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JEE Chemistry Solved Question Paper 2018

Multiple Choice Questions

An alkali is titrated against an acid with methyl orange as indicator, which of the following is a correct combination?

Base Acid End Point

Strong Strong Pink to colourless
Base Acid End Point

Weak Strong Colourless to pink
Base Acid End Point

Strong Strong Pinkish Red to Yellow
Base Acid End Point

Weak Strong Yellow to Pinkish Red

The predominant form of histamine present in human blood is (pKa, Histidine = 6.0)

Which of the following lines correctly show the temperature dependence of equilibrium constant K, for an exothermic reaction?

A and D
A and B
B and C
C and D

The combustion of benzene (l) gives CO₂(g) and H₂O(l). Given that heat of combustion of benzene at constant volume is –3263.9 kJ mol^–1 at 250C; the heat of combustion (in kJ mol^–1) of benzene at constant pressure will be (R = 8.314 JK^–1 mol^–1)

–3267.6
4152.6
–452.46
3260

5.
The ratio of mass percent of C and H of an organic compound (C_XH_YO_Z) is 6: 1. If one molecule of the above compound (C_XH_YO_Z) contains half as much oxygen as required to burn one molecule of compound C_XH_Y completely to CO₂ and H₂O. The empirical formula of compound C_XH_YO_Z is

C₂H₄O₃

C₃H₆O₃

C₂H₄O

C₃H₄O₂

C₂H₄O₃

The ratio of mass % of C and H in C_xH_yO_z is 6: 1.
Therefore,
The ratio of mole % of C and H in C_xH_yO_z will be 1: 2.
Therefore x : y = 1 : 2, which is possible in options 1, 2 and 3.
Now oxygen required to burn C_xH_y

$C_{x} H_{y} + (x + \frac{y}{4}) O_{2} \overset{}{\to} x C O_{2} + \frac{y}{2} H_{2} O$

Now z is half of the oxygen atoms required to burn C_xH_y

$∴ z = \frac{(2 x + \frac{y}{2})}{2} = (x + \frac{y}{4})$

Now putting values of x and y from the given options:
Option (1), x = 2, y = 4

$z = (2 + \frac{4}{4}) = 3 O p t i o n 2, x = 3, y = 6 z = (3 + \frac{6}{4}) = 4.5 T h e r e f o r e c o r r e n c t (C_{2} H_{4} O_{3})$

Which of the following are Lewis acids?

BCl₃ and AlCl₃
PH₃ and BCl₃
AlCl₃ and SiCl₄
PH₃ and SiCl₄

According to molecular orbital theory, which of the following will not be a viable molecule?

$H_{2}^{2 -}$
$H e_{2}^{2 +}$
$H e_{2}^{+}$
$H_{2}^{-}$

Which of the following compounds contain(s) no covalent bond(s)?
KCl, PH₃, O2, B₂H₆, H₂SO₄

KCl, B₂H₆
KCl, B₂H₆, PH₃
KCl, H₂SO₄
KCl

Total number of lone pair of electrons in I₃^-ion is

10.

Hydrogen peroxide oxidises $F e (C N)_{6}]^{4 -} t o [F e (C N)_{6}]^{3 -}$ in acidic medium but reduces $[F e (C N)_{6}]^{3 -} t o [F e (C N)_{6}]^{4 -}$ in alkaline medium. The other products formed are, respectively