Chemistry Syllabus (JEE Main)
Q. In a reaction at equilibrium, if the concentration of a reactant is decreased, what will happen?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Increase the rate of reaction
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Solution
According to Le Chatelier's principle, decreasing the concentration of a reactant will shift the equilibrium to the left to produce more reactants.
Correct Answer: B — Shift to the left
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Q. In a reaction at equilibrium, if the concentration of products increases, what will happen to the equilibrium position?
A.
Shift to the left
B.
Shift to the right
C.
No change
D.
Depends on temperature
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Solution
According to Le Chatelier's principle, if the concentration of products increases, the equilibrium will shift to the left.
Correct Answer: A — Shift to the left
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Q. In a reaction at equilibrium, if the concentration of products is decreased, what will happen?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Depends on the temperature
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Solution
Decreasing the concentration of products will shift the equilibrium to the right to produce more products, according to Le Chatelier's principle.
Correct Answer: A — Shift to the right
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Q. In a reaction at equilibrium, if the concentration of reactants is increased, what will happen to the equilibrium?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Equilibrium constant increases
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Solution
According to Le Chatelier's principle, increasing the concentration of reactants will shift the equilibrium to the right to form more products.
Correct Answer: A — Shift to the right
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Q. In a reaction at equilibrium, if the concentration of reactants is increased, what will happen to the equilibrium position?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Depends on the reaction
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Solution
According to Le Chatelier's principle, increasing the concentration of reactants will shift the equilibrium position to the right to produce more products.
Correct Answer: A — Shift to the right
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Q. In a reaction at equilibrium, if the temperature is decreased, what will happen to the equilibrium position if the reaction is exothermic?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Depends on the concentration
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Solution
For an exothermic reaction, decreasing the temperature shifts the equilibrium to the right, favoring the formation of products.
Correct Answer: A — Shift to the right
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Q. In a reaction at equilibrium, if the temperature is increased and the reaction is exothermic, what will happen to the equilibrium position?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Equilibrium constant increases
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Solution
For an exothermic reaction, increasing the temperature shifts the equilibrium position to the left, favoring the reactants.
Correct Answer: B — Shift to the left
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Q. In a reaction at equilibrium, if the temperature is increased, what will happen to the equilibrium constant Kc for an endothermic reaction?
A.
Increase
B.
Decrease
C.
No change
D.
Depends on concentration
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Solution
For an endothermic reaction, increasing temperature shifts the equilibrium to the right, increasing Kc.
Correct Answer: A — Increase
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Q. In a reaction mechanism, the slowest step is known as the:
A.
Rate-determining step
B.
Intermediate step
C.
Fast step
D.
Catalytic step
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Solution
The slowest step in a reaction mechanism is called the rate-determining step, as it controls the overall reaction rate.
Correct Answer: A — Rate-determining step
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Q. In a reaction mechanism, the slowest step is known as what?
A.
Rate-determining step
B.
Intermediate step
C.
Fast step
D.
Catalytic step
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Solution
The slowest step in a reaction mechanism is known as the rate-determining step.
Correct Answer: A — Rate-determining step
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Q. In a reaction where 2 moles of hydrogen react with 1 mole of oxygen, how many moles of water are produced?
A.
1 mole
B.
2 moles
C.
3 moles
D.
4 moles
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Solution
According to the balanced equation 2H2 + O2 → 2H2O, 2 moles of H2 produce 2 moles of H2O.
Correct Answer: B — 2 moles
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Q. In a reaction where ΔH is positive and ΔS is negative, what is the sign of ΔG at high temperatures?
A.
Positive
B.
Negative
C.
Zero
D.
Cannot be determined
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Solution
At high temperatures, ΔG will be positive because the positive ΔH and negative ΔS will dominate the equation ΔG = ΔH - TΔS.
Correct Answer: A — Positive
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Q. In a reaction, 3 moles of A react with 2 moles of B to produce 4 moles of C. What is the mole ratio of A to C?
A.
3:4
B.
2:3
C.
4:3
D.
1:1
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Solution
The mole ratio of A to C is 3:4 based on the coefficients in the balanced equation.
Correct Answer: A — 3:4
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Q. In a reaction, if the enthalpy change (ΔH) is -100 kJ and the entropy change (ΔS) is 200 J/K, what is the Gibbs free energy change (ΔG) at 298 K?
A.
-100 kJ
B.
-50 kJ
C.
0 kJ
D.
50 kJ
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Solution
ΔG = ΔH - TΔS = -100 kJ - (298 K * 0.2 kJ/K) = -100 kJ - 59.6 kJ = -159.6 kJ.
Correct Answer: A — -100 kJ
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Q. In a reaction, if the rate constant doubles when the temperature increases by 10°C, what is the activation energy (Ea) approximately?
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, Ea can be estimated to be around 40 kJ/mol.
Correct Answer: B — 40 kJ/mol
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Q. In a redox reaction, which species is reduced?
A.
Oxidizing agent
B.
Reducing agent
C.
Product
D.
Reactant
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Solution
The oxidizing agent is the species that gains electrons and is reduced.
Correct Answer: A — Oxidizing agent
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Q. In a reversible process, the change in entropy of the universe is:
A.
Positive
B.
Negative
C.
Zero
D.
Undefined
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Solution
In a reversible process, the change in entropy of the universe is zero, as the system and surroundings are in equilibrium.
Correct Answer: C — Zero
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Q. In a reversible process, the change in Gibbs free energy (ΔG) is:
A.
Always positive
B.
Always negative
C.
Zero at equilibrium
D.
None of the above
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Solution
In a reversible process, the change in Gibbs free energy (ΔG) is zero at equilibrium.
Correct Answer: C — Zero at equilibrium
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Q. In a reversible process, the change in Gibbs free energy is equal to:
A.
Zero
B.
Enthalpy
C.
Entropy
D.
Temperature
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Solution
In a reversible process at equilibrium, the change in Gibbs free energy is zero.
Correct Answer: A — Zero
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Q. In a solution of 1 mol of solute in 9 mol of solvent, what is the mole fraction of the solute?
A.
0.1
B.
0.2
C.
0.5
D.
0.9
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Solution
Mole fraction of solute = moles of solute / (moles of solute + moles of solvent) = 1 / (1 + 9) = 0.1.
Correct Answer: A — 0.1
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Q. In a solution of 1 mole of solute B in 3 moles of solvent A, what is the mole fraction of solvent A?
A.
0.25
B.
0.75
C.
0.33
D.
0.67
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Solution
Mole fraction of A = moles of A / (moles of A + moles of B) = 3 / (3 + 1) = 0.75.
Correct Answer: B — 0.75
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Q. In a solution of a non-volatile solute, how does the addition of solute affect the boiling point of the solvent?
A.
It decreases the boiling point
B.
It has no effect on the boiling point
C.
It increases the boiling point
D.
It depends on the nature of the solute
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Solution
The addition of a non-volatile solute raises the boiling point of the solvent, a phenomenon known as boiling point elevation.
Correct Answer: C — It increases the boiling point
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Q. In a solution of a non-volatile solute, how does the vapor pressure compare to that of the pure solvent?
A.
Higher than the pure solvent
B.
Lower than the pure solvent
C.
Equal to the pure solvent
D.
Depends on the temperature
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Solution
The presence of a non-volatile solute lowers the vapor pressure of the solvent compared to that of the pure solvent.
Correct Answer: B — Lower than the pure solvent
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Q. In a solution of two volatile components A and B, if the mole fraction of A is 0.6, what is the vapor pressure of the solution if the vapor pressure of pure A is 100 mmHg and that of pure B is 50 mmHg?
A.
80 mmHg
B.
90 mmHg
C.
70 mmHg
D.
60 mmHg
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Solution
Using Raoult's Law, the vapor pressure of the solution is P_total = (0.6 * 100) + (0.4 * 50) = 60 + 20 = 80 mmHg.
Correct Answer: B — 90 mmHg
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Q. In a solution of volatile components A and B, if the vapor pressure of A is 80 mmHg and that of B is 20 mmHg, what is the total vapor pressure?
A.
100 mmHg
B.
80 mmHg
C.
60 mmHg
D.
20 mmHg
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Solution
The total vapor pressure of a solution is the sum of the partial vapor pressures of its components: 80 mmHg + 20 mmHg = 100 mmHg.
Correct Answer: A — 100 mmHg
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Q. In a spontaneous process, the change in Gibbs free energy (ΔG) is:
A.
Positive
B.
Negative
C.
Zero
D.
Undefined
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Solution
For a spontaneous process, the change in Gibbs free energy (ΔG) is negative.
Correct Answer: B — Negative
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Q. In a static equilibrium problem, if the sum of clockwise moments equals the sum of counterclockwise moments, what can be concluded?
A.
The object is in equilibrium
B.
The object is accelerating
C.
The object is in motion
D.
The object is unstable
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Solution
If the sum of clockwise moments equals the sum of counterclockwise moments, the object is in equilibrium.
Correct Answer: A — The object is in equilibrium
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Q. In a system at equilibrium, if the concentration of reactants is increased, what will happen to the equilibrium position?
A.
Shift to the right
B.
Shift to the left
C.
No change
D.
Depends on temperature
Show solution
Solution
According to Le Chatelier's principle, increasing the concentration of reactants will shift the equilibrium position to the right to favor the formation of products.
Correct Answer: A — Shift to the right
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Q. In a system of two blocks connected by a spring, if the spring is compressed, what is the condition for equilibrium?
A.
Net force acting on the system is zero
B.
Net momentum of the system is constant
C.
Kinetic energy is maximized
D.
Potential energy is minimized
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Solution
For equilibrium, the net force acting on the system must be zero.
Correct Answer: A — Net force acting on the system is zero
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Q. In a system where two forces act at an angle of 90 degrees, how do you find the resultant force?
A.
By adding the forces algebraically
B.
Using the Pythagorean theorem
C.
By taking the average of the two forces
D.
By subtracting the smaller force from the larger force
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Solution
The resultant force can be found using the Pythagorean theorem since the forces are perpendicular.
Correct Answer: B — Using the Pythagorean theorem
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