Chemistry Syllabus (JEE Main)
Q. If the enthalpy of a system increases, what can be inferred about the system?
A.
It is losing heat
B.
It is gaining heat
C.
It is at equilibrium
D.
It is undergoing a phase change
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Solution
An increase in enthalpy indicates that the system is gaining heat.
Correct Answer: B — It is gaining heat
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Q. If the enthalpy of reaction is -100 kJ, what can be said about the reaction?
A.
It absorbs heat
B.
It releases heat
C.
It is at equilibrium
D.
It requires energy input
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Solution
A negative enthalpy change indicates that the reaction releases heat, making it exothermic.
Correct Answer: B — It releases heat
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Q. If the entropy of a system increases, what can be inferred about the spontaneity of the process?
A.
The process is non-spontaneous
B.
The process is spontaneous
C.
The process is at equilibrium
D.
None of the above
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Solution
An increase in entropy indicates that the process is spontaneous, as per the second law of thermodynamics.
Correct Answer: B — The process is spontaneous
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Q. If the entropy of a system increases, what is the effect on Gibbs Free Energy at constant temperature?
A.
ΔG increases
B.
ΔG decreases
C.
ΔG remains constant
D.
ΔG becomes zero
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Solution
If entropy increases, ΔG decreases, making the reaction more favorable.
Correct Answer: B — ΔG decreases
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Q. If the equation x^2 - 5x + k = 0 has equal roots, what is the value of k?
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Solution
For equal roots, the discriminant must be zero. Thus, (-5)^2 - 4*1*k = 0 => 25 - 4k = 0 => k = 25/4 = 6.25.
Correct Answer: A — 5
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Q. If the equilibrium constant Kc for a reaction is 10 at a certain temperature, what is the value of Kc for the reverse reaction?
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Solution
The equilibrium constant for the reverse reaction is the reciprocal of the forward reaction, so Kc' = 1/Kc = 0.1.
Correct Answer: A — 0.1
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Q. If the equilibrium constant Kc for a reaction is 10, what can be said about the position of equilibrium?
A.
Products are favored
B.
Reactants are favored
C.
Equilibrium is at the center
D.
No conclusion can be drawn
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Solution
A Kc value greater than 1 indicates that the products are favored at equilibrium.
Correct Answer: A — Products are favored
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Q. If the forward reaction is exothermic, what effect does increasing the temperature have on the equilibrium position?
A.
Shifts to the right
B.
Shifts to the left
C.
No effect
D.
Increases the rate of reaction
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Solution
According to Le Chatelier's principle, increasing the temperature of an exothermic reaction shifts the equilibrium position to the left, favoring the reactants.
Correct Answer: B — Shifts to the left
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Q. If the mole fraction of a solute in a solution is 0.2, what is the mole fraction of the solvent?
A.
0.8
B.
0.2
C.
0.5
D.
0.6
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Solution
Mole fraction of solvent = 1 - mole fraction of solute = 1 - 0.2 = 0.8.
Correct Answer: A — 0.8
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Q. If the mole fraction of a solvent in a solution is 0.75, what is the vapor pressure of the solvent if its pure vapor pressure is 100 mmHg?
A.
75 mmHg
B.
100 mmHg
C.
25 mmHg
D.
50 mmHg
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Solution
According to Raoult's Law, the vapor pressure of the solvent in the solution is 0.75 * 100 mmHg = 75 mmHg.
Correct Answer: A — 75 mmHg
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Q. If the mole fraction of solute in a solution is 0.2, what is the mole fraction of the solvent?
A.
0.8
B.
0.2
C.
0.5
D.
0.6
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Solution
The mole fraction of the solvent is 1 - X_solute = 1 - 0.2 = 0.8.
Correct Answer: A — 0.8
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Q. If the osmotic pressure of a solution is 3.0 atm at 25 °C, what is the molarity of the solution? (R = 0.0821 L atm/(K mol))
A.
0.12 M
B.
0.15 M
C.
0.18 M
D.
0.20 M
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Solution
Molarity = π / (RT) = 3.0 / (0.0821 * 298) = 0.12 M
Correct Answer: C — 0.18 M
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Q. If the osmotic pressure of a solution is 3.0 atm, what is the molarity of the solution? (R = 0.0821 L atm/(K mol), T = 298 K)
A.
0.12 M
B.
0.15 M
C.
0.10 M
D.
0.20 M
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Solution
Molarity = π / (RT) = 3.0 / (0.0821 * 298) = 0.12 M
Correct Answer: B — 0.15 M
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Q. If the principal quantum number n = 4 and the azimuthal quantum number l = 2, what is the maximum number of electrons in this subshell?
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Solution
The maximum number of electrons in a subshell is given by 2(2l + 1). For l = 2, it is 2(2*2 + 1) = 10.
Correct Answer: C — 14
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Q. If the principal quantum number n = 4, what are the possible values of l?
A.
0, 1, 2, 3
B.
1, 2, 3, 4
C.
0, 1, 2, 3, 4
D.
0, 1, 2
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Solution
For n=4, l can take values 0, 1, 2, or 3.
Correct Answer: A — 0, 1, 2, 3
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Q. If the principal quantum number n = 4, what are the possible values of the azimuthal quantum number l?
A.
0, 1, 2, 3
B.
1, 2, 3, 4
C.
0, 1, 2, 3, 4
D.
0, 1, 2
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Solution
For n=4, l can take values from 0 to n-1, which are 0, 1, 2, and 3.
Correct Answer: A — 0, 1, 2, 3
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Q. If the quadratic equation x^2 + kx + 9 = 0 has no real roots, what is the condition on k?
A.
k < 6
B.
k > 6
C.
k < 0
D.
k > 0
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Solution
The discriminant must be less than zero: k^2 - 4*1*9 < 0 => k^2 < 36 => |k| < 6.
Correct Answer: B — k > 6
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Q. If the rate of a reaction doubles when the temperature is increased by 10°C, what is the approximate activation energy (Ea) of the reaction?
A.
20 kJ/mol
B.
40 kJ/mol
C.
60 kJ/mol
D.
80 kJ/mol
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Solution
Using the Arrhenius equation, a rule of thumb states that for every 10°C increase in temperature, the rate doubles if Ea is around 40 kJ/mol.
Correct Answer: B — 40 kJ/mol
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Q. If the roots of the equation x^2 + 3x + k = 0 are real and distinct, what is the range of k?
A.
k < 9
B.
k > 9
C.
k < 0
D.
k > 0
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Solution
For real and distinct roots, the discriminant must be positive: 3^2 - 4*1*k > 0 => 9 - 4k > 0 => k < 9.
Correct Answer: A — k < 9
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Q. If the roots of the equation x^2 + 5x + k = 0 are -2 and -3, find k.
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Solution
Using Vieta's formulas, k = (-2)(-3) = 6.
Correct Answer: B — 6
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Q. If the roots of the equation x^2 - 6x + k = 0 are 2 and 4, find the value of k.
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Solution
Using Vieta's formulas, k = 2 * 4 = 8.
Correct Answer: B — 10
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Q. If the solubility product (Ksp) of AgCl is 1.77 x 10^-10, what is the molar solubility of AgCl?
A.
1.77 x 10^-5 M
B.
1.77 x 10^-10 M
C.
1.77 x 10^-7 M
D.
1.77 x 10^-3 M
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Solution
Ksp = [Ag+][Cl-] = s^2, thus s = sqrt(1.77 x 10^-10) = 1.77 x 10^-5 M.
Correct Answer: C — 1.77 x 10^-7 M
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Q. If the temperature of a gas is doubled at constant pressure, what happens to its volume?
A.
It halves
B.
It doubles
C.
It remains the same
D.
It quadruples
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Solution
According to Charles's Law, at constant pressure, the volume of a gas is directly proportional to its temperature.
Correct Answer: B — It doubles
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Q. If the temperature of a system is increased, what happens to its entropy?
A.
It decreases
B.
It remains constant
C.
It increases
D.
It becomes zero
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Solution
As the temperature of a system increases, the kinetic energy of the particles increases, leading to greater disorder and thus an increase in entropy.
Correct Answer: C — It increases
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Q. If the vapor pressure of a pure solvent is 80 mmHg and a non-volatile solute is added, resulting in a vapor pressure of 60 mmHg, what is the mole fraction of the solvent in the solution?
A.
0.75
B.
0.50
C.
0.25
D.
0.80
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Solution
Using Raoult's Law, P_solution = X_solvent * P_pure_solvent; 60 mmHg = X_solvent * 80 mmHg; X_solvent = 60/80 = 0.75.
Correct Answer: A — 0.75
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Q. If the vapor pressure of a solution is 80 mmHg and the vapor pressure of the pure solvent is 120 mmHg, what is the mole fraction of the solvent in the solution?
A.
0.67
B.
0.33
C.
0.50
D.
0.75
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Solution
Using Raoult's Law, P_solution = X_solvent * P_solvent^0; 80 = X_solvent * 120; X_solvent = 80/120 = 0.67.
Correct Answer: A — 0.67
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Q. If the vapor pressure of pure solvent A is 100 mmHg, and the mole fraction of A in the solution is 0.6, what is the vapor pressure of the solution according to Raoult's Law?
A.
60 mmHg
B.
100 mmHg
C.
40 mmHg
D.
80 mmHg
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Solution
Using Raoult's Law, P_solution = X_A * P_A^0 = 0.6 * 100 mmHg = 60 mmHg.
Correct Answer: A — 60 mmHg
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Q. If the vapor pressure of pure solvent A is 100 mmHg, what is the vapor pressure of a solution containing 0.5 mole fraction of A?
A.
50 mmHg
B.
100 mmHg
C.
75 mmHg
D.
25 mmHg
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Solution
According to Raoult's Law, the vapor pressure of the solution is 0.5 * 100 mmHg = 50 mmHg.
Correct Answer: A — 50 mmHg
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Q. If the vapor pressure of pure solvent is 120 mmHg, what will be the vapor pressure of a solution containing 0.2 moles of solute in 1 mole of solvent?
A.
100 mmHg
B.
110 mmHg
C.
120 mmHg
D.
80 mmHg
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Solution
Using Raoult's Law, the vapor pressure of the solution is P_solution = P_solvent * X_solvent = 120 * (1/(1+0.2)) = 120 * (1/1.2) = 100 mmHg.
Correct Answer: B — 110 mmHg
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Q. If x + 4 = 10, what is the value of x?
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Solution
Subtracting 4 from both sides gives x = 6.
Correct Answer: B — 6
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