25. Hydrogen is produced by the complete reaction of 6.24 g of sodium with an excess of gaseous hydrogen chloride.Previous Chapter
(a) Write a balanced chemical equation for the reaction that occurs.2Na(s) + 2HCl(g) ---> H2(g) + 2NaCl(s)(b) How many liters of hydrogen will be produced at a temperature of 50.0 C and a pressure of 0.850 atm?We find the amount of sodium atoms in the given substance by using stoichiometry. We divide the mass of sodium by its gram formula weight.41. (a) Compute the root-mean-square speed of H2 molecules in hydrogen at a temperature of 300 K.
mol Na = 6.24 g / 22.99 g mol -1
= 0.2714 mol
We then multiply the amount of known mol by the coefficient ratio of the known over the unknown.
mol H2 = 0.2714 x (1/2)
= 0.1357 mol
We then use the combined gas law to calculate the volume of hydrogen gas that is produced during the reaction.
PV = nRT
V = nRT
P
= (0.1357 mol) x (0.0820578 L atm/mol K) x (323.15 K)
0.850 atm
= 4.225 LTo find the roo-mean-square speed of the hydrogen molecules we must first convert hydrogen's gram formula weight from g/mol to kg/mol.(b) Repeat for SF6 molecules in gaseous sulfur hexafluoride at 300 K.2.0158 g/mol = 2.0158 x 10-3 kg/mol
We can now find the root-mean-squared speed.
Urms = (3RT/M)1/2
= [3(8.3145 kg m2 / s2 mol K)(300K)]1/2
2.0158 x 10-3 kg/mol
= 1862 m/sAgain, we must first convert the gram formula weight of the molecule from g/mol to kg/mol.164 g/mol = .164 kg/mol
Now we can calculate the root-mean-square.
Urms = (3RT/M)1/2
= [3(8.3145 kg m2 / s2 mol K)(300 K)]1/2
0.164 kg/mol
= 213.6 m/s
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