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In 2 Na(s) + 2 H2O(l) 2 NaOH(aq) + H2(g), the hydrogen gas generated is collected over water at 25.0°C. The volume of the gas is 200 mL measured at 1.00 atm. What is the number of grams of sodium used? Vapor pressure of water at 25°C = 0.0313 atm.

1 Answer
Jun 24, 2018

Answer:

We need to assess the molar quantity of gas...we get approx. #400*mg# of sodium...

Explanation:

….for which we use the Ideal Gas equation...

#n_(H_2)=(PV)/(RT)=((1.00-0.0313)*atmxx0.200*L)/(0.0821*(L*atm)/(K*mol)xx298*K)=7.92xx10^-3*mol#...

We have SUBTRACTED #P_"saturated vapour pressure"# from the laboratory pressure....the gas is collected over water...

And we assess the reaction...

#Na(s) + H_2O(l) rarr 1/2H_2(g) + NaOH(aq)#

And thus there are 2 equiv of sodium metal...

#2xx7.92xx10^-3*molxx22.99*g*mol^-1=0.364*g#