A sample of Nitrogen(N2)& Helium has a volume of 250mL @ 30degrees celsius & a total pressure of 745 mmHg a)If the pressure is 32mmHg what is the partial pressure of the Nitrogen? b) What is the volume of the Nitrogen at STP?
Partial pressures are additive. So, total pressure - partial pressure of Hg = partial pressure of nitrogen.
Use PV = nRT (using nitrogen's partial pressure) to find volume.
To solve these questions, we can apply the ideal gas law, which states that the product of pressure (P) and volume (V) is proportional to the number of moles (n) of a gas and the gas constant (R) at a given temperature (T). The equation is as follows:
PV = nRT
Let's break down the questions one by one:
a) If the total pressure is 745 mmHg, and we need to find the partial pressure of nitrogen (N2) when the pressure is reduced to 32 mmHg, we can use the concept of partial pressure. The partial pressure of a gas is the pressure it would exert if it occupied the entire volume on its own.
To calculate the partial pressure of nitrogen (N2), we need to know the mole fraction of nitrogen in the sample. The mole fraction (χ) can be calculated by dividing the moles of nitrogen by the total moles of all gases in the sample.
χ(N2) = n(N2) / n(total)
Since we are given the total pressure and volume, we can use the ideal gas law to find the initial number of moles of nitrogen (n(N2)):
(PV) / (RT) = n(N2)
Similarly, the mole fraction of helium (He) can be calculated using the mole fraction equation:
χ(He) = n(He) / n(total)
And the initial number of moles of helium (n(He)) can be found by rearranging the ideal gas law.
Once we know the mole fractions, we can calculate the partial pressure of nitrogen (P(N2)) by multiplying the mole fraction of nitrogen (χ(N2)) by the total pressure (P(total)):
P(N2) = χ(N2) * P(total)
b) To find the volume of nitrogen (N2) at STP (standard temperature and pressure), we need to convert the initial volume and temperature to the corresponding conditions at STP.
First, let's calculate the number of moles of nitrogen (n(N2)) using the ideal gas law:
(PV) / (RT) = n(N2)
Then, we can use the number of moles to find the volume of nitrogen at STP. At STP, 1 mole of any gas occupies 22.4 liters of volume. Therefore:
V(STP) = (n(N2)) * (22.4 L/mol)
Now, let's plug in the values into the equations and calculate the answers.