List of top Chemistry Questions

In a reaction 2A $\rightarrow$ product, the concentration of A decreases from 0.5 M to 0.4 M in 10 minutes. The rate of the reaction (in mol $L^{-1} min^{-1}$) is:

At T(K), 0.004 M $Na_2SO_4$ solution is isotonic with 0.01 M glucose solution. The degree of dissociation of $Na_2SO_4$ is:

Which of the following point defects are shown by AgBr crystals? I. Metal excess defect, II. Schottky defect, III. Metal deficiency defect, IV. Frenkel defect

At 298 K, $E^{\circ}$ value of the cell involving $2 Fe^{3+}(aq) + 2 I^-(aq) \rightarrow 2 Fe^{2+}(aq) + I_2(s)$ is X V. The X (in V) and $\log K_c$ for the reaction are respectively: ($E^{\circ}_{Fe^{3+}/Fe^{2+}} = 0.77$ V, $E^{\circ}_{I_2/I^-} = 0.54$ V)

Consider the following carbocations: (I) $(CH_3)_2CH-CH_2^+$, (II) $CH_2=CH-C^+H-CH_3$, (III) $(CH_3)_2CH-C^+H-CH_3$. The correct order of stabilities of these is:

0.42 g of an organic compound containing C, H and O gave on combustion 0.942 g of $CO_2$ and 0.231 g of $H_2O$. The empirical formula weight of the compound is (At.wt: $C=12$ u, $H=1$ u, $O=16$ u)

In which of the following, pollutant in air/water is not correctly matched with its effect?

Which of the following are the properties of silicones? I. Water repelling in nature II. High thermal stability III. Easily oxidisable IV. High dielectric strength

The covalent hydrides of elements X and Y act as Lewis acid and Lewis base respectively. Covalent hydride of element Z is neither Lewis acid nor Lewis base. What are X, Y and Z respectively?

Identify the correct order of the given compounds against the given property:

Borax $+ H_2O \rightarrow A + B$. What are A and B respectively?

White phosphorus reacts with aqueous NaOH solution to form $PH_3(g)$ and aqueous sodium salt of hypophosphorus acid. 12.4 g of white phosphorus was dissolved in 500 mL of xM NaOH solution. The concentration of sodium salt of hypophosphorus acid in the resultant solution was 0.6 mol $L^{-1}$. What is the value of x in mol $L^{-1}$? (P=31u)

A solution is prepared by adding 0.5 L of 0.5 M NaOH solution to 0.5 L of x M HCOOH solution. The pH of resultant solution is 4.74. What is x in mol $L^{-1}$? (pKa (HCOOH) = 3.74)

What is the bond enthalpy (in kJ $mol^{-1}$) of C-H in ethane? ($\Delta_f H^{\ominus}(C_2H_6(g)) = -85$ kJ $mol^{-1}$; $H_2(g) \rightarrow 2H(g); \Delta_a H^{\ominus} = 435$ kJ $mol^{-1}$; $C(s) \rightarrow C(g); \Delta_a H^{\ominus} = 715$ kJ $mol^{-1}$; $\Delta_a H^{\ominus}(C-C) = 347$ kJ $mol^{-1}$)

What is the work done (in J $mol^{-1}$) to vaporise 1 mole of $H_2O(l)$ to $H_2O(g)$ at 1 bar pressure and $100^{\circ}C$? ($\Delta_{vap}H = 41$ kJ $mol^{-1}$; $\Delta U = 37.9$ kJ $mol^{-1}$)

For a fixed amount of an ideal gas, its pressure is measured as a function of volume at three different temperatures ($T_1, T_2, T_3$). What is the correct order of temperatures? figure [H]

figure

One mole of $A(g)$ was taken in a 1L closed flask and heated to T(K). At equilibrium, the concentration of $A(g)$ is equal to four times the equilibrium concentration of $B(g)$. What is $K_c$ for $A(g) \rightleftharpoons B(g) + C(g)$?

A photon of energy 12.09 eV is absorbed by a hydrogen atom in its first excited state, resulting in the ejection of an electron. The kinetic energy (in J) of the emitted photoelectron is ($1 eV = 1.6 \times 10^{-19}$ J, $R_H = 13.6$ eV):

Which of the following is the correct increasing order of atomic number of elements A, B and C of third period, if their oxides are amphoteric, basic and acidic in nature respectively?

Which of the following set of quantum numbers represent the electron with highest energy?

The geometry and hybridisation of central atom of the volatile product formed when calamine is heated are respectively:

Match the following: figure [H]

figure

The reaction $A(g) \rightleftharpoons B(g) + C(g)$ was initiated with the amount 'a' of $A(g)$. At equilibrium it is found that the amount of $A(g)$ remaining is $(a - x)$ at a total pressure of p.
The equilibrium constant $K_p$ of the reaction can be calculated from the expression :

First order gas phase reaction \(A \to B + C\). \(p_i = \text{initial pressure of gas A}\), \(P_t = \text{total pressure of the reaction mixture at time t}\). Expression of rate constant (k) is

For a reaction $A \to P$ at $T$ K, the half life ($t_{1/2}$) is plotted as a function of initial concentration $[A]_o$ of A as given below. The value of $x$ in the given figure is ______ s (Nearest integer)}