An important global challenge is improving the sustainability of chemical synthesis by maximizing atom economy. Titanium metal can be manufactured by reducing titanium(IV) chloride using either sodium (the Hunter process) or magnesium (the Kroll process):
Hunter process:
TiCl4(g)+4Na(l)→Ti(s)+4NaCl(s) \text{TiCl}_4(\text{g}) + 4\text{Na}(\text{l}) \rightarrow \text{Ti}(\text{s}) + 4\text{NaCl}(\text{s}) TiCl4(g)+4Na(l)→Ti(s)+4NaCl(s)Kroll process:
TiCl4(g)+2Mg(l)→Ti(s)+2MgCl2(s) \text{TiCl}_4(\text{g}) + 2\text{Mg}(\text{l}) \rightarrow \text{Ti}(\text{s}) + 2\text{MgCl}_2(\text{s}) TiCl4(g)+2Mg(l)→Ti(s)+2MgCl2(s)Using the values Ar(Ti)=47.9A_r(\text{Ti}) = 47.9Ar(Ti)=47.9, Ar(Cl)=35.5A_r(\text{Cl}) = 35.5Ar(Cl)=35.5, Ar(Na)=23.0A_r(\text{Na}) = 23.0Ar(Na)=23.0, and Ar(Mg)=24.3A_r(\text{Mg}) = 24.3Ar(Mg)=24.3, what is the difference in percentage atom economy for the production of titanium between these two processes?
The Kroll process has an atom economy that is 3.1%3.1\%3.1% higher than that of the Hunter process.
The Hunter process has an atom economy that is 3.1%3.1\%3.1% higher than that of the Kroll process.
The Kroll process has an atom economy that is 4.7%4.7\%4.7% higher than that of the Hunter process.
The Hunter process has an atom economy that is 0.1%0.1\%0.1% higher than that of the Kroll process.
81 exam-style questions on OCR GCSE Chemistry Improving processes and products. Each one has a worked solution and a mark scheme showing where the marks go.