How do you find the density of...?

Question

The question is "What is the density of NH3 (the three is little) at 800 (the last zero has a line over it) torr and 25 degrees C"

It doesn't matter if you answer it or not, but can someone just help me with the type of formula you would use in order to get this answer.

(or, if for some reason you know a page number i could find this on in "Prentice Hall Chemistry- The Physical Setting 2008", even though I know that it's really random, could you give me that)

Answer 1

v=volume

p=pressure

R=universal gas constant

T=temperature

pv=nRT

x= amount in grams

M= molecular mass

n=x/M

density=mass/volume

p=[(x/v)RT]/M

p=dRT/M

760torr=1.013bar

800torr=1.0663bar

p=1.0663bar

T=25+273

=298K

R=8.314 J mol^ -1 k^ -1

M=14+3

  =17g/mol

d=pM/RT

=(1.0663*17)/(8.314*298)

=3.0126*10^ -3

Answer 2

Use Ideal Gas Law ..

PV=mRT

P = Pressure = 800 torr (106.7 kPa)

V = Volume

m = mass

R = Ideal gas constant for ammonia = 0.4882 kJ/(kg*K)

T = Temperature = 25 deg C = 298 K

and density = m/V

so m/V = P/(RT)

you should get 0.733 kg/m^3

Answer 3

Ideal Gas Law with Density

The Ideal Gas Law is an equation of state for a gas, which describes the relationships among the four variables temperature (T), pressure (P), volume (V), and moles of gas (n). One modified form of the Ideal Gas equation is to involve the density (d) and molecular weight (M) instead of volume (V) and moles (n).

The mathematical form of the Ideal Gas Law is:

PV = nRT and n = m/MW and d = m/V

Where:

P - pressure

V - volume

n - number of moles

T - temperature

m - mass

d - density

MW - Molecular Weight

R - ideal gas constant. If the units of P, V, n and T are atm, L, mol and K, respectively, the value of R is 0.0821 L x atm/K x mol or 8.314 J/K x mol.

The density (d) of a gas is defined as

d = m / V

Answer 4

Those all look good, and the reason the last zero on the 800 has a bar over is is to show that it is a significant figure (exactly 800 as opposed to 780 rounded to the nearest 100) which means you have to take 3 sig. figs. into consideration when you write down your answer.  But in this case it doesn't matter because the temperature is only reported to 2 sig. figs. so your answer should be.