As shown in Table 15.2, the equilibrium constant
for the reaction...

Question

As shown in Table 15.2, the equilibrium constant
for the reaction N21g2 + 3 H21g2 Δ 2 NH31g2 is
Kp = 4.34 * 10-3 at 300 C. Pure NH3 is placed in a 1.00-L
flask and allowed to reach equilibrium at this temperature.
There are 1.05 g NH3 in the equilibrium mixture.
(b) What was the initial mass of ammonia placed
in the vessel?

Accepted Answer

Hey everyone. So today we're being asked to calculate the initial mass of hydrogen iodide that was placed in a 500 millim flask to decompose into hydrogen and iodine gas. So we're given a few quantities that we can use to start off. We're given the volume of the flask, which is 500 ml. Oops 500 ml were given the pressure, Which is 1.1 ATMs or atmospheres were also given the temperature in 250°C. So seeing as we need to find the mass, we can actually go ahead and utilize our ideal gas formula PV is equal to N. R. T, where P is pressure in a T. M's. V. Is volume and leaders and is the moles R as the gas constant and T. Is temperature in kelvin. Now, seeing that we need to find the mass, we can actually use the quantity end for molds to actually reconvert that. So recall that to find the number of moles in something, we will take its mass and divide it by its molar mass, which I will denote with two M's or actually I'll use one big M, not to be confused with polarity, but we'll divide the mass by the molar mass in order to find out how many moles of something we have. So let's plug that into our equation. So PV is equal to M the mass R. T divided by the molar mass and rearranging for the mass. We then get M is equal to P. V. M by R. T. There are a few other things we need to do. The volume is in milliliters. But we can convert this really easily because recall that uh, One leader is equal to 10 to the power of three ml, which means 500 ml Times 1/10 to the third Gives us 0.5 ml. And we can find the kelvin while we do the problem. So let's write this out. We have em is equal to 1.180 M A T. M Times 0. L. Oh, I messed up over here. This is supposed to be 0.5 L ml but it is times 0.5 liters. The molar mass of hydrogen iodide is 127. g per mole. All divided by 0. A. T. M. Leaders per mole kelvin. And finally to convert Centigrade Kelvin, We just add 273. Kelvin. So our moles will cancel out as well our leaders, atmospheres and kelvin And we'll be left with the final answer of 1.64 g of hydrogen iodide gas. So the initial mass of hydrogen iodide gas that was placed in the flask is 1.64 g. I hope this helps. And I look forward to seeing you in the next one

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