Recent questions tagged ch-1

Earth receives enormous amount of energy from sunlight. The problem of shortage of power can be solved if we could convert solar energy into electricity. A device which generates electrical power from sunlight is called solar cell or photovoltaic cell. Solar cells are made up of silicon doped with arsenic and silicon doped with boron. Answer the following questions: (i) When silicon is doped with arsenic, what type of semiconductor is obtained? Explain. (ii) What type of semiconductor is obtained by doping silicon with boron? (iii) Give any two applications (other than solar cells) of semiconductors.

asked Nov 28, 2016 by meena.p

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Evaluate :$\sec^2 (\tan^{-1}(2)) + cosec^2(\cot^{-1}(3))$

asked Nov 23, 2016 by priyanka.c

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Analysis shows that nickel oxide has the formula $Ni0_{98}O_{1.00}$. What fractions of nickel exist as $Ni^{2+}$ and $Ni_{3+}$ ions?

asked Nov 23, 2016 by meena.p

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Give reason (a) window glass of old building look milky. (b) window glass of old building is thick at bottom (c) $Cacl_2$ will introduced schotlky defect if added to $Agcl$ crystal

asked Nov 23, 2016 by meena.p

1 answer

$18\;g$ of glucose , $C_6H_{12}$ is dissolved in $1\;kg$ of water in a sauce pan. At what temperature will water boil at $1.013$ bar ? $K_b$ for water is $0.52\;k\;kg\;mol^{-1}$

asked Nov 21, 2016 by meena.p

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How is ferromagnetism different from paramagnetism

asked Nov 21, 2016 by meena.p

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Why does the electrical conductivity of semiconductor increase in temperature ?

asked Nov 21, 2016 by meena.p

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Gold (atomic mass $=197\;v$ atomic radius $=0.144\;nm$) crystallizers in a face centered unit cell . Determined the density of gold $[N_A=6.022 \times 10^{23}mol^{-1}]$

asked Nov 14, 2016 by meena.p

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Why is an increase in temperature observed on mixing chloroform with acetone ?

asked Nov 9, 2016 by meena.p

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Ionic solid conduct in the molten state but not in the solid state . Explain

asked Nov 9, 2016 by meena.p

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Copper crystallizer into an fcc lattice with edge length $3.61 \times 10^{-8}\;cm$ Show that the calculated density is in agreement with its measured value of $8.92 \;g\;cm^{-3}$

asked Nov 4, 2016 by meena.p

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Define the following terms in relation to crystalline solids . (i) Unit cell (ii) Coordination number . Give one example in each case

asked Nov 2, 2016 by meena.p

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If the radius of the octahedral void is r and the radius of the atoms in the close packing is R, derive relationship between r and R.

asked Oct 26, 2016 by meena.p

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What type of defect can arises when a solid is heated ? Which physical properly is affected by it and in what way ?

asked Oct 26, 2016 by meena.p

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Aluminium crystallizes in a cubic - packed structure . Radius of the atom in the metal is $125\;pm$ (i) What is the length of the side of the unit cell ? (ii) How many unit cells are there in $1\;cm^3$ of aluminium ?

asked Oct 25, 2016 by meena.p

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A compound is formed by two elements, M and N . The element N forms CCP and atoms of M occupy $\large\frac{1}{3}$ rd of tetrahedral voids . What is the formula of the compound?

asked Oct 21, 2016 by meena.p

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Sodium crystallizes in a bcc unit cell , calculate the appropriate number of unit cell in $9.2\;g$ of sodium (Atomic mass of Na=23 u)

asked Oct 19, 2016 by meena.p

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(a) Calculate the charge in coulombs required for oxidation for 2 moles of water to oxygen. [Given $IF= 96,500\;c\;mol^{-1}$] (b) Zinc / Silver oxide cell is used is hearing aids and electric watches . The following reaction occur. $Zn(S) \to Z_n^{2+} (aq)+2e^{-} E^0_{Zn^{2+}/Zn}=-0.76\;V \\ Ag_20+H_2O+2e^{-} \to 2Ag +2 OH - E^0_{Ag^{+}/Ag}=0.344\;V$ Calculate (i) Standard potential of the cell (ii) Standard Gibbs energy .

asked Oct 19, 2016 by meena.p

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In $Nacl$ crystal each b$cl^{-}$ ion is surrounded by

asked Sep 9, 2015 by meena.p

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In an antiflorite structure , cations occupy

asked Sep 9, 2015 by meena.p

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Total volume of atoms present in face - centered cubic unit cell of metal is (r is atomic radius)

asked Sep 9, 2015 by meena.p

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In a face-centered cubic lattice , a unit cell is shared equally by how many units cells?

asked Sep 9, 2015 by meena.p

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The appearance of colour in solid alkali metal halides is generally due to

asked Sep 9, 2015 by meena.p

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The fraction of total volume occupied by the atoms present in a simple cube is

asked Sep 9, 2015 by meena.p

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The crystal with metal deficiency defect is

asked Sep 8, 2015 by meena.p

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The coordination number of $Al$ in the crystalline state of $Alcl_3$ is

asked Sep 8, 2015 by meena.p

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Number of unit cells in $4\;g$ of $\times $ (atomic mass =40) Which crystallize in bcc pattern is $(N_A= Avogadro \; number)$

asked Sep 8, 2015 by meena.p

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The white $z_no$ turns yellow on heating because of

asked Sep 8, 2015 by meena.p

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The radius ratio in $CsCl$ is $0.93$. The expected lattice structure is

asked Sep 8, 2015 by meena.p

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The number of tetrahedral voids in the unit cell of a face centred cubic lattice of similar atoms is

asked Sep 8, 2015 by meena.p

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The number of hexagonal faces that are present in truncated octahedron is

asked Sep 8, 2015 by meena.p

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The conic radii of $Rb^+$ and $ I^-$ are $1.46\;A^{\circ}$ and $2.16\;A^{\circ}$ respectively . The most probable type of structure exhibited by it is

asked Sep 8, 2015 by meena.p

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The efficiency of packing is $68 \%$ in

asked Sep 8, 2015 by meena.p

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The ability of a given substance to assume two or more crystalline structure is called

asked Sep 8, 2015 by meena.p

2 answers

Which one of the following is a covalent crystal ?

asked Sep 8, 2015 by meena.p

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Which of the following statements about amorphous solids is incorrect?

asked Sep 8, 2015 by meena.p

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Density of a crystal remains unchanged as a result of

asked Sep 8, 2015 by meena.p

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To get n-type doped semiconductor , the impurity to be added to silicon should have the following numbers of valence electrons ?

asked Sep 8, 2015 by meena.p

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Relationship between atomic radius(r) and the edge length of a body centred cubic unit cell is

asked Sep 8, 2015 by meena.p

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In $Nacl$ crystal each $cl^{-}$ ion is surrounded by

asked Sep 8, 2015 by meena.p

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In an antifluorite structure , cations occupy

asked Sep 8, 2015 by meena.p

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In a face centred cubic (fcc) arrangement, the number of atoms per unit cell is

asked Sep 8, 2015 by meena.p

2 answers

If the distance between $Na^{+}$ and $cl^{-}$ions in sodium chloride crystal is $xpm$, the length of the edge of the unit cell is

asked Sep 8, 2015 by meena.p

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A p- type materialy is electrically

asked Sep 8, 2015 by meena.p

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A metallic crystal having bcc type staking pattern , what percentage of volume of this lattice is empty .

asked Sep 8, 2015 by meena.p

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A compound formed by element A and B crystallizes in the cubic. Structure where A atoms are at the coiners of the cube and B atoms are at face centers. The formula of the compound is

asked Sep 8, 2015 by meena.p

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In which of the following crystal alternate tetrahedral voids are occupied ?

asked Sep 8, 2015 by meena.p

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An conic compound is expected to have tetrahedral structure if $\large\frac{r^+}{r^-}$ lies in the range of

asked Sep 8, 2015 by meena.p

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A compound contains two types of atoms X and Y. It crystallizes in a cubic lattice with atoms X at the coiner of the unit cell and atoms Y at the body center. The simplest possible formula of this compound is

asked Sep 8, 2015 by meena.p

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Percentage of free space in cubic close packed structure and in body centered packed structure are respectively

asked Sep 8, 2015 by meena.p

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