Could someone help me with both of these problems please. Question 24 of 35 Gene

Question

Could someone help me with both of these problems please. Question 24 of 35 General Chemistry 4th Editiop University Science Books presented by Sapling Learning A 0.246 gram sample of a metal, M, reacts completely with sulfuric acid according to: A volume of 257 mL of hydrogen is collected over water; the water level in the collecting vessel is the same as the outside level. Atmospheric pressure is 756.0 Torr and the temperature is 25 ?. The vapor pressure of water at various temperatures can be found in this table. Calculate the molar mass of the metal. Number Incorrect g/ molDid you subtract the vapor pressure of water at 25 c from the pressure in the collecting vessel? O Previous Give Up & View Solution # Try Again O Next ?? Exit

Explanation / Answer

Image 1:

First, you need to get to the moles of H2 produced.

The vapor pressure of H2O at 25 oC = 23.8 torr (literature value)

Subtract the vapor pressure of H2O at 25 oC from the pressure of the gas

So, 756.0 torr - 23.8 torr
   = 732.2 torr
   = (732.2 / 760)
   = 0.963 atm

Now, use the ideal gas law to calculate moles of H2:
PV = n RT
0.963 atm (0.257 L) = n (0.0821 L atm mol-1 K-1) (298K)
n = 0.010 mol H2

Since the stoichiometry of the reaction is 1:1, you had in the sample 0.010 mol of metal M(s).

So, the molar mass of M = 0.246 g / (0.010 mol) = 24.6 g/mol

Image 2:

a.

Density = Mass / Volume
             = (2.25 g) / (1.45 L)
            = 1.55 g/L

b.

Gas equation:
PV = nRT
or, n / V = P / RT
or, n / V = (1.05 atm) / [ (0.08205746 L?atm K-1 ?mol-1) x (55 + 273) K) ]
or, n / V = (1.05 atm) / [ (0.08205746 L?atm K-1 ?mol-1) x (328) K) ]
or, n / V = 0.039 mol/L

Molar mass = (1.55 g/L) / (0.039 mol/L)
                   = 39.74 g/mol

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