density of ammonia

[Lorraine]

:cry:

Will someone please help me !!!

The lab is 25oC
The density of ammonia is 0.760 g litre ^-1 at STP

I have to calculate the density of ammonia at 25oC and 760 mmHg

I knwo I have to determine the volume that 1 litre at STP would have at 25oC and 760 mmHg
but I dont know how !!!

[RobJim]

Well, you need to keep the units constant. So, figure out what STP is in mmHg and degrees Celcius. That's the first step.

[lula]

If the density of ammonia at lab temp. of 25 deg C = 0.760 g litre -1 and the pressure applied = 0.760 mmHg

Boyle's law (At least I think it's Boyle's law! Could have gotten mixed up on this one) states that, at a constant temperature, the pressure of a fixed mass of gas multiplied by its volume is constant.

therefore,

760 mmHg x (vol at 760 mmHg) = 1000 mmHg x 760 cm3
volume at 760 mmHg = 1000 mmHg x 760 cm3 / 760 mmHg

= 1000cm3

At a constant pressure, the volume of a fixed mass of gas divided by the absolute temperature is also a constant

therefore,

volume at 0 degrees C / 0 deg C = volume at 25 degrees C / 25 deg C = 1000 cm3 /
25 deg c

volume at 0 deg C = 1000 cm3 x 25 deg C/ 25 deg C = 1000 cm3

I think your STP in degrees and mmHg is 25 deg C and 760 mmHg.

I am quite useless at chemistry so if anybody wants to correct this mess then please feel free!!