The Integrated Circuits in Your Cell Phone and Computer Are

question 121

Multiple Choice

The integrated circuits in your cell phone and computer are made from the semiconductor silicon. The silicon is obtained from a really inexpensive starting material, sand, which is primarily SiO₂. One step in the purification of silicon is to separate it from solid impurities by forming the gas silicon tetrachloride. Given the following reactions, what is the overall enthalpy change in converting 1.00 mol of silicon dioxide into pure silicon? $$\begin{array} { l c } { \text { Reaction } } & \boldsymbol { \Delta } \boldsymbol { H } ^ { \circ } ( \mathbf { k J } ) \\\left. \mathrm { SiO } _ { 2 } ( s ) + 2 \mathrm { C } ( s ) \rightarrow \mathrm { Si } \text { (impure } s \right) + 2 \mathrm { CO } ( g ) & + 690 \\\mathrm { Si } ( \mathrm { impure } ) + 2 \mathrm { Cl } _ { 2 } ( g ) \rightarrow \mathrm { SiCl } _ { 4 } ( g ) & - 657 \\\mathrm { SiCl } _ { 4 } ( g ) + 2 \mathrm { Mg } ( s ) \rightarrow 2 \mathrm { MgCl } _ { 2 } ( s ) + \mathrm { Si } ( s ) & - 625\end{array}$$

---

Definitions:

Social Citizenship

The rights and duties of citizens which pertain to their social welfare and participation in the social life of the community, beyond merely legal or civil aspects.

Social Movements

Social movements are organized collective efforts by groups of people to bring about or resist social, political, or economic changes within a society.

Increasingly Violent

Describes a situation or trend where the frequency or intensity of violence is growing over time.

Increasingly Local

A trend or movement towards prioritizing local community issues, culture, and economies, often as a response to globalisation.