List of top Questions asked in CBSE CLASS XII

A doctor has diagnosed a fall in haemoglobin levels of an adolescent girl. Which nutritional deficiency disorder does it indicate? List any two other symptoms which may be seen in her in this disorder.
Why is the ability of oxygen greater than fluorine to stabilise higher oxidation states of transition metals?
How do you prepare potassium manganate from pyrolusite ore?
Out of KMnO$_4$ and K$_2$MnO$_4$, which one is paramagnetic and why?
Write the reaction of D-Glucose with the following:
(a) HCN (b) Br$_2$ water (c) (CH$_3$CO)$_2$O
Write two differences between DNA and RNA.
Why is molecularity applicable only for elementary reactions and order is applicable for elementary as well as complex reactions?
Why can azeotropic mixture not be separated by fractional distillation?
Assertion (A): First ionisation enthalpy of Cr is lower than that of Zn.
Reason (R): Zinc is a non-transition element.
With increase in atomic number, the melting point of transition metals :
Write the reaction involved in the following :
Clemmensen reduction
An organic compound (X) having molecular formula C$_5$H$_{10$O can show various properties depending on its structures. Draw each of the structures if it :
shows Cannizzaro reaction.
Answer the following question:
Name two elements of 3d series for which the third ionisation enthalpies are quite high.
Complete the following ionic equations :
5SO$_3^{2-}$ + 2MnO$_4^-$ + 6H$^+$ ⟶ ?
Account for the following :
(I) The E$^\circ_{Mn^{2+}/Mn}$ value for manganese is highly negative, whereas E$^\circ_{Mn^{3+}/Mn^{2+}}$ is highly positive.
Calculate the emf of the following cell at 25$^\circ$C :
Zn(s) $\mid$ Zn$^{2+}$ (0.1 M) $\parallel$ H$^+$ (0.01 M) $\mid$ H$_2$(g) (1 bar), Pt(s)
Given: E$^\circ_{Zn^{2+}/Zn}$ = –0.76 V, E$^\circ_{2H^+/H_2}$ = 0.00 V, log 10 = 1
How can you convert propanenitrile to 1-aminopropane?

Write structure of the products of the following reactions:

Vinyl group directly attached with carboxylic acid should decrease acidity due to resonance, but it increases acidity. Explain.
Give reasons for the following:HCHO is more reactive than CH$_3$CHO towards addition of HCN.
Give reasons for the following:
Benzoic acid does not undergo Friedel-Crafts reaction.
Peptide linkage and Glycosidic linkage
Essential amino acids and Non-essential amino acids
Write two differences between Amylose and Amylopectin components of starch.
What is meant by negative deviation from Raoult’s law? Give an example. What type of azeotrope is formed by negative deviation?