Sand is converted to pure silicon in a three step process. The third step is SiCl₄(g) + 2Mg(s) $\rightarrow$ 2MgCl₂(s) + Si(s) , $\Delta$ H = -625.6 kJ
What is the enthalpy change when 25.0 mol of silicon tetrachloride is converted to elemental silicon?

Question

Sand is converted to pure silicon in a three step process. The third step is SiCl₄(g) + 2Mg(s)

\rightarrow

2MgCl₂(s) + Si(s) ,

\Delta

H = -625.6 kJ
What is the enthalpy change when 25.0 mol of silicon tetrachloride is converted to elemental silicon?

Quizplus · Accepted Answer

Using stoichiometry and the given enthalpy change, we can calculate the enthalpy change for the conversion of 1 mol of SiCl4 to Si:
ΔH = (-625.6 kJ / 2 mol SiCl4) = -312.8 kJ/mol SiCl4
Multiplying this by the number of moles (25.0) gives:
ΔH = (-312.8 kJ/mol SiCl4) x (25.0 mol SiCl4) = -7,820 kJ
which is option B with the answer in scientific notation, so the answer is C.

Sand Is Converted to Pure Silicon in a Three Step →\rightarrow→

Sand Is Converted to Pure Silicon in a Three Step $\rightarrow$