A gas cylinder filled with nitrogen at STP has a mass of 37.289 g. The same cont

Question

A gas cylinder filled with nitrogen at STP has a mass of 37.289 g. The same container filled with carbon dioxide at STP has a mass of 37.440 g. When filled with an unknown gas at STP, the container mass is 37.062 g. Calculate the molecular weight of the unknown gas, and then state its probable identity. Find an MSDS for sodium hydroxide (NaOH) and print out. Write a short paragraph summarizing the key points of the MSDS and list any safety precautions that should be used when handling this material.

Explanation / Answer

1) At STP,

P=1atm

T=273.15K

V in both cases is same as same cylinder is filled.

PV=nRT (ideal gas equation)

V=n(N2)RT/P=n(CO2) RT/P=n(unknown)RT/P

or,n(N2)RT/P=n(CO2) RT/P=n(unknown)RT/P

or, m(N2)/M(N2)=m(CO2)/M(CO2)=n

m=mass

M=molar mass

or,37.289g/28.02g/mol=1.33 mol

37.440/44.01=0.85 mol

average value of n=1.33+0.85/2=1 mol

So n=1 mol=n(unknown)=mass/Molar mass=37.062g/M

or, 1mol=37.062g/M

or,M=37.062g/mol (near to the molar mass of argon=39)

2)

msds of NaOH

Keep in a tightly closed container free from moisture, heat . Always when making solution add caustic to water while stirring. Containers of NaOH are hazardous when empty as they may contain traces.Not to be stored with aluminum/ magnesium as it may react. Not to be mixed with acids or organic substances.

Health rating says its Severe (Poison) with no flammability.

Breathe in fresh air when inhaled.Large quantities of water to be taken when ingested.wash with plenty of water on skin contact .

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