# Chemical Forums

## Specialty Chemistry Forums => Chemical Engineering Forum => Topic started by: zeshkani_usa on January 16, 2013, 09:03:24 PM

Title: Quick question
Post by: zeshkani_usa on January 16, 2013, 09:03:24 PM
Hi there,

I have 1 question I have done it just wondering some feed back if this is right.

1.Calculate the Density of NaCl at 20C in [lbm/ft3]

here i used the Specific gravity of NaCl and which was 135lbm/ft3 multiply by 62.43lbm/ft3 which is the ref. for most soilds and liquids but this gives a very large density of 8370 lbm/ft3
but i was wondering if this could be done by using the V=nRT/P plug V into the D=M/V => D=m/(RT)
since there is no mention of the weight of NaCl i assumed 1mole
by doing this i get this answer 1.497022809933 lb/ft3 to get lbm/ft3 i just divied 1.49/32.2 =0.0357lbm/ft3
why is there such a difference between these 2 answers
is there a better method of doing this?

Title: Re: Quick question
Post by: sjb on January 17, 2013, 02:37:33 AM
Hi there,

I have 1 question I have done it just wondering some feed back if this is right.

1.Calculate the Density of NaCl at 20C in lbm/ft3

here i used the Specific gravity of NaCl and which was 135lbm/ft3 multiply by 62.43lbm/ft3 which is the ref. for most soilds and liquids but this gives a very large density of 8370 lbm/ft3
but i was wondering if this could be done by using the V=nRT/P plug V into the D=M/V => D=m/(RT)
since there is no mention of the weight of NaCl i assumed 1mole
by doing this i get this answer 1.497022809933 lb/ft3 to get lbm/ft3 i just divied 1.49/32.2 =0.0357lbm/ft3
why is there such a difference between these 2 answers
is there a better method of doing this?

What is the full name of the unit you are using? lbm/ft3? Check your units, what is the name of the formula you are using in the V=nRT/P strp?