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Chemistry
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Showing 1–25 of 28 questions
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The value of Planck's constant is $6.63\times10^{-34}$ Js. The speed of light is $3\times10^{17}$ nm $s^{-1}$. Which value is closest to the wavelength in nanometer of a quantum of light with frequency of $6\times10^{15}$ $s^{-1}$?$\lambda = \frac{c}{\nu} = \frac{3\times10^{17}\ nm\,s^{-1}}{6\times10^{15}\ s^{-1}} = 50$ nm
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Which of the following is electron-deficient?$(BH_3)_2$ is $B_2H_6$, which has 3-centre-2-electron (B–H–B) bridge bonds.
So it is electron deficient. -
Which of the following statements about the interstitial compounds is incorrect?Interstitial compounds have high melting points, are very hard, retain metallic conductivity and are chemically inert.
So the statement that they are chemically reactive is incorrect. -
Which one of the following molecules contains no $\pi$ bond?$H_2O$ has only two O–H $\sigma$ bonds. $NO_2$, $CO_2$ and $SO_2$ all contain double bonds, i.e. $\pi$ bonds.
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Nylon is an example of:Nylon has polyamide linkages. It is formed by condensation of amine and carboxylic acid groups.
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$XeF_2$ is isostructural with:$XeF_2$ is $sp^3d$ hybridised with three lone pairs and is linear.
$ICl_2^-$ also has $sp^3d$ hybridisation with three lone pairs on iodine and is linear, so the two are isostructural. -
The basic structural unit of silicates is:Silicates are salts of silicic acid, $H_4SiO_4$.
$Si(OH)_4 \xrightarrow{-4H^+} SiO_4^{4-}$ (silicate ion, tetrahedral) -
Which of the following structure is similar to graphite?Boron nitride (BN) has a layered structure of hexagonal rings like graphite, and is called inorganic graphite.
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The structure of isobutyl group in an organic compound is:$(CH_3)_3C-$ is tert-butyl; $(CH_3)_2CH-CH_2-$ is isobutyl; $CH_3-CH(-)-CH_2-CH_3$ is sec-butyl; $CH_3CH_2CH_2CH_2-$ is n-butyl.
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The number of carbon atoms per unit cell of diamond unit cell is:The diamond cubic unit cell has eight corner atoms, six face-centred atoms and four more atoms inside the cell.
Number of atoms $= 8\times\frac{1}{8} + 6\times\frac{1}{2} + 4 = 1 + 3 + 4 = 8$ -
What is the maximum number of electrons that can be associated with the following set of quantum numbers? n = 3, l = 1 and m = −1n = 3, l = 1 and m = −1 represent one 3p orbital, which can hold a maximum of 2 electrons.
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A reaction having equal energies of activation for forward and reverse reactions has:$\Delta H = (E_a)_f - (E_a)_b$
Given $(E_a)_f = (E_a)_b$, so $\Delta H = 0$ -
At $25^\circ C$ molar conductance of 0.1 molar aqueous solution of ammonium hydroxide is 9.54 $ohm^{-1}cm^2mol^{-1}$ and at infinite dilution its molar conductance is 238 $ohm^{-1}cm^2mol^{-1}$. The degree of ionisation of ammonium hydroxide at the same concentration and temperature is:$\%\alpha = \frac{\Lambda_m^c}{\Lambda_m^\infty}\times100 = \frac{9.54}{238}\times100 = 4.008\%$
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Antiseptics and disinfectants either kill or prevent growth of microorganisms. Identify which of the following statements is not true:Dilute solutions of boric acid and hydrogen peroxide are weak antiseptics, so calling them strong antiseptics is not true.
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Which of the following does not give oxygen on heating?$(NH_4)_2Cr_2O_7 \xrightarrow{\Delta} N_2 + Cr_2O_3 + 4H_2O$
It does not produce $O_2$. -
Dipole-induced dipole interactions are present in which of the following pairs:Dipole-induced dipole interaction occurs between a polar and a non-polar species.
HCl is polar ($\mu \ne 0$) and He is non-polar ($\mu = 0$). -
Roasting of sulphides gives the gas X as a by-product. This is a colourless gas with choking smell of burnt sulphur and causes great damage to respiratory organs as a result of acid rain. Its aqueous solution is acidic, acts as a reducing agent and its acid has never been isolated. The gas X is:Roasting of sulphide ores gives $SO_2$, a colourless gas with a choking smell that causes acid rain.
Its aqueous solution, sulphurous acid ($H_2SO_3$), is a reducing agent and has never been isolated. -
Nitrobenzene on reaction with conc. $HNO_3/H_2SO_4$ at 80–100$^\circ C$ forms which one of the following products?
The mixture of conc. $HNO_3$ and conc. $H_2SO_4$ gives $NO_2^+$, which acts as the electrophile.
In nitrobenzene the $-NO_2$ group is meta-directing, so $NO_2^+$ attacks the meta position, giving 1,3-dinitrobenzene. -
Which of the following is a polar molecule?An unsymmetrical distribution of the electron cloud makes a molecule polar.
$XeF_4$ (square planar), $BF_3$ (trigonal planar) and $SiF_4$ (tetrahedral) are symmetrical, $\mu = 0$.
$SF_4$ has a see-saw shape with one lone pair, so $\mu \ne 0$. -
A button cell used in watches functions as following: $Zn(s) + Ag_2O(s) + H_2O(l) \rightleftharpoons 2Ag(s) + Zn^{2+}(aq) + 2OH^-(aq)$. If half cell potentials are $Zn^{2+}(aq) + 2e^- \rightarrow Zn(s)$; $E^\circ = -0.76$ V and $Ag_2O(s) + H_2O(l) + 2e^- \rightarrow 2Ag(s) + 2OH^-(aq)$; $E^\circ = 0.34$ V, the cell potential will be:$E^\circ_{cell} = (E^\circ_{R.P.})_{cathode} - (E^\circ_{R.P.})_{anode}$
$E^\circ_{cell} = 0.34 - (-0.76) = 1.10$ V -
Which of these is least likely to act as a Lewis base?$BF_3$ has an incomplete octet on boron and accepts an electron pair, so it is a Lewis acid.
$PF_3$, CO and $F^-$ have lone pairs to donate. -
Which of the following compounds will not undergo Friedel-Crafts reaction easily:The Friedel-Crafts reaction fails when a strongly deactivating group is attached to the benzene ring.
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Which is the monomer of Neoprene in the following?$n\,CH_2=C(Cl)-CH=CH_2$ (chloroprene) $\xrightarrow{\text{polymerisation}} \left[-CH_2-C(Cl)=CH-CH_2-\right]_n$ (neoprene, artificial rubber)
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$6.02\times10^{20}$ molecules of urea are present in 100 mL of its solution. The concentration of solution is:Number of moles $= \frac{6.02\times10^{20}}{6.02\times10^{23}} = 10^{-3}$ mol
Molar concentration $= \frac{n\times1000}{V_{solution}(mL)} = \frac{10^{-3}\times1000}{100} = 0.01$ M -
Maximum deviation from ideal gas is expected from:$NH_3$ shows maximum deviation from ideal behaviour because of strong dipole-dipole attraction between its molecules.