Silane, SiH 4 , is the silicon analogue of methane, CH4. It is prepared industrially according to the following equations: Si ( s ) + 3HC1 ( g ) → HSiCl 3 ( l ) + H 2 ( g ) 4HSiCl 3 ( l ) → SiH 4 ( g ) + 3SiCl 4 ( l ) a. If 156 mL HSiCl 3 (d = 1.34 g/mL) is isolated when 15.0 L HC1 at 10.0 atm and 35°C is used, what is the percent yield of HSiCl 3 ? b. When 156 mL HSiCl 3 is heated, what volume of SiH 4 at 10.0 atm and 35°C will be obtained if the percent yield of the reaction is 93.1%?

Interpretation: The percent yield of HSiCl3 in the given reaction has to be calculated.

Concept introduction:

• Balance equation of a reaction is written according to law of conservation of mass.

• Number of moles of a substance, According to ideal gas equation,

Number of moles   =     Pressure  × VolumeR  ×  Temperature 

• Equation for mass of a substance from its density and volume, 

  Mass   =   Density × Volume

• Percent yield of reaction is the ratio of mass of actual yield to the mass of theoretical yield.

• Mole ratios between the reactant and a product of a reaction are depends upon the coefficients of reactant and product in a balanced chemical equation.

• Mass of a substance produced from its number of moles is,

Number of moles  ×  Molecular mass in grams  =   produced mass

• Number of moles of a substance from its given mass is,

Number of moles   =   Given   massMolecular mass

• According to ideal gas equation for finding volume of a gas,

Volume   =   Number of moles  ×  R  ×  Temperature    pressure

To determine: the percent yield of HSiCl3 in the given reaction.

To find: the number of moles of HCl reacted in the given reaction.

The number of moles of HCl is 5.93 mol .

The volume of HCl in the given reaction is given as 15 L .

The pressure is given as 10 atm .

The temperature is given as 35oC = (35+273) K = 308 K .

The equation for finding number of moles of a substance, According to ideal gas equation,

Number of moles   =     Pressure  × VolumeR  ×  Temperature 

Therefore,

The number of moles of HCl is,

nHCl   =   15L × 10 atm0.08206 L atm/Kmol × 308 K   =   5.93 mol

Hence,

The number of moles of HCl is 5.93 mol .

To find: the number of moles HSiCl3 in the given reaction.

The number of moles of HSiCl3 in the given reaction is 1.976 mol .

The balanced chemical equation for the given reaction is,

Si +  3HCl  →   HSiCl3 +  H2

Here,

The mole ratio between HSiCl3 and HCl is 1: 3 .

The number of moles of HCl is 5.93 mol , and then the number of moles HSiCl3 is,

5.93 mol HCl ×  1 mol HSiCl33 mol HCl  =  1.976 mol HSiCl3

Therefore,

Theoretical calculated number of moles of HSiCl3 in the given reaction is 1

Interpretation: The volume of SiH4 obtained in the given reaction has to be calculated.

Concept introduction:

• Balance equation of a reaction is written according to law of conservation of mass.

• Number of moles of a substance, According to ideal gas equation,

Number of moles   =     Pressure  × VolumeR  ×  Temperature 

• Equation for mass of a substance from its density and volume, 

  Mass   =   Density × Volume

• Percent yield of reaction is the ratio of mass of actual yield to the mass of theoretical yield.

• Mole ratios between the reactant and a product of a reaction are depends upon the coefficients of reactant and product in a balanced chemical equation.

• Mass of a substance produced from its number of moles is,

Number of moles  ×  Molecular mass in grams  =   produced mass

• Number of moles of a substance from its given mass is,

Number of moles   =   Given   massMolecular mass

• According to ideal gas equation for finding volume of a gas,

Volume   =   Number of moles  ×  R  ×  Temperature    pressure

To determine: the percent yield of HSiCl3 and the volume of SiH4 obtained in the given reaction.