List of top Questions asked in COMEDK UGET- 2025

In the normal adjustment of an astronomical telescope, the objective and eyepiece are 36 cm apart. If the magnifying power of the telescope is 8, find the focal lengths of the objective and eyepiece.
The zener voltage in the circuit shown is \( V_Z = 20 \, V \). The load resistance \( R_L = 5k\Omega \) and the resistance \( R_S = 10k\Omega \). If the input voltage is \( V_S = 100 \, V \), then the current through the zener diode in milliampere is:

If the mass numbers of two nuclei are in the ratio \( 5 : 2 \) and their diameters are in ratio \( 2 : 6 \). Then their nuclear densities will be in the ratio
The unit of universal gravitational constant is :
Which of the following is correct in the case of the Bohr model of atoms?
A. Predicts continuous emission spectra for all atoms
B. Assumes that the angular momentum of electrons is quantised
C. Predicts same emission spectrum for singly ionised neon atom and hydrogen atom
D. Predicts same emission spectrum for singly ionised neon atom and singly ionised helium atom
The interference pattern is obtained with two coherent light sources of intensity ratio \( 9 : 1 \). The ratio of \( \frac{I_{MAX}+I_{MIN}}{I_{MAX}-I_{MIN}} \) is \( \frac{\alpha}{\beta} \). The values of \( \alpha \) and \( \beta \) are:
The correct order of spin-only magnetic moments among the following is: [Given: Atomic numbers: Mn = 25, Fe = 26, Co = 27]
When one mole of a hydrocarbon \( C_aH_b \) undergoes complete combustion, it requires 7.5 moles of \( O_2 \) and results in the production of 6 moles of \( CO_2 \). Calculate the values of \( a \) and \( b \).
Match the reactions in Column I with the correct products given in Column II.

Match the reaction in Column I with the major product formed given in Column II.

Two statements, one Assertion and the other Reason are given. Choose the correct option. Assertion: For strong electrolytes, the plot of Molar conductivity versus Concentration gives a straight line with slope equal to +A and intercept equal to \( \lambda_m \).
Reason: For strong electrolytes, \( \lambda_m \) increases slowly with dilution due to an increase in the distance between the ions and increase in ionic mobility.
The rate constant for a zero order reaction \( A \rightarrow B + C \) is \( 6.0 \times 10^{-3} \, \text{mol L}^{-1} \, \text{s}^{-1} \). What would be the time taken for the initial concentration of A to decrease from 0.2 M to 0.024 M?
Two statements, one Assertion and the other Reason are given. Choose the correct option.
Assertion: Heterocyclic compounds like Pyridine and Thiophene are non-aromatic compounds.
Reason: According to Hückel's rule for a given compound to exhibit aromaticity, the molecule must be planar, cyclic system having delocalized \( (4n + 2) \pi \) electrons.
For the reaction \( P + Q \rightleftharpoons R + S \), carried out at 298 K, the equilibrium constant was found to be 169 and the initial concentrations of all reactants and products was 1.0 M. What is the equilibrium concentration of the reactants?

The standard reduction potential at 25°C for \( MnO_4^- / H^+ \) is \( +1.49 \, \text{V} \).

The given standard reduction potentials are:

  • \( Co^{3+}/Co^{2+} = +1.81 \, \text{V} \)
  • \( Cr^{3+}/Cr = -0.74 \, \text{V} \)
  • \( Au^{3+}/Au = +1.50 \, \text{V} \)
  • \( Ag^+/Ag = +0.80 \, \text{V} \)

We need to identify which species cannot be oxidized by \( MnO_4^- / H^+ \).

Concept: A species will be oxidized by \( MnO_4^- \) only if its reduction potential is less than \( +1.49 \, \text{V} \).

Thus, species with higher reduction potential than \( MnO_4^- \) cannot be oxidized.

Comparing values:

  • \( Co^{3+}/Co^{2+} = +1.81 \, \text{V} \) → cannot be oxidized
  • \( Au^{3+}/Au = +1.50 \, \text{V} \) → cannot be oxidized

Final Answer: \( Co^{3+}/Co^{2+} \) and \( Au^{3+}/Au \)

Choose the incorrect statement from the following.
The best method for the separation of o-nitrophenol and p-nitrophenol from their mixture is:
Which one of the following molecules attains greater stability on formation of its diatomic monovalent anion?
For the reaction \( \text{A}_2 + \text{B}_2 \rightarrow 2 \text{AB} \), \( \Delta H_f = -400 \, \text{kJ/mol} \). The bond dissociation enthalpies of \( \text{A}_2 \), \( \text{B}_2 \), and \( \text{AB} \) are in the ratio 1 : 0.75 : 1. What is the bond dissociation enthalpy of \( \text{B}_2 \) in kJ/mol?
Identify the reagents to be used to complete the given reaction.

An organic compound "A" reacts with \( \text{Zn}/\text{Hg} / \text{Conc. HCl} \) to form p-Xylene. It reduces Tollen's reagent and on oxidation with \( \text{KMnO}_4 / H^+ \) it yields 1,4-benzenedicarboxylic acid. Identify compound A.
The first ionisation enthalpy of Al in kJmol\(^{-1}\) is:
[Given the first ionisation enthalpy of Na, Mg and Si in kJmol\(^{-1}\) are 497, 738, and 787 respectively]
What is the standard electrode potential at 298 K for the reaction:
\[ \text{Cu}^{2+} + \text{e}^- \rightarrow \text{Cu}^+ \] Given: \( E^0_{\text{Cu}^{+}/\text{Cu}} = 0.5 \, \text{V} \) and \( E^0_{\text{Cu}^{2+}/\text{Cu}} = 0.335 \, \text{V} \)
Choose the coordination compound which does not exhibit Optical activity.
A dilute solution of an ionic compound \( A_3B \) has an osmotic pressure which is 6 times that of 0.02 M \( \text{MgCl}_2 \). What is the molar concentration of \( A_3B \), assuming that it undergoes complete dissociation in water?