What is the density of ammonia gas, nh3, at 31°c and 751 mmhg?

First, we will use the general gas formula to get the number of moles.

PV = nRT where:

P is the pressure of gas = 751 mmHg = 100125.096375 Pascal

V is the volume = 1 liter = 0.001 m^3

n is the number of moles we want to calculate

R is the gas constant = 8.314 J / (K. mol)

T is the temperature = 31 degrees celcius = 304.15 degree kelvin

Substitute in the above equation to get the number of moles as follows:

100125.096375 * 0.001 = n * 8.314 * 304.15

n = 0.039595 moles

Now, we will use the number of moles to get the mass as follows:

number of moles = mass / molar mass

mass = number of moles * molar mass

number of moles = 0.039595 moles

molar mass of ammonia (NH3) = 14 + 3 (1) = 17 grams

Substitute to get the mass as follows:

mass = 0.039595 * 17 = 0.673122 grams

Last step is to get the density as follows:

density = mass / volume

mass = 0.673122 grams

volume = 1 liter

density = 0.673122 / 1 = 0.673122 grams/liter = 0.000675 kg/L