rate of effusion of HCl = √(1/36.5)
Simplifying these expressions will give you the numerical values for the theoretical effusion rates of NH3 and HCl.