Question

Be sure to answer all parts. During World War II, a portable source of hydrogen gas was needed for weather balloons, and solid metal hydrides were the most convenient form. Many metal hydrides react with water to generate the metal hydroxide and hydrogen. Two candidates were lithium hydride and magnesium hydride. What volume of gas is formed from 1.10 lb of each hydride at 750, torr and 27°C? LH, from LiH L H, from MgH

Answer 1

Pressure =750 torr =0.986 atm

Temperature = 27 0C =300.15 K

R =0.082057 L atm /mol K

Mass of LiH= MgH2 =1.10 lb = 498.952 g

Moles = mass/ molar mass

Molar mass of LiH =7.95 g/mol

Moles(n) of LiH= 498.952 g /7.95 g/mol = 62.76 moles

Molar mass of MgH2 = 26.32 g/mol

Moles(n) of MgH2 =498.952 g / 26.32 g/mol =18.95 moles

The volume of LiH is calculated below:

PV = nRT

0.986 atm $\times$ V =62.76 moles $\times$ 0.0821 L atm /mol K $\times$ 300.15 K

V =1568.51 L

The volume of MgH2 is calculated below:

PV=nRT

0.986 atm $\times$ V = 18.95 moles $\times$ 0.0821 L atm /mol K $\times$ 300.15 K

V =473.60 L

Volume of LiH =1568.51 L

Volume of MgH2 = 473.60 L