When solid mercury(I) carbonate, Hg2CO3, is added to
nitric acid, HNO3, a reaction occurs to give mercury(II)
nitrate, Hg1NO322, water, and two gases A and B:
Hg2CO31s2 + HNO31aq2¡
Hg1NO3221aq2 + H2O1l 2 + A1g2 + B1g2
(a) When the gases are placed in a 500.0-mL bulb at 20 °C,
the pressure is 258 mm Hg. How many moles of gas
are present?

Question

Accepted Answer

Hello everyone today. We have the following problem. The reaction of oxalic acid and potassium chlorate produces potassium carbonate, water, gas X and gas Y. Giving us the following equation or chemical reaction here. The gasses were collected and placed in a 1.5 liter vessel at degrees Celsius. The final pressure of the vessel is 552 hg or millimeters per mercury. We are being asked to calculate the total moles of gas that are present. So the first thing we want to do is we want to recall our ideal gas law and our ideal gas law says that our pressure times are volume. It's going to be equal to the number of moles that we have times of gas constant r times our temperature. And so the second thing I wanna do is you want to rearrange for n because N represents the number of moles. And so when we rearrange this, we get that in is equal to our pressure in terms of volume divided by r gas constant times our temperature. And so thirdly, we want to convert our temperature from Celsius to kelvin. Since that is what the gas law is in units of. So we're gonna take our temperature Which is 27°C and we're going to add 273.15 Kelvin. That's gonna give us 300.15 Kelvin, we are going to save this number for later. The fourth thing that we want to do is you want to solve for pressure. So you want to solve for our pressure And by salt for pressure we want to convert our pressure from units of mm HG two atmospheres. And so we have our pressure here and the question which was 552 mm of mercury. And to convert that to atmospheres, we're going to use the conversion factor that one atmospheres is equal to 760 of mercury. It's our mm of mercury will cancel out and we will be left with 0.7263 atmospheres. We're gonna save that number for later. Now that we have all of our necessary units and values, we can now move on to our final step which is solve four moles. And so we have our equation here from step two. We have the moles is equal to our pressure which we solved for to be 0.7263 atmospheres Times our volume, which in the question states that is 1.5 l And this is going to go all over our gas constant, which is 0.08206. They were going to have leaders times atmospheres and the numerator for the units and then moles times kelvin in the denominator. And we're gonna multiply by our temperature which is 300 Kelvin all of our units here, We'll cancel. I'll accept far moles and that will give us our total moles is equal to 0.0442 moles of gas as our final answer. Overall, I hope that has helped, and until next time.

Verified Solution

Key Concepts

Ideal Gas Law

Gas Pressure Units

Stoichiometry of Gas Reactions