Practice free NEET NEET multiple-choice questions online with instant answers and detailed explanations. No login required.
Total number of possible isomers (both structural as well as stereoisomers) of cyclic ethers of molecular formula $\text{C}_4\text{H}_8\text{O}$ is:
THF (1), 2-methyloxetane (2 enantiomers), 3-methyloxetane (1), 2-ethyloxirane (2), 2,2-dimethyloxirane (1), 2,3-dimethyloxirane (cis-meso 1 + trans pair 2 = 3): total $= 10$.
Identify the correct orders against the property mentioned: A. $\text{H}_2\text{O} > \text{NH}_3 > \text{CHCl}_3$ – dipole moment. B. $\text{XeF}_4 > \text{XeO}_3 > \text{XeF}_2$ – number of lone pairs on central atom. C. O–H > C–H > N–O – bond length. D. $\text{N}_2 > \text{O}_2 > \text{H}_2$ – bond enthalpy. Choose the correct answer:
A is correct (1.85 > 1.47 > 1.04 D). D is correct (N₂ 945 > O₂ 498 > H₂ 436 kJ/mol). B is wrong (lone pairs: XeF₂ 3 > XeF₄ 2 > XeO₃ 1). C is wrong (bond length N–O > C–H > O–H).
Higher yield of NO in $\text{N}_2\text{(g)} + \text{O}_2\text{(g)} \rightleftharpoons 2\text{NO(g)}$ can be obtained at [$\Delta H$ of the reaction $= +180.7\ \text{kJ mol}^{-1}$]: A. higher temperature, B. lower temperature, C. higher concentration of N₂, D. higher concentration of O₂. Choose the correct answer:
The reaction is endothermic, so higher temperature (A) favours the forward reaction. Increasing reactant concentrations N₂ (C) and O₂ (D) also shifts equilibrium toward NO. Lower temperature (B) does not.
If the rate constant of a reaction is $0.03\ \text{s}^{-1}$, how much time does it take for $7.2\ \text{mol L}^{-1}$ concentration of the reactant to get reduced to $0.9\ \text{mol L}^{-1}$? (Given: $\log 2 = 0.301$)
First order ($s^{-1}$): $t = \dfrac{1}{k}\ln\dfrac{C_0}{C} = \dfrac{1}{0.03}\ln 8 = \dfrac{2.303\times3\times0.301}{0.03} \approx 69.3$ s.
Which one of the following reactions does NOT belong to "Lassaigne's test"?
Lassaigne's test detects N, S and halogens by fusion with sodium. The reduction of CuO by carbon is a combustion-based carbon detection, not part of Lassaigne's test.
The complex II of mitochondrial electron transport chain is also known as:
Complex II of the ETC is succinate dehydrogenase (succinate–ubiquinone oxidoreductase), the only enzyme common to both the Krebs cycle and the ETC.
Which one of the following statements refers to Reductionist Biology?
Reductionist biology studies living organisms by analysing their physico-chemical (physical and chemical) components and processes.
Given below are two statements:
Statement I: In the RNA world, RNA is considered the first genetic material evolved to carry out essential life processes. RNA acts as a genetic material and also as a catalyst for some important biochemical reactions in living systems. Being reactive, RNA is unstable.
Statement II: DNA evolved from RNA and is a more stable genetic material. Its double helical strands being complementary, resist changes by evolving repairing mechanism.
In the light of the above statements, choose the most appropriate answer:
Both statements correctly describe the RNA-world hypothesis and the subsequent evolution of the more stable, self-repairing DNA.
Epiphytes that are growing on a mango branch is an example of which of the following?
An epiphyte benefits (support/space) while the mango tree is unaffected — this is commensalism (+/0).
Which one of the following is an example of ex-situ conservation?
Ex-situ conservation protects organisms outside their habitat — e.g. zoos and botanical gardens. The others are in-situ.
Ready to ace NEET?
Free access · No credit card required
Yes. You can attempt every NEET question on this page for free without logging in, and check the correct answer with a detailed explanation instantly.
No account is required to attempt questions and view answers. A free account adds bookmarks, personal notes, and progress tracking.
The bank mixes NEET previous year questions (PYQs) with practice questions, each tagged with its exam appearances where applicable.