
Silicon used in computer chips must have an impurity level below 10−9 (that is, fewer than one impurity atom for every 109 Si atoms). Silicon is prepared by the reduction of quartz (SiO2) with coke (a form of carbon made by the destructive distillation of coal) at about 2000°C:
Next, solid silicon is separated from other solid impurities by treatment with hydrogen chloride at 350°C to form gaseous trichlorosilane (SiCl3H):
Finally, ultrapure Si can be obtained by reversing the above reaction at 1000°C:
(a) Trichlorosilane has a vapor pressure of 0.258 atm at −2°C. What is its normal boiling point? Is trichlorosilane’s boiling point consistent with the type of intermolecular forces that exist among its molecules? (The molar heat of vaporization of trichlorosilane is 28.8 kJ/mol.) (b) What types of crystals do Si and SiO2 form? (c) Silicon has a diamond crystal structure (see Figure 11.28). Each cubic unit cell (edge length a = 543 pm) contains eight Si atoms. If there are 1.0 × 1013 boron atoms per cubic centimeter in a sample of pure silicon, how many Si atoms are there for every B atom in the sample? Does this sample satisfy the 10−9 purity requirement for the electronic grade silicon?
Figure 11.28 (a) The structure of diamond. Each carbon is tetrahedrally bonded to four other carbon atoms. (b) The structure of graphite. The distance between successive layers is 335 pm.
(a)

Interpretation:
The normal boiling point of trichlorosilane and its adherence to its intermolecular forces have to be found out and discussed.
Concept Introduction:
Boiling point is the temperature at which the vapor pressure will be in equilibrium with the external pressure which is normally
Vapour pressure: It is the pressure developed on the vapor when it is in contact with its liquid form or solid form. So, it is also known as equilibrium vapor pressure which establishes equilibrium between its gaseous vapor state and liquid state or solid state.
The trends of boiling points are only due to the strength of the intermolecular forces that are acting between the molecules of the given compounds.
Intermolecular forces are the forces existing between molecules, atoms, ions or dipoles and hence binds all the molecules of a definite physical state such as solid, liquid or gas state.
Explanation of Solution
The normal boiling point of trichlorosilane can be calculated using the Clausisus-Clapeyron equation:
The Clausius-Clapeyron equation:
Given:
Converting kilojoules into joules:
Converting temperature from Celsius to kelvin:
Substituting all these values in the Clausius-Clapeyron equation:
Converting the normal boiling point temperature from Kelvin into Celsius:
Therefore, the normal boiling point of trichlorosilane is
Intermolecular forces existing in trichlorosilane
There are three highly electronegative halogen atoms such as chlorine atoms in the trichlorosilane which are attached to the least electronegative atoms such as silicon and hydrogen atoms. So there will be permanent dipole moment in the molecule, due to the distinguishable electronegativity in it. Hence, the interactions between such molecules will be dipole-dipole interactions, which are strong intermolecular forces. Therefore, the normal boiling point is expected to be in positive integer, since more energy is required to break the strong intermolecular forces. The calculated boiling point of trichlorosilane is
(b)

Interpretation: The type of crystal formed by
Concept Introduction:
The major types of crystals are listed here:
- 1. Ionic crystals.
- 2. Covalent crystals.
- 3. Molecular crystals.
- 4. Metallic crystals.
Ionic crystals: The crystals that are composed of charged species such as anions and cations.
Covalent crystals: In covalent crystals, all the atoms will be connected in a three-dimensional network by covalent bonds.
Molecular crystals: In molecular crystal, the molecules occupying the lattice points will have attractive forces between them such as van der waals forces or hydrogen bonding.
Metallic crystals: All the lattice points are occupied by the same type of metal.
Explanation of Solution
(c)

Interpretation: The purity requirement for the electronic grade silicon, has to be checked out when boron atom is added to
Concept Introduction:
Silicon is being used in various electronic devices today, due its special and important properties such as superconducting property and electrical properties. Silicon can be doped which is a modification in its electrical properties. Silicon used in computer chips must have an impurity level below
Explanation of Solution
Given:
The edge length of cubic unit cell in the diamond structure of silicon is given as
Converting edge length from picometers into centimeters:
Calculating the volume of per unit cell:
The relation between edge length and volume is
So, the volume of per unit cell is
Calculating the number of unit cells per cubic centimetre:
Therefore, in the volume of
Calculating the number of
It is given that there are 8
So,
Thus, there will be
Calculating the purity of
Given that
It is now known that per centimetre sample of pure silicon have
So, per centimetre sample of pure silicon have
This implies that there will be fewer than one impurity atom for every
Want to see more full solutions like this?
Chapter 11 Solutions
EBK CHEMISTRY
- Draw the titration curve of (i) weak acid vs. strong base; (ii) weak acid vs. weakbase; (iii) diprotic acid with strong base (iii) triprotic acid with strong base.arrow_forwardComplete the reaction in the drawing area below by adding the major products to the right-hand side. If there won't be any products, because nothing will happen under these reaction conditions, check the box under the drawing area instead. Note: if the products contain one or more pairs of enantiomers, don't worry about drawing each enantiomer with dash and wedge bonds. Just draw one molecule to represent each pair of enantiomers, using line bonds at the chiral center. More... No reaction. my ㄖˋ + 1. Na O Me Click and drag to start drawing a structure. 2. H +arrow_forwardPredict the intermediate 1 and final product 2 of this organic reaction: NaOMe H+ + 1 2 H H work up You can draw 1 and 2 in any arrangement you like. Note: if either 1 or 2 consists of a pair of enantiomers, just draw one structure using line bonds instead of 3D (dash and wedge) bonds at the chiral center. Click and drag to start drawing a structure. X $ dmarrow_forward
- Predict the major products of this organic reaction: 1. NaH (20°C) 2. CH3Br ? Some notes: • Draw only the major product, or products. You can draw them in any arrangement you like. • Be sure to use wedge and dash bonds where necessary, for example to distinguish between major products that are enantiomers. • If there are no products, just check the box under the drawing area. No reaction. Click and drag to start drawing a structure. G Crarrow_forwardPredict the major products of this organic reaction: 1. LDA (-78°C) ? 2. Br Some notes: • Draw only the major product, or products. You can draw them in any arrangement you like. . • Be sure to use wedge and dash bonds where necessary, for example to distinguish between major products that are enantiomers. • If there are no products, just check the box under the drawing area. No reaction. Click and drag to start drawing a structure. Xarrow_forwardPlease draw the structuresarrow_forward
- Draw the missing intermediates 1 and 2, plus the final product 3, of this synthesis: 0 1. Eto 1. Eto- 1 2 2. MeBr 2. EtBr H3O+ A 3 You can draw the three structures in any arrangement you like. Explanation Check Click and drag to start drawing a structure.arrow_forwardDraw the missing intermediate 1 and final product 2 of this synthesis: 1. MeO- H3O+ 1 2 2. PrBr Δ You can draw the two structures in any arrangement you like. Click and drag to start drawing a structure.arrow_forwardWhat is the differences between: Glyceride and phosphoglyceride Wax and Fat Soap and Fatty acid HDL and LDL cholesterol Phospho lipids and sphingosine What are the types of lipids? What are the main lipid components of membrane structures? How could lipids play important rules as signaling molecules and building units? The structure variety of lipids makes them to play significant rules in our body, conclude breifly on this statement.arrow_forward
- What is the differences between DNA and RNA for the following: - structure - function - type What is the meaning of: - replication - transcription - translation show the base pair connection(hydrogen bond) in DNA and RNAarrow_forwardWhat is the IP for a amino acid- give an example what are the types of amino acids What are the structures of proteins The N-Terminal analysis by the Edman method shows saralasin contains sarcosine at the N-terminus. Partial hydrolysis of saralasin with dilute hydrochloric acid yields the following fragments: Try-Val-His Sar-Arg-Val His-Pro-Ala Val- Tyr- Val Arg-Val-Tyr What is the structure of saralasin?arrow_forwardWhat is the IP for a amino acid- give an example what are the types of amino acids What are the structures of proteins The N-Terminal analysis by the Edman method shows saralasin contains sarcosine at the N-terminus. Partial hydrolysis of saralasin with dilute hydrochloric acid yields the following fragments: Try-Val-His Sar-Arg-Val His-Pro-Ala Val- Tyr- Val Arg-Val-Tyr What is the structure of saralasin?arrow_forward
- Chemistry: Principles and PracticeChemistryISBN:9780534420123Author:Daniel L. Reger, Scott R. Goode, David W. Ball, Edward MercerPublisher:Cengage LearningChemistry: An Atoms First ApproachChemistryISBN:9781305079243Author:Steven S. Zumdahl, Susan A. ZumdahlPublisher:Cengage LearningGeneral Chemistry - Standalone book (MindTap Cour...ChemistryISBN:9781305580343Author:Steven D. Gammon, Ebbing, Darrell Ebbing, Steven D., Darrell; Gammon, Darrell Ebbing; Steven D. Gammon, Darrell D.; Gammon, Ebbing; Steven D. Gammon; DarrellPublisher:Cengage Learning
- Chemistry by OpenStax (2015-05-04)ChemistryISBN:9781938168390Author:Klaus Theopold, Richard H Langley, Paul Flowers, William R. Robinson, Mark BlaserPublisher:OpenStaxChemistryChemistryISBN:9781305957404Author:Steven S. Zumdahl, Susan A. Zumdahl, Donald J. DeCostePublisher:Cengage Learning





