density of ammonia
 

:( :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 !!!

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

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!!