Chemistry (School & UG)

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Q. A chemical reaction releases 250 J of heat. If the reaction occurs at constant pressure, what is the change in enthalpy?
  • A. -250 J
  • B. 250 J
  • C. 0 J
  • D. 500 J
Q. A process absorbs 300 J of heat and does 100 J of work. What is the change in internal energy (ΔU)?
  • A. 200 J
  • B. 300 J
  • C. 400 J
  • D. 100 J
Q. A reaction has an enthalpy change of 200 kJ for the formation of 1 mole of product. What is the enthalpy change for the formation of 0.5 moles of product?
  • A. 100 kJ
  • B. 200 kJ
  • C. 50 kJ
  • D. 400 kJ
Q. According to Graham's Law, how does the rate of effusion of a gas relate to its molar mass?
  • A. Inversely proportional
  • B. Directly proportional
  • C. Equal
  • D. Unrelated
Q. According to Graham's Law, the rate of effusion of a gas is inversely proportional to what?
  • A. Its molar mass
  • B. Its temperature
  • C. Its pressure
  • D. Its volume
Q. According to the Kinetic Molecular Theory, which of the following is NOT a postulate?
  • A. Gas particles are in constant random motion.
  • B. Gas particles occupy a definite volume.
  • C. Collisions between gas particles are elastic.
  • D. The average kinetic energy is proportional to temperature.
Q. According to Werner's theory, what is the coordination number of a complex with six ligands?
  • A. 2
  • B. 4
  • C. 6
  • D. 8
Q. According to Werner's theory, what type of isomerism is primarily observed in coordination compounds?
  • A. Geometric isomerism
  • B. Optical isomerism
  • C. Structural isomerism
  • D. All of the above
Q. At constant temperature, what happens to the pressure of a gas if its volume is halved?
  • A. Pressure doubles
  • B. Pressure halves
  • C. Pressure remains the same
  • D. Pressure quadruples
Q. At constant temperature, what happens to the pressure of a gas if its volume is doubled?
  • A. Pressure doubles
  • B. Pressure halves
  • C. Pressure remains the same
  • D. Pressure quadruples
Q. At what temperature does the Kelvin scale start?
  • A. 0°C
  • B. 100°C
  • C. 273.15°C
  • D. 0 K
Q. At which conditions do real gases behave most like ideal gases?
  • A. High pressure and low temperature
  • B. Low pressure and high temperature
  • C. High pressure and high temperature
  • D. Low pressure and low temperature
Q. Calculate the change in enthalpy (ΔH) when 2 moles of a substance absorb 500 J of heat at constant pressure.
  • A. 250 J/mol
  • B. 500 J/mol
  • C. 1000 J/mol
  • D. 125 J/mol
Q. Calculate the dipole moment of a molecule with a charge of 1.6 x 10^-19 C and a bond length of 1.5 Å.
  • A. 2.4 x 10^-29 C·m
  • B. 2.4 x 10^-28 C·m
  • C. 2.4 x 10^-30 C·m
  • D. 2.4 x 10^-31 C·m
Q. Calculate the dipole moment of HCl given that the bond length is 1.27 Å and the charge separation is 0.33 e.
  • A. 1.1 D
  • B. 0.4 D
  • C. 0.8 D
  • D. 0.2 D
Q. Calculate the enthalpy change (ΔH) for the reaction: 2NO(g) + O2(g) → 2NO2(g) given the following bond enthalpies: N≡N = 941 kJ/mol, O=O = 498 kJ/mol, N=O = 201 kJ/mol.
  • A. -180 kJ
  • B. -200 kJ
  • C. -220 kJ
  • D. -240 kJ
Q. Calculate the formal charge on a nitrogen atom in NH3.
  • A. 0
  • B. +1
  • C. -1
  • D. +2
Q. Calculate the formal charge on the nitrogen atom in NO3-.
  • A. 0
  • B. -1
  • C. +1
  • D. +2
Q. Calculate the Gibbs free energy change (ΔG) for a cell with E° = 0.75 V and n = 2 moles of electrons transferred.
  • A. -150 kJ
  • B. -75 kJ
  • C. 75 kJ
  • D. 150 kJ
Q. Calculate the ionization energy of hydrogen in eV if the energy level is -13.6 eV.
  • A. 13.6 eV
  • B. 1.24 eV
  • C. 3.4 eV
  • D. 0.85 eV
Q. Calculate the ionization energy of hydrogen in eV if the energy of the electron in the ground state is -13.6 eV.
  • A. 13.6 eV
  • B. 1.24 eV
  • C. 3.4 eV
  • D. 27.2 eV
Q. Calculate the molar mass of water (H2O).
  • A. 16 g/mol
  • B. 18 g/mol
  • C. 20 g/mol
  • D. 22 g/mol
Q. Determine the bond angle in a tetrahedral molecule like CH4.
  • A. 90°
  • B. 109.5°
  • C. 120°
  • D. 180°
Q. For a first-order reaction, if the half-life is 10 minutes, what is the rate constant?
  • A. 0.0693 min^-1
  • B. 0.1 min^-1
  • C. 0.693 min^-1
  • D. 0.5 min^-1
Q. For a first-order reaction, if the half-life is 10 minutes, what will be the half-life if the concentration is doubled?
  • A. 10 minutes
  • B. 20 minutes
  • C. 5 minutes
  • D. It cannot be determined
Q. For a molecule with a bond length of 1.2 Å and a bond order of 2, what is the bond energy in kJ/mol?
  • A. 500
  • B. 600
  • C. 700
  • D. 800
Q. For a reaction A → B, if the rate constant k is 0.1 s^-1, what is the time required for the concentration of A to decrease to 25% of its initial value?
  • A. 10 seconds
  • B. 20 seconds
  • C. 30 seconds
  • D. 40 seconds
Q. For a reaction at equilibrium, if the concentration of products is increased, what will happen to the position of equilibrium according to Le Chatelier's principle?
  • A. Shift to the right
  • B. Shift to the left
  • C. No change
  • D. Depends on temperature
Q. For a reaction at equilibrium, if the temperature is increased and ΔH is positive, what will happen to the position of equilibrium?
  • A. Shift to the right
  • B. Shift to the left
  • C. No change
  • D. Depends on concentration
Q. For a reaction at equilibrium, what happens if the concentration of a reactant is increased?
  • A. The equilibrium shifts to the right
  • B. The equilibrium shifts to the left
  • C. The equilibrium remains unchanged
  • D. The reaction stops
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