List of top Chemistry Questions

An alkyne \(X\) \((C_4H_6)\) does not form sodium alkynide. Reaction of \(X\) with HBr gave \(Y\). Another reaction of \(X\) with \(Na/\text{liq. }NH_3\) gave \(Z\). Identify \(Y\) and \(Z\).

A compound is formed by \(A\) (cations), \(B\) (cations) and \(O\) (anions). Atoms of \(O\) form a ccp lattice. Atoms of \(A\) occupy \(50\%\) of octahedral voids and atoms of \(B\) occupy \(25\%\) of tetrahedral voids. What is the molecular formula of the compound?

Identify the correct statements from the following I) \[ \text{Conjugate base of nitrous acid is } NO_2^{-} \] II) \[ \text{The concentration of } OH^{-} \text{ ions in } 0.1\,M \text{ aqueous pyridine solution is } \sqrt{2}\times10^{-5}\,M \] \[ (K_b \text{ of pyridine }=2\times10^{-9}) \] III) The acid strength of aqueous hydrogen halides follows \[ HF \gt HCl \gt HBr \gt HI \]

At \(450\,K\), for the reaction \[ 2SO_2(g)+O_2(g)\rightleftharpoons 2SO_3(g), \] the value of \[ K_p=2.0\times10^{10}. \] What is the value of \(K_c\) for the decomposition of sulphur trioxide at the same temperature? \[ R=0.083\ \text{L bar mol}^{-1}\text{K}^{-1} \]

At \(298\,K\), for the reaction \[ N_2(g)+3H_2(g)\rightleftharpoons 2NH_3(g) \] \[ \Delta H=-92.4\ \text{kJ} \] and \[ \log K_c=5.75. \] What is the entropy change \((\Delta S)\) (in J K\(^{-1}\)) for this reaction at the same temperature? \[ (R=8.3\ \text{J K}^{-1}\text{mol}^{-1}) \]

Observe the following unbalanced reactions \[ KO_2 \xrightarrow{\;HOH\;} X + Y\uparrow + KOH \] \[ KMnO_4 \xrightarrow[\text{basic medium}]{\;X\;} Y + Z + KOH + H_2O \] Y and Z are respectively

Identify the sets in which both the metals react with water? \[ \text{I.}\quad Be,\ Mg \] \[ \text{II.}\quad Li,\ Mg \] \[ \text{III.}\quad Na,\ K \] \[ \text{IV.}\quad K,\ Ca \]

The reaction between \(X\) and \(Y\) produces a solid substance and a mixture of two gases, one of which is a colourless toxic gas. \(X\) and \(Y\) respectively are

Which of the following sets contain isostructural molecules? I. \[ H_2O,\ OF_2,\ SCl_2 \] II. \[ CO_2,\ BeCl_2,\ HgCl_2 \] III. \[ SiCl_4,\ SF_4,\ XeF_4 \]

Formal charge on sulphur atom in the following three Lewis structures I, II and III respectively is \[ \text{I.}\quad \ddot{S}=C=\ddot{N} \] \[ \text{II.}\quad :S-C\equiv N: \] \[ \text{III.}\quad :S\equiv C-N: \]

At \(27^\circ C\), a real gas of molar mass \[ 44\ \text{g mol}^{-1} \] occupies a volume of \[ 0.4\ \text{L} \] at a pressure of \[ 40\ \text{atm}. \] If the compressibility factor is \[ Z=0.65, \] what is its weight (in g)? \[ (R=0.082\ \text{L-atm K}^{-1}\text{mol}^{-1}) \]

At \(298\,K\), the value of \((\Delta H-\Delta U)\) for the combustion of 1 mole of \[ C_4H_{10}(g) \] is \(x\) kJ and for the combustion of 1 mole of glucose, the value of \[ (\Delta H-\Delta U) \] is \(y\) kJ. The value of \((x-y)\) (in kJ) is \[ (R=8.3\ \text{J K}^{-1}\text{mol}^{-1}) \]

Which of the following statements are correct? I. In the third period, two elements have higher ionization enthalpy than the element immediately following them in the same period. II. Electronegativity of carbon is higher than that of phosphorus. III. An element \(X\) belongs to group 14 and period 3. The number of electrons present in it is \(14\).

\(x\) mL of \(0.05\,M\) \(KMnO_4\) solution is required to oxidise completely \(1.52\) g of \(FeSO_4\) in acidic medium. The value of \(x\) is \[ (\text{Atomic weights: } Fe=56,\ S=32,\ O=16) \]

The number of radial nodes possible for \(3p\)-orbital is \(x\) and the number of angular nodes possible for \(4d\)-orbital is \(y\). What is \(x:y\)?

Threshold frequencies of the metals \(A\) and \(B\) are respectively \[ 4\times10^{14}\ \text{Hz} \] and \[ 6\times10^{14}\ \text{Hz}. \] If both are irradiated with light of frequency \[ 10^{15}\ \text{Hz}, \] what is the ratio of the kinetic energies of electrons emitted from \(A\) and \(B\)?

Why is o-nitrophenol more acidic than o-methoxyphenol?

What happens when acidic solution of potassium permanganate is allowed to stand for sometime ? Give the equation involved. What is this type of reaction called ?

By usual analysis, 1.00 g of compound (X) gave 1.79 g of magnesium pyrophosphate. The percentage of phosphorus in compound (X) is : _________ (nearest integer)
(Given, molar mass in g mol\(^{-1}\) ; O = 16, Mg = 24, P = 31)}

Which gas is evolved when zinc reacts with dilute hydrochloric acid?

A molecule \( (X) \) with the following structure under mild acidic conditions is hydrolyzed to produce \( (Y) \) and \( (Z) \). Identify the correct statements about \( (Y) \) and \( (Z) \).}

For the following reaction choose the incorrect expression of rate of reaction. \[ 5\text{ Br}^{-}(aq.) + \text{BrO}_{3}^{-}(aq.) + 6\text{ H}^{+}(aq.) \rightarrow 3\text{ Br}_{2}(aq.) + 3\text{ H}_{2}\text{O}(l) \]

Write mechanism of acid dehydration of ethanol to ethene.

For a salt XY, which is a strong electrolyte, the plot of \(\Lambda_m\) versus \(\sqrt{c}\) has a slope of \(-90.0\text{ S cm}^2\text{ mol}^{-3/2}\text{ L}^{1/2}\) at \(298\text{ K}\). At \(0.01\text{ M}\) concentration of XY, the value of \(\Lambda_m\) is \(145.0\text{ S cm}^2\text{ mol}^{-1}\). The limiting molar conductivity of \(\text{Y}^-\) ion (\(\lambda^\circ_{\text{Y}^-}\), in \(\text{S cm}^2\text{ mol}^{-1}\)) at \(298\text{ K}\) will be (Given: \(\lambda^\circ_{\text{X}^+} = 74.0\text{ S cm}^2\text{ mol}^{-1}\))