Which mathematician has given the correct answer?

Question

I've been tasked at calculating the weight of 65,000 L of refrigerated liquid CO2 (UN Number 2187).

I've asked this question twice now and I've been given 2 different answers, which one is correct?

Here is answer one;
CO2 does not exist as a liquid at 1 atmosphere...
770 kg/m^3 (liquid at 56 atm and 20 °C)...
1 liter = 0.001 m^3...
65,000 liters = 65 m^3...
65 m^3 x 770 kg/m^3 = 50,050 kg = 50.05 metric tons


Here is answer 2;
Important information on environment, health and safety Safety Data Sheet
Carbon dioxide, refrigerated liquid.Molecular weight: 44 g/mol
UN number and proper shipping name UN 2187 Carbon dioxide, refrigerated, liquid
Relative density, liquid: 0,82
Melting point: -56,6 °C
Sublimation point: -78,5 °C
Critical temperature: 31 °C
Autoignition temperature: Not applicable.
Flammability range: Not applicable.
Relative density, gas: 1,52
Solubility mg/l water: 2000 mg/l
Density of liquid CO2 = 0.82 x 62.4lf/ft^3 = 51.168lb/ft^3 x 1 ft^3/28.317 liters = 1.807 pounds per liter
65,000 liters x 1.807 #/liter = 117,455 pounds = 53.277 tonnes

Can you assist in determining which answer is correct, perhaps both are incorrect?

Randy P · Accepted Answer

The second one seems to be from a specification of exactly what UN Number 2187 means, and you asked about UN Number 2187. So I would use that density of 0.82 rather than the first one, which used a density of 0.77 in the same units.

Both are right, but they're under different conditions. You need to know which conditions apply to your problem, and I'd say that the second one (UN Number 2187) seems to.

Which mathematician has given the correct answer?

1 Answer