JEE MAIN - Chemistry (2010)

1
One mole of a symmetrical alkene on ozonolysis gives two moles of an aldehyde having a molecular mass of 44 u. The alkene is
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(C)
2–butene
2
The correct order of increasing basicity of the given conjugate bases (R = CH₃) is
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(D)
$$RCO\overline O$$ < HC = $$\overline C$$ < $$\overline NH_2$$ < $$\overline R$$
3
Out of the following, the alkene that exhibits optical isomerism is
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(C)
3–methyl–1–pentene
4
Solubility product of silver bromide is 5.0 $$\times$$ 10^–13. The quantity of potassium bromide (molar mass taken as 120g of mol^–1) to be added to 1 litre of 0.05 M solution of silver nitrate to start the precipitation of AgBr is :
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(B)
1.2 $$\times$$ 10^–9 g
5
In aqueous solution the ionization constants for carbonic acid are
K₁ = 4.2 x 10^–7 and K₂ = 4.8 x 10^–11
Select the correct statement for a saturated 0.034 M solution of the carbonic acid.
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(C)
The concentration of H⁺ and $$HCO_3^−$$ are approximately equal.
6
At 25°C, the solubility product of Mg(OH)₂ is 1.0 $$\times$$ 10^–11. At which pH, will Mg²⁺ ions start precipitating in the form of Mg(OH)₂ from a solution of 0.001 M Mg²⁺ ions?
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(B)
10
7
Three reactions involving $$H_2PO_4^−$$ are given below :

(i) H₃PO₄ + H₂O $$\to$$ H₃O⁺ + $$H_2PO_4^−$$

(ii) $$H_2PO_4^−$$ + H₂O $$\to$$ $$HPO_4^{2−}$$ + H₃O⁺

(iii) $$H_2PO_4^−$$ + OH^- $$\to$$H₃PO₄ + O^2-

In which of the above does $$H_2PO_4^−$$ act as an acid?
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(A)
(ii) only
8
For a particular reversible reaction at temperature T, ∆H and ∆S were found to be both +ve. If T_e is the temperature at equilibrium, the reaction would be spontaneous when :
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(B)
T > T_e
9
The standard enthalpy of formation of NH₃ is –46.0 kJ mol^–1. If the enthalpy of formation of H₂ from its atoms is –436 kJ mol^–1 and that of N2 is –712 kJ mol^–1, the average bond enthalpy of N–H bond in NH₃ is :
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(B)
+352 kJ mol^–1
10
Biuret test is not given by
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(A)
carbohydrates
11
In the chemical reactions,

the compounds $$'A'$$ and $$'B'$$ respectively are
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(C)
benzene diazonium chloride and fluorobenzene
12
The main product of the following reaction is

$$\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,\,$$ $${C_6}{H_5}C{H_2}CH\left( {OH} \right)CH{\left( {C{H_3}} \right)_2}\buildrel {conc.{H_2}S{O_4}} \over \longrightarrow \,?$$
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(A)
13
Consider the following bromides :

The correct order of $${S_N}1$$ reactive is
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(A)
$$B > C > A$$
14
From amongst the following alcohols the one that would react fastest with conc. HCl and anhydrous ZnCl₂, is
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(B)
2–Methylpropan–2–ol
15
A solution containing 2.675g of CoCl₃. 6NH₃ (molar mass = 267.5 g mol^–1) is passed through a cation exchanger. The chloride ions obtained in solution were treated with excess of AgNO₃ to give 4.78 g of AgCl (molar mass = 143.5 g mol^–1). The formula of the complex is : (At. Mass of Ag = 108 u)
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(A)
[Co(NH₃)₆]Cl₃
16
Which one of the following has an optical isomer ?
(en = ethylenediamine)
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(B)
[Co (en)₃]³⁺
17
29.5 mg of an organic compound containing nitrogen was digested according to Kjeldahl’s method and the evolved ammonia was absorbed in 20 mL of 0.1 M HCl solution. The excess of the acid required 15 mL of 0.1 M NaOH solution for complete neutralization. The percentage of nitrogen in the compound is
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(C)
23.7
18
The time for half life period of a certain reaction A $$\to$$ products is 1 hour. When the initial concentration of the reactant ‘A’, is 2.0 mol L^–1, how much time does it take for its concentration to come from 0.50 to 0.25 mol L^–1 if it is a zero order reaction ?
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(C)
0.25 h
19
Consider the reaction :

Cl₂(aq) + H₂S(aq) → S(s) + 2H⁺ (aq) + 2Cl^– (aq)

The rate equation for this reaction is rate = k [Cl₂] [H₂S]

Which of these mechanisms is/are consistent with this rate equation?

(A) Cl₂ + H₂S $$\to$$ H⁺ + Cl^– + Cl⁺ + HS^– (slow)

Cl⁺ + HS^– $$\to$$ H⁺ + Cl^– + S (fast)

(B) H₂S $$ \Leftrightarrow $$ H⁺ + HS^– (fast equilibrium)

Cl₂ + HS^– $$\to$$ 2Cl^– + H⁺ + S (slow)
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(D)
A only
20
The Gibbs energy for the decomposition of Al₂O₃ at 500^oC is as follows :

$${2 \over 3}A{l_2}{O_3}$$ $$\to$$ $${4 \over 3}Al + {O_2}$$, $${\Delta _r}G$$ = + 966 kJ mol^–1

The potential difference needed for electrolytic reduction of Al₂O₃ at 500^oC is at least :
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(C)
2.5 V
21
The correct order of $$E_{{M^{2 + }}/M}^o$$ values with negative sign for the four successive elements Cr, Mn, Fe and Co is :
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(A)
Mn > Cr > Fe > Co
22
On mixing, heptane and octane form an ideal solution. At 373 K, the vapour pressures of the two liquid components (heptane and octane) are 105 kPa and 45 kPa respectively. Vapour pressure of the solution obtained by mixing 25.0g of heptane and 35 g of octane will be (molar mass of heptane = 100 g mol^–1 and of octane = 114 g mol^–1)
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(A)
72.0 kPa
23
If sodium sulphate is considered to be completely dissociated into cations and anions in aqueous solution, the change in freezing point of water (∆T_f), when 0.01 mol of sodium sulphate is dissolved in 1 kg of water, is (K_f = 1.86 K kg mol^–1)
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(B)
0.0558 K
24
The correct sequence which shows decreasing order of the ionic radii of the elements is
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(D)
O^2– > F^– > Na⁺ > Mg²⁺ > Al³⁺
25
Ionisation energy of He⁺ is 19.6 x 10^–18 J atom^–1. The energy of the first stationary state (n = 1) of Li²⁺ is
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(B)
-4.41 x 10^–17 J atom^–1
26
The energy required to break one mole of Cl–Cl bonds in Cl₂ is 242 kJ mol^–1. The longest wavelength of light capable of breaking a single Cl – Cl bond is
(c = 3 x 10⁸ ms^–1 and N_A = 6.02 x 10²³ mol^–1)
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(D)
494 nm