Recent questions tagged difficult

An element having atomic mass 60 has face-centered cubic unit cells.The edge length of the unit cell is 400pm.Find the density of the element.

asked Aug 1, 2014 by sreemathi.v

1 answer

KCl crystallizes in the same type of lattice as does $NaCl$.Given that,$\large\frac{r_{Na^+}}{r_{Cl^-}}=$$0.5,\large\frac{r_{Na^+}}{r_{K^+}}=$$0.7$.Calculate the ratio of the side of the unit cell for KCl to that for NaCl and the ratio of density of NaCl to that for KCl.

asked Aug 1, 2014 by sreemathi.v

1 answer

Explain the following with suitable examples: 12-16 and 13-15 group compounds.

asked Jul 31, 2014 by sreemathi.v

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Explain the following with suitable examples: Ferrimagnetism

asked Jul 31, 2014 by sreemathi.v

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Aluminium crystallises in a cubic close-packed structure. Its metallic radius is 125 pm.How many unit cells are there in $1.00cm^3$ of aluminium?

asked Jul 31, 2014 by sreemathi.v

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Aluminium crystallises in a cubic close-packed structure. Its metallic radius is 125 pm.What is the length of the side of the unit cell?

asked Jul 30, 2014 by sreemathi.v

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

asked Jul 30, 2014 by sreemathi.v

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The activation energy for a certain reaction is 76.7 kJ mol$^{-1}$. How many times faster will the reaction occur at 50$^\circ$C compared to 0$^\circ$C?

asked Jul 25, 2014 by balaji.thirumalai

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If a temperature increase from 20$^\circ$C to 35$^\circ$C triples the rate constant for a reaction, what is the value of the activation barrier for the reaction?

asked Jul 25, 2014 by balaji.thirumalai

1 answer

The decomposition of $N_2O_5$ is given by the following equation: $2\; N_2O_5\; (g) \rightarrow 4 NO_2\;(g) + O_2\;(g)$ At an initial $[N_2O_5]_0 = 3.15\; M$, the initial rate of reaction is $5.45 \times 10^{-5} \;M/s$ and when $[N_2O_5]_0 = 0.78\; M$, the initial rate of reaction is $1.35 \times 10^{-5}\; M/s$. What is the rate constant of this reaction?

asked Jul 24, 2014 by balaji.thirumalai

1 answer

Given are the standard reduction potentials of a some species.The value of $E^{\large\circ}$ will be about

asked Jul 24, 2014 by sreemathi.v

1 answer

List these atoms in order of decreasing size: Br, Cl, Ge, K, S.

asked Jul 23, 2014 by balaji.thirumalai

1 answer

Arrange the following monatomic ions in order of increasing atomic radii: P$^{3–}$, Cr$^{6+}$, Ca$^{2+}$, Cl$^{-}$, Ti$^{4+}$.

asked Jul 23, 2014 by balaji.thirumalai

1 answer

An arch is in the form of a semi-ellipse. It is 8 m wide and 2 m high at the centre. Find the height of the arch at a point 1.5 m from one end.

asked Jul 23, 2014 by thanvigandhi_1

1 answer

The cable of a uniformly loaded suspension bridge hangs in the form of a parabola. The roadway which is horizontal and 100 m long is supported by vertical wires attached to the cable, the longest wire being 30 m and the shortest being 6 m. Find the length of a supporting wire attached to the roadway 18 m from the middle.

asked Jul 23, 2014 by thanvigandhi_1

1 answer

An arch is in the form of a parabola with its axis vertical. The arch is 10 m high and 5 m wide at the base. How wide is it 2 m from the vertex of the parabola?

asked Jul 23, 2014 by thanvigandhi_1

1 answer

The Henry's law constant for the solubility of $N_2$ gas in water is $1.0\times 10^5$ atm.The mole fraction of $N_2$ in air is 0.8.The amount of $N_2$ from air dissolved in 10mol of water at 298K and 5 atm pressure is

asked Jul 23, 2014 by sreemathi.v

1 answer

Twenty grams of hemoglobin in 1L solution at 300K is separated from pure water by a semipermeable.At equilibrium,the height of solution (density $1gcm^{-3}$) in a tube dipped in solution is found to be 83.1mm higher than in the tube dipped in water.If $g=10ms^{-2}$ ,the molar mass of hemoglobin is about

asked Jul 23, 2014 by sreemathi.v

1 answer

The standard reduction potentials of $Cu^{2+}|Cu$ and $Cu^{2+}|Cu^+$ are 0.337V and 0.153V, respectively.The standard electrode potential of $Cu^+|Cu$ half cell is

asked Jul 22, 2014 by sreemathi.v

1 answer

A solution containing one mole per litre each of $Cu(NO_3)_2,AgNO_3,Hg_2(NO_3)_2$ is being electrolysed by using inert electrodes.The values of standard potentials are $E^{\large\circ}_{Ag^+|Ag}=0.80V,E^{\large\circ}_{Hg_2^{2+}|Hg}=0.79V,E^{\large\circ}_{Cu^{2+}|Cu}=0.34V,E^{\large\circ}_{Mg^{2+}|Mg}=-2.3V$ with increasing voltage,the sequence of deposition of metals on the cathode will be

asked Jul 22, 2014 by sreemathi.v

1 answer

Adding powdered Pb and Fe to a solution containing 1.0M in each of $Pb^{2+}$ and $Fe^{2+}$ ions would result into the formation of

asked Jul 22, 2014 by sreemathi.v

1 answer

Find the equations of the hyperbola satisfying the given conditions : Foci $(0, \pm \sqrt{ 10} )$ , passing through $(2,3 )$

asked Jul 21, 2014 by thanvigandhi_1

1 answer

Consider the cell potentials $E^{\large\circ}_{Mg^{2+}|Mg}=-2.37V$ and $E^{\large\circ}_{Fe^{3+}|Fe}=-0.04V$.The best reducing agent would be

asked Jul 21, 2014 by sreemathi.v

1 answer

Which of the following facts is not true?

asked Jul 21, 2014 by sreemathi.v

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A sample of wustite $Fe_xO$ contains one Fe(III) for every three Fe(II).Calculate the value of $x$

asked Jul 16, 2014 by sreemathi.v

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LiI occurs as cubical-closest packing.If the edge length of a unit cell is 624 pm,determine the ionic radii of $Li^+$ and $I^-$ ions.

asked Jul 16, 2014 by sreemathi.v

1 answer

$KCl$ crystallizes in the same type of lattice as does $NaCl$.Givn that $\large\frac{r_{Na^+}}{r_{Cl^-}}$$=0.5$ and $\large\frac{r_{Na^+}}{r_{K^+}}$$=0.7$.Calculate the ratio of the side unit cell for $KCl$ to that for $NaCl$,and the ratio of density of $NaCl$ to that of $KCl$

asked Jul 16, 2014 by sreemathi.v

1 answer

Find out the ratio of the mole-fraction of the Frenkel’s defect in $NaCl$ crystal at $4000\;K$ temperature. The amount of energy needed to form Frenkel’s defects and Schottky defects are respectively $2\;eV$ and $4\;eV$.

asked Jul 15, 2014 by balaji.thirumalai

1 answer

A car travels east at a speed of $30m/s^{-1}$ . It turns left through an angle of $90^{\circ}$ and continues to travel with the same speed. What is the change in its velocity ?

asked Jul 15, 2014 by meena.p

1 answer

Selenium (Se) is a group VI element (i.e. two columns to the right of Silicon on the periodic table). An extrinsic semiconductor is produced by doping Silicon (Si) with 1020 Selenium atoms per m3. Assuming saturation, calculate the conductivity of the extrinsic semiconductor.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

Estimate the conductivity ($\sigma_i$) and resistivity ($\rho_i$) of silicon atoms and electron-hole pairs at room temperature of $300^{\circ}\;K$ if every 10-millionth silicon atom is replaced by an atom of Indium.

asked Jul 13, 2014 by balaji.thirumalai

1 answer

Evaluate the correct Boolean Expression for the given circuit?

asked Jul 13, 2014 by balaji.thirumalai

1 answer

Find the equation of the circle passing through $(0,0)$ and making intercepts a and b on the coordinate axes.

asked Jul 13, 2014 by thanvigandhi_1

1 answer

Find the value of $g$ (in $m\;s^{-2}$) up to approximate significant figures stating the uncertainty in the value of $g$, given the following information:

asked Jul 12, 2014 by balaji.thirumalai

1 answer

In the following experiment, find the value of the density in g cm$^{-3}$ up to the appropriate significant figures, stating the uncertainty in the value of the density.

asked Jul 12, 2014 by balaji.thirumalai

1 answer

The mean and standard deviation of a set of $n_1$ observations are $\bar{x_1}$ and $s_1$ respectively , while the mean and standard deviation of another set of $n_2$ observations are $x_2$ and $s_2$ respectively. Show that the standard deviation of the combined set of $(n_1+n_2)$ observations is given by $ S.D= \sqrt {\large\frac{n_1 (s_1)^2 +n_2 (s_2)^2}{n_1+n_2} +\frac{n_1n_2(\bar {x_1} -\bar {x_2} )^2}{(n_1+n_2)^2}}$

asked Jul 9, 2014 by meena.p

1 answer

Let $a,b,c,d,e$ be the observations with mean m and standard deviations $S$. The standard deviation of the observations $a+k,b+k,c+k,d+k,e+k$ is

asked Jul 8, 2014 by meena.p

1 answer

A sample space consists of a elementary outcomes $e_1,e_2........e_9$ whose probabilities are $P(e_1)=P(e_2)=0.08,P(e_3)=P(e_4)=P(e_5)=.1,P(e_6)=P(e_7)=.2,P(e_8)=p(e_9)=0.07$.Suppose $A=\{e_1,e_5,e_8\},B=\{e_2,e_5,e_8,e_9\}$.Using the addition law of probability ,calculate $P(A \cup B)$ .

asked Jul 8, 2014 by sreemathi.v

1 answer

A card is drawn from a deck of 52 cards.Find the probability of getting a king or a heart or a red card.

asked Jul 8, 2014 by sreemathi.v

1 answer

A bag contains 8 red and 5 white balls.Three balls are drawn at random.Find the probability that one ball is red and two balls are white

asked Jul 8, 2014 by sreemathi.v

1 answer

Mean and standard deviation of $100$ observation were found to be $40$ and $10$ respectively . If at the times of calculation two observations were wrongly takes as $30$ and $70$ in place of $3$ and $27$ respectively. Find the correct standard deviation.

asked Jul 7, 2014 by meena.p

1 answer

Four candidates A,B,C,D have applied for the assignment to coach a school cricket team.If A is twice as likely to be selected as B,and B and C are given about the same chance of being selected,while C is twice as likely to be selected as D,what are the probabilities that A will not be selected?

asked Jul 7, 2014 by sreemathi.v

1 answer

Four candidates A,B,C,D have applied for the assignment to coach a school cricket team.If A is twice as likely to be selected as B,and B and C are given about the same chance of being selected,while C is twice as likely to be selected as D,what are the probabilities that C will be selected?

asked Jul 7, 2014 by sreemathi.v

1 answer

Following are the marks obtained , out of 100 by two students Ravi and Hashina in 10 tests: Who is more intelligent and who is more consistent?

asked Jul 7, 2014 by meena.p

1 answer

In a large metropolitan area ,the probabilities are 0.87,0.36,0.30 that a family (randomly chosen for a sample survey) owns a colour television set,a black and white television set,or both kinds of sets.What is the probability that a family owns either anyone or both kinds of sets?

asked Jul 7, 2014 by sreemathi.v

1 answer

Determine mean and standard deviation of first n terms of an A.P whose first term is 'a' and common difference d.

asked Jul 7, 2014 by meena.p

1 answer

Six new employees,two of whom are married to each other,are to be assigned six desks that are lined up in a row.If the assignment of employees to desks is made randomly,what is the probability that the married couple will have non adjacent desks?

asked Jul 7, 2014 by sreemathi.v

1 answer

Choose the correct answer from the given four options. One vertex of the equilateral triangle with centroid at the origin and one side as x + y – 2 = 0 is \[\] [Hint: Let ABC be the equilateral triangle with vertex A (h, k) and let D ($ \alpha , \beta $ ) be the point on BC. Then $ \large\frac{2\alpha + h}{3}$$=0 = \large\frac{2\beta + k}{3}$. Also $ \alpha + \beta -2 = 0$ and $ \bigg( \large\frac{k-0}{h-0} \bigg) $$ \times (-1) =-1]$

asked Jul 6, 2014 by thanvigandhi_1

1 answer

Choose the correct answer from the given four options. The point (4, 1) undergoes the following two successive transformations : \[\] (i) Reflection about the line $y=x$ \[\] (ii) Translation through a distance 2 units along the positive x-axis \[\] Then the final coordinates of the point are

asked Jul 6, 2014 by thanvigandhi_1

1 answer

Find the mean and variance of the frequency distribution given below:

asked Jul 4, 2014 by meena.p

1 answer

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