Classify each of the following solids as ionic,
Question: Classify each of the following solids as ionic, metallic, molecular, network (covalent) or amorphous. (i)Tetra phosphorus decoxide (P4O10)(vii)Graphite (ii)Ammonium phosphate (NH4)3PO4(viii)Brass (iii)SiC(ix)Rb (iv)I2(x)LiBr (v)P4(xi)Si Solution: Ionic(ii)Ammonium phosphate (NH4)3PO4,(x)LiBr Metallic(viii)Brass,(ix)Rb Molecular(i)Tetra phosphorus decoxide (P4O10),(iv)I2, (v) P4. Covalent (network)(iii)SiC,(vii)Graphite,(xi)Si Amorphous(vi)Plastic...
Read More →The length of a line segment joining A (2, −3) and B is 10 units.
Question: The length of a line segment joiningA(2, 3) andBis 10 units. If the abscissa ofBis 10 units, then its ordinates can be(a) 3 or 9(b) 3 or 9(c) 6 or 27(d) 6 or 27 Solution: It is given that distance between $\mathrm{P}(2,-3)$ and $\mathrm{Q}(10, y)$ is 10 . In general, the distance between $\mathrm{A}\left(x_{1}, y_{1}\right)$ and $\mathrm{B}\left(x_{2}, y_{2}\right)$ is given by, $\mathrm{AB}^{2}=\left(x_{2}-x_{1}\right)^{2}+\left(y_{2}-y_{1}\right)^{2}$ So, $10^{2}=(10-2)^{2}+(y+3)^{2}...
Read More →What makes a glass different from a solid such as quartz?
Question: What makes a glass different from a solid such as quartz? Under what conditions could quartz be converted into glass? Solution: The arrangement of the constituent particles makes glass different from quartz. In glass, the constituent particles have short range order, but in quartz, the constituent particles have both long range and short range orders. Quartz can be converted into glass by heating and then cooling it rapidly....
Read More →Define the term 'amorphous'.
Question: Define the term 'amorphous'. Give a few examples of amorphous solids. Solution: Amorphous solids are the solids whose constituent particles are of irregular shapes and have short range order. These solids are isotropic in nature and melt over a range of temperature. Therefore, amorphous solids are sometimes called pseudo solids or super cooled liquids. They do not have definite heat of fusion. When cut with a sharp-edged tool, they cut into two pieces with irregular surfaces. Examples ...
Read More →What type of substances would make better permanent magnets,
Question: What type of substances would make better permanent magnets, ferromagnetic or ferrimagnetic. Justify your answer. Solution: Ferromagnetic substances would make better permanent magnets. In solid state, the metal ions of ferromagnetic substances are grouped together into small regions. These regions are called domains and each domain acts as a tiny magnet. In an unmagnetised piece of a ferromagnetic substance, the domains are randomly oriented. As a result, the magnetic moments of the d...
Read More →ABCD is a rectangle formed by the points
Question: $A B C D$ is a rectangle formed by the points $A(-1,-1), B(-1,4), C(5,4)$ and $D(5,-1)$. If $P, Q, R$ and $S$ be the mid points of $A B, B C, C D$ and $D A$ respectively, show that $P Q R S$ is a rhombus. Solution: Here, the pointsP,Q,RandSare the mid points ofAB,BC,CDandDArespectively. Then Coordinates of $P=\left(\frac{-1-1}{2}, \frac{-1+4}{2}\right)=\left(-1, \frac{3}{2}\right)$ Coordinates of $Q=\left(\frac{-1+5}{2}, \frac{4+4}{2}\right)=(2,4)$ Coordinates of $R=\left(\frac{5+5}{2}...
Read More →The coordinates of the fourth vertex of the rectangle formed by
Question: The coordinates of the fourth vertex of the rectangle formed by the points (0, 0), (2, 0), (0, 3) are(a) (3, 0)(b) (0, 2)(c) (2, 3)(d) (3, 2) Solution: We have to find the co-ordinates of forth vertex of the rectangle ABCD. We the co-ordinates of the vertices as (0, 0); (2, 0); (0, 3) Rectangle has opposite pair of sides equal. When we plot the given co-ordinates of the vertices on a Cartesian plane, we observe that the length and width of the rectangle is 2 and 3 units respectively. S...
Read More →A group 14 element is to be converted into n-type semiconductor by doping it with a suitable impurity.
Question: A group 14 element is to be converted into n-type semiconductor by doping it with a suitable impurity. To which group should this impurity belong? Solution: Ann-type semiconductor conducts because of the presence of extra electrons. Therefore, a group 14 element can be converted ton-type semiconductor by doping it with a group 15 element....
Read More →Ionic solids, which have anionic vacancies due to metal excess defect,
Question: Ionic solids, which have anionic vacancies due to metal excess defect, develop colour. Explain with the help of a suitable example. Solution: The colour develops because of the presence of electrons in the anionic sites. These electrons absorb energy from the visible part of radiation and get excited. For example, when crystals of NaCl are heated in an atmosphere of sodium vapours, the sodium atoms get deposited on the surface of the crystal and the chloride ions from the crystal diffu...
Read More →A cord is wound round the circumference of wheel of radius r.
Question: A cord is wound round the circumference of wheel of radius $\mathbf{r}$. The axis of the wheel is horizontal and the moment of inertia about it is I. A weight $\mathrm{mg}$ is attached to the cord at the end. The weight falls from rest. After falling through a distance 'h', the square of angular velocity of wheel will be:$\frac{2 g h}{I+m r^{2}}$2gh$\frac{2 m g h}{I+2 m r^{2}}$$\frac{2 m g h}{I+m r^{2}}$Correct Option: , 4 Solution: using energy conservation between $\mathrm{A}$ and $\...
Read More →If (−2, 1) is the centroid of the triangle having its vertices at
Question: If (2, 1) is the centroid of the triangle having its vertices at (x, 0) (5, 2), (8,y), thenx,ysatisfy the relation(a) 3x+ 8y= 0(b) 3x 8y= 0(c) 8x+ 3y= 0(d) 8x= 3y Solution: We have to find the unknown co-ordinates. The co-ordinates of vertices are $\mathrm{A}(x, 0) ; \mathrm{B}(5,-2) ; \mathrm{C}(-8, y)$ The co-ordinate of the centroid is (2, 1) We know that the co-ordinates of the centroid of a triangle whose vertices are $\left(x_{1}, y_{1}\right),\left(x_{2}, y_{2}\right),\left(x_{3...
Read More →Explain how vacancies are introduced in an ionic solid
Question: Explain how vacancies are introduced in an ionic solid when a cation of higher valence is added as an impurity in it. Solution: When a cation of higher valence is added to an ionic solid as an impurity to it, the cation of higher valence replaces more than one cation of lower valence so as to keep the crystal electrically neutral. As a result, some sites become vacant. For example, when Sr2+is added to NaCl, each Sr2+ion replaces two Na+ions. However, one Sr2+ion occupies the site of o...
Read More →What type of stoichiometric defect is shown by:
Question: What type of stoichiometric defect is shown by: (i)ZnS (ii)AgBr Solution: (i)ZnS shows Frenkel defect. (ii)AgBr shows Frenkel defect as well as Schottky defect....
Read More →Find the ratio in which the point P( −1, y), lying on the line segment joining points A(−3, 10) and B(6, −8) divides it.
Question: Find the ratio in which the pointP( 1,y), lying on the line segment joining pointsA(3, 10) andB(6, 8) divides it. Also, find the value ofy. Also, find the value ofy. Solution: Letkbe the ratio in whichP( 1,y) divides the line segment joining the pointsA(3, 10) andB(6, 8). Then $(-1, y)=\left(\frac{k(6)-3}{k+1}, \frac{k(-8)+10}{k+1}\right)$ $\Rightarrow \frac{k(6)-3}{k+1}=-1$ and $y=\frac{k(-8)+10}{k+1}$ $\Rightarrow k=\frac{2}{7}$ Substituting $k=\frac{2}{7}$ in $y=\frac{k(-8)+10}{k+1}...
Read More →What type of defect can arise when a solid is heated?
Question: What type of defect can arise when a solid is heated? Which physical property is affected by it and in what way? Solution: When a solid is heated, vacancy defect can arise. A solid crystal is said to have vacancy defect when some of the lattice sites are vacant. Vacancy defect leads to a decrease in the density of the solid....
Read More →An element with molar mass
Question: An element with molar mass 2.7 10-2kg mol-1forms a cubic unit cell with edge length 405 pm. If its density is 2.7 103 kg m3, what is the nature of the cubic unit cell? Solution: It is given that density of the element,d= 2.7103kg m3 Molar mass, M = 2.7102kg mol1 Edge length,a= 405 pm = 4051012m = 4.051010m It is known that, Avogadros number, NA= 6.0221023 mol1 Applying the relation, $d=\frac{z, M}{a^{3} \cdot \mathrm{N}_{\mathrm{A}}}$ $z=\frac{d \cdot a^{3} \mathrm{~N}_{\mathrm{A}}}{M}...
Read More →If the centroid of the triangle formed by the points (3, −5), (−7, 4),
Question: If the centroid of the triangle formed by the points (3, 5), (7, 4), (10, k) is at the point (k1), thenk=(a) 3(b) 1(c) 2(d) 4 Solution: We have to find the unknown co-ordinates. The co-ordinates of vertices are $\mathrm{A}(3,-5) ; \mathrm{B}(-7,4) ; \mathrm{C}(10,-k)$ The co-ordinate of the centroid is $(k,-1)$ We know that the co-ordinates of the centroid of a triangle whose vertices are $\left(x_{1}, y_{1}\right),\left(x_{2}, y_{2}\right),\left(x_{3}, y_{3}\right)$ is- $\left(\frac{x...
Read More →Four identical solid spheres each of mass ' m ' and radius ' a '
Question: Four identical solid spheres each of mass ' $m$ ' and radius ' $a$ ' are placed with their centres on the four corners of a square of side ' $b$ '. The moment of inertia of the system about one side of square where the axis of rotation is parallel to the plane of the square is :$\frac{4}{5} m a^{2}$$\frac{8}{5} m a^{2}+m b^{2}$$\frac{4}{5} m a^{2}+2 m b^{2}$$\frac{8}{5} m a^{2}+2 m b^{2}$Correct Option: , 4 Solution: $I=\frac{2}{5} m a^{2}+\frac{2}{5} m a^{2}+\left[\frac{2}{5} m a^{2}+...
Read More →Four identical solid spheres each of mass ' m ' and radius ' a '
Question: Four identical solid spheres each of mass ' $m$ ' and radius ' $a$ ' are placed with their centres on the four corners of a square of side ' $b$ '. The moment of inertia of the system about one side of square where the axis of rotation is parallel to the plane of the square is :$\frac{4}{5} m a^{2}$$\frac{8}{5} m a^{2}+m b^{2}$$\frac{4}{5} m a^{2}+2 m b^{2}$$\frac{8}{5} m a^{2}+2 m b^{2}$Correct Option: , 4 Solution: $I=\frac{2}{5} m a^{2}+\frac{2}{5} m a^{2}+\left[\frac{2}{5} m a^{2}+...
Read More →Which of the following lattices has the highest packing efficiency
Question: Which of the following lattices has the highest packing efficiency (i) simple cubic (ii) body-centred cubic and (iii) hexagonal close-packed lattice? Solution: Hexagonal close-packed lattice has the highest packing efficiency of 74%. The packing efficiencies of simple cubic and body-centred cubic lattices are 52.4% and 68% respectively....
Read More →A compound is formed by two elements M and N.
Question: A compound is formed by two elements M and N. The element N formsccpand atoms of M occupy 1/3rdof tetrahedral voids. What is the formula of the compound? Solution: Theccplattice is formed by the atoms of the element N. Here, the number of tetrahedral voids generated is equal to twice the number of atoms of the element N. According to the question, the atoms of element $M$ occupy $\frac{1}{3}$ rd of the tetrahedral voids. Therefore, the number of atoms of $M$ is equal to $2 \times \frac...
Read More →The base BC of an equilateral triangle ABC lies on y-axis. The coordinates of point C are (0, −3).
Question: The baseBCof an equilateral triangleABClies ony-axis. The coordinates of pointCare (0, 3).The origin is the midpoint of the base. Find the coordinates of the pointsAandB. Also, findthe coordinates of another pointDsuch thatABCDis a rhombus. Solution: Let (0,y) be the coordinates ofB. Then $0=\frac{-3+y}{2} \Rightarrow y=3$ Thus, the coordinates ofBare (0, 3).Here,AB=BC=ACand by symmetry the coordinates ofAlies onx-axis.Let the coordinates ofAbe (x, 0). Then $A B=B C \Rightarrow A B^{2}...
Read More →The coordinates of a point on x-axis which lies on the perpendicular
Question: The coordinates of a point on x-axis which lies on the perpendicular bisector of the line segment joining the points (7, 6) and (3, 4) are(a) (0, 2)(b) (3, 0)(c) (0, 3)(d) (2, 0) Solution: TO FIND: The coordinates of a point onxaxis which lies on perpendicular bisector of line segment joining points (7, 6) and (3, 4). Let P(x,y) be any point on the perpendicular bisector of AB. Then, PA=PB $\sqrt{(x-7)^{2}+(y-6)^{2}}=\sqrt{(x-(-3))^{2}+(y-4)^{2}}$ $(x-7)^{2}+(y-6)^{2}=(x+3)^{2}+(y-4)^{...
Read More →A compound forms hexagonal close-packed structure.
Question: A compound formshexagonal close-packedstructure. What is the total number of voids in 0.5 mol of it? How many of these are tetrahedral voids? Solution: Number of close-packed particles = 0.56.0221023= 3.0111023 Therefore, number of octahedral voids = 3.0111023 And, number of tetrahedral voids = 23.0111023= 6.0221023 Therefore, total number of voids = 3.0111023+ 6.0221023= 9.0331023...
Read More →What is the two dimensional coordination
Question: What is the two dimensional coordination number of a molecule insquare closepacked layer? Solution: In square close-packed layer, a molecule is in contact with four of its neighbours. Therefore, the two-dimensional coordination number of a molecule in square close-packed layer is 4....
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