JEE Questions

The disperse phase in colloidal iron (III) hydroxide and colloidal gold is positively and negatively charged, respectively. Which of the following statements is NOT correct?

1. Coagulation in both sols can be  brought about by electrophoresis.
2. Sodium sulphate solution causes coagulation in both sols.
3. Mixing of the sols has no effect.
4. Magnesium chloride solution coagulates, the gold sol more readily than the iron (III) hydroxide sol.

In conversion of limestone to lime,

CaCO3(s) → CaO(s) + CO2(g)

The values of ΔH° and ΔS° are +179.1 kJ/mol and 160.2 J/K respectively at 298 K and 1 bar. Assuming that ΔH° and ΔS° do not change with temperature, temperature above which conversion of limestone to lime will be spontaneous is

1. 1200 K
2. 1118 K
3. 1008 K
4. 845 K

Standard entropy of X2, Y2 and XY3 are 60, 40 and 50 J K–1 mol–1, respectively. For the reaction, 1/2 X2 + 3/2 Y2 → XY3, ΔH = –30 kJ, to be at equilibrium, the temperature will be

1. 500 K
2. 750 K
3. 1000 K
4. 1250 K

The heat required to raise the temperature of 1 mole substance by 1°C is called

1. Thermal capacity
2. Molar heat capacity
3. Specific heat
4. None of these

For a first order reaction, (A) → products, the concentration of A changes from 0.1 M to 0.025 M in 40 minutes. The rate of reaction when the concentration of A is 0.01 M is

1. 3.47 x 10-5 M/min
2. 1.73 x 10-4 M/min
3. 1.73 x 10-5 M/min
4. 3.47 x 10-4 M/min

For the non-stoichiometric reaction 2A + B → C + D, the following kinetic data were obtained in three separate experiments, all at 298 K.

The rate law for the formation of C is

1. dc/dt = k[A]2[B]
2. dc/dt = k[A]
3. dc/dt = k[A][B]
4. dc/dt = k[A][B]2

A reaction involving two different reactants can never be

1. unimolecular reaction
2. bimolecular reaction
3. second order reaction
4. first order reaction

The rate of a chemical reaction doubles for every 10ºC rise of temperature. If the temperature is raised by 50ºC, the rate of the reaction increases by about

1. 10 times
2. 24 times
3. 32 times
4. 64 times

The following mechanism has been proposed for the reaction of NO with Br2 to form NOBr.

NO(g) + Br2(g) ↔ NOBr2(g)

NOBr2(g) + NO(g) → 2NOBr(g)

If the second step is the rate determining step, the order of the reaction with respect to NO(g) is

1. 0
2. 1
3. 2
4. 3

The half­-life of a radioisotope is four hours. If the initial mass of the isotope was 200 g, the mass remaining after 24 hours undecayed is

1. 1.042 g
2. 2.084 g
3. 3.125 g
4. 4.167 g

A reaction was found to be second order with respect to the concentration of carbon monoxide. If the concentration of carbon monoxide is doubled, with everything else kept the same, the rate of reaction will be

1. remain unchanged
2. increased by a factor of 4
3. doubled
4. tripled

The half ­life of a radioactive isotope is three hours. If the initial mass of the isotope were 256 g, the mass of it remaining undecayed after 18 hours would be

1. 16.0 g
2. 12.0 g
3. 8.0 g
4. 4.0 g

Conductivity (unit Siemen’s S) is directly proportional to area of the vessel and the concentration of the solution in it and is inversely proportional to the length of the vessel then the unit of the constant of proportionality is

1. S2 m2 mol-2
2. S-2 m2 mol
3. S m mol-1
4. S m2 mol-1

In a hydrogen­-oxygen fuel cell, combustion of hydrogen occurs to

1. remove adsorbed oxygen from electrode surface
2. produce high purity water
3. generate heat
4. create potential difference between the two electrodes

Which of the following is a redox reaction?

1. NaCl + KNO3 → NaNO3 + KCl
2. Mg(OH)2 + 2NH4Cl → MgCl2 + 2NH4OH
3. CaC2O4 + 2HCl → CaCl2 + H2C2O4
4. 2Zn + 2AgCN → 2Ag + Zn(CN)2

Freezing point of an aqueous solution is (-0.186)°C. Elevation of boiling point of the same solution is Kb = 0.512 °C, Kf = 1.86 °C, find the increase in boiling point.

1. 0.186 °C
2. 0.092 °C
3. 0.0512 °C
4. 0.2372 °C

The solubility product of a salt having general formula MX2, in water is 4 × 10–12. The concentration of M2+ ions in the aqueous solution of the salt is

1. 1.6 × 10–4 M
2. 1.0 × 10–4 M
3. 2.0 × 10–6 M
4. 4.0 × 10–10 M

The correct relationship between free energy change in a reaction and the corresponding equilibrium constant Kc is

1. ΔG° = RT ln Kc
2. -ΔG = RT ln Kc
3. -ΔG = RT ln Kc
4. -ΔG° = RT ln Kc

Among the following acids which has the lowest pKa value?

1. HCOOH
2. CH3CH2COOH
3. (CH3)2CH–COOH
4. CH3COOH

Solubility product of silver bromide is 5.0x10-13. The quantity of potassium bromide (molar mass taken as 120 g mol–1) to be added to 1 litre of 0.05 M solution of silver nitrate to start the precipitation of AgBr is

1. 6.2 x 10-5 g
2. 5.0 x 10-8 g
3. 1.2 x 10-9 g
4. 1.2 x 10-10 g

A mixture of ethyl alcohol and propyl alcohol has a vapour pressure of 290 mm at 300 K. The vapour pressure of propyl alcohol is 200 nm. If the mole fraction of ethyl alcohol is 0.6, its vapour pressure (in mm) at the same temperature will be

1. 300
2. 350
3. 360
4. 700

If α is the degree of dissociation of Na2SO4, the vant Hoff’s factor (i) used for calculating the molecular mass is

1. 1 + 2α
2. 1 - α
3. 1 + α
4. 1 - 2α

Which one of the following aqueous solutions will exhibit highest boiling point?

1. 0.01 M KNO3
2. 0.015 M urea
3. 0.01 M Na2SO4
4. 0.015 M glucose

Equimolal solutions in the same solvent have

1. Same boiling and same freezing points.
2. Different boiling and different freezing points.
3. Same freezing point but different boiling point.
4. Same boiling point but different freezing point.

Two solutions of a substance (non electrolyte) are mixed in the following manner:

480 ml of 1.5 M first solution + 520 mL of 1.2 M second solution

What is the molarity of the final mixture?

1. 2.70 M
2. 1.50 M
3. 1.344 M
4. 1.20 M

Benzene and toluene form nearly ideal solutions. At 20°C, the vapour pressure of benzene is 75 torr and that of toluene is 22 torr. The partial vapour pressure of benzene at 20°C for a solution containing 78 g of benzene and 46 g of toluene in torr is

1. 25
2. 37.5
3. 50
4. 53.5

In a 0.2 molal aqueous solution of a weak acid HX, the degree of ionization is 0.3. Taking Kf for water as 1.85, the freezing point of the solution will be nearest to

1. – 0.480 °C
2. – 0.360 °C
3. – 0.260 °C
4. + 0.480 °C

How many unit cells are present in a cube-shaped ideal crystal of NaCl of mass 1.00 g? [Atomic masses: Na = 23, Cl = 35.5]

1. 2.57 × 1021
2. 1.28 × 1021
3. 1.71 × 1021
4. 5.14 × 1021

In a compound, atoms of element Y form ccp lattice and those of element X occupy 2/3rd of tetrahedral voids. The formula of the compound will be

1. X2Y
2. X3Y4
3. X4Y3
4. X2Y3

If Z is a compressibility factor, van der Waals equation at low pressure can be written as

1. Z = 1+Pb/RT
2. Z = 1-a/(VRT)
3. Z = 1+RT/Pb
4. Z = 1-Pb/RT

Equal masses of methane and oxygen are mixed in an empty container at 25°C. The fraction of the total pressure exerted by oxygen is

1. 1/2
2. 1/3
3. 2/3
4. (1/3) * (273/298)

Lithium forms body centred cubic structure. The length of the side of its unit cell is 351 pm. Atomic radius of the lithium will be

1. 75 pm
2. 152 pm
3. 240 pm
4. 300 pm

According to the kinetic theory of gases, in an ideal gas, between two successive collisions a gas molecule travels

1. in a straight line path
2. in a wavy path
3. in a circular path
4. with an accelerated velocity

In van der Waals equation of state of the gas law, the constant b is a measure of

1. volume occupied by the molecules
2. intermolecular attraction
3. intermolecular repulsions
4. intermolecular collisions per unit volume

The correct order of bond angles (smallest first) in H2S, NH3, BF3 and SiH4 is

1. H2S < NH3 < SiH4 < BF3
2. NH3 < H2S < SiH4 < BF3
3. H2S < SiH4 < NH3 < BF3
4. H2S < NH3 < BF3 < SiH4

The bond order in NO is 2.5 while that in NO+ is 3. Which of the following statements is true for these two species?

1. Bond length is unpredictable
2. Bond length in NO+ is equal to that in NO
3. Bond length in NO+ is greater than in NO
4. Bond length in NO is greater than in NO+

The molecule having smallest bond angle is

1. AsCl3
2. PCl3
3. SbCl3
4. NCl3

A square planar complex is formed by hybridisation of which atomic orbitals?

1. s, px, py, pz
2. s, px, py, pz, d
3. d, s, px, py
4. s, px, py, pz, d, d

In Bohr series of lines of hydrogen spectrum, the third line from the red end corresponds to which one of the following interorbit jumps of the electron for Bohr orbits in an atom of hydrogen?

1. 2 → 5
2. 4 → 1
3. 5 → 2
4. 3 → 2

Which of the following sets of quantum numbers is correct for an electron in 4f orbital?

1. n = 4, l = 4, m = –4, s =-1/2
2. n = 4, l = 3, m = +4, s =+1/2
3. n = 3, l = 2, m = –2, s =+1/2
4. n = 4, l = 3, m = +1, s =+1/2

Which of the following statements in relation to the hydrogen atom is correct?

1. 3s orbital is lower in energy than 3p orbital
2. 3s, 3p and 3d orbitals all have the same energy
3. 3s and 3p orbitals are of lower energy than 3d orbital
4. 3p orbital is lower in energy than 3d orbital

Consider the following nuclear reactions:

23892M → XYN + 242He  ;  XYN → ABL + 2β+

The number of neutrons in the element L is

1. 146
2. 144
3. 142
4. 140

How many moles of magnesium phosphate, Mg3(PO4)2 will contain 0.25 mole of oxygen atoms?

1. 2.5 x 10-2
2. 0.02
3. 1.25 x 10-2
4. 3.125 x 10-2

If we consider that 1/6, in place of 1/12, mass of carbon atom is taken to be the relative atomic mass unit, the mass of one mole of a substance will

1. decrease twice
2. remain unchanged
3. increase two fold
4. be a function of the molecular mass of the substance

With increase of temperature, which of these changes?

1. molality
2. molarity
3. mole fraction
4. weight fraction of solute

What volume of hydrogen gas, at 273 K and 1 atm. pressure will be consumed in obtaining 21.6 g of elemental boron (atomic mass = 10.8) from the reduction of boron trichloride by hydrogen?

1. 89.6 L
2. 67.2 L
3. 44.8 L
4. 22.4 L

Number of atoms in 558.5 gram Fe (atomic weight of Fe = 55.85 g mol–1) is

1. twice that in 60 g carbon
2. 558.5 × 6.023 × 1023
3. half that in 8 g He
4. 6.023 × 1022

In the reaction,

2Al (s) + 6HCl (aq) → 2Al3+ (aq) + 6Cl (aq) + 3H2 (g)

1. 6 L HCl (aq) is consumed for every 3 L H2(g) produced
2. 11.2 L H2(g) at STP is produced for every mole HCl (aq) consumed
3. 33.6 L H2(g) is produced regardless of temperature and pressure for every mole Al that reacts
4. 67.2 L H2(g) at STP is produced for every mole Al that reacts

The molecular formula of a commercial resin used for exchanging ions in water softening is C8H7SO3Na (Mol. Wt. 206). What would be the maximum uptake of Ca2+ ions by the resin when expressed in mole per gram resin?

1. 2/309
2. 1/103
3. 1/206
4. 1/412

If 0 ≤ x < 2π, then the number of real values of x, which satisfy the equation

cos x + cos 2x + cos 3x + cos 4x = 0 is

1. 3
2. 5
3. 7
4. 9