List of top Chemistry Questions

The percentage of helium present in air used by scuba divers is
In a pseudo first order reaction, the following results were obtained. {|c|c|c|c|c|c|c|c|} Time s & 0 & 10 & 20 & 30 & 40 & 50 & 60
$[A]$/mol lit$^{-1}$ & 0.65 & 0.55 & 0.46 & 0.38 & 0.26 & 0.20 & 0.13
Average rate of the reaction between 20 and 40 seconds is
The molar conductivity of a weak monobasic acid, HA at 298 K is \(70\ \text{S cm}^2\text{ mol}^{-1}\). What is the percentage ionisation of HA at 298 K?
At infinite dilution \(\lambda^\circ_{H^+} = 340\ \text{S cm}^2\text{ mol}^{-1}\) and \(\lambda^\circ_{A^-} = 80\ \text{S cm}^2\text{ mol}^{-1}\)
Which of the following compound of manganese is a mixed oxide?
A first order reaction follows the equation \(k = (4 \times 10^{10}\ \text{s}^{-1}) e^{-2000/T}\). The value of \(E_a\) for the reaction is about (\(R = 8.314\ \text{J K}^{-1}\text{ mol}^{-1}\))
The solubility product, \(K_{sp}\) of a sparingly soluble salt, \(\mathrm{AX_2}\), is \(3.2 \times 10^{-14}\) mol\(^3\) lit\(^{-3}\). Its solubility is
Match the correct pH value with the following substances:
(a) Milk of magnesia (i) pH = 6.8
(b) Black coffee (ii) pH = 7.8
(c) Egg white (iii) pH = 5
(d) Milk (iv) pH = 10
The correct increasing order of enthalpy of fusion \(\Delta_{\text{fus}}H^\circ\) (in kJ mol\(^{-1}\)) of the following compounds is
Which of the following bond has highest mean bond enthalpy?
The number of bonding pairs and lone pairs of electrons in \(\mathrm{BrF_5}\) molecule are respectively
The $\Delta_r G^\circ$ of the galvanic cell in which the following cell reaction takes place, \[ 2\mathrm{Cr(s)} + 3\mathrm{Cd^{2+}(aq)} \rightarrow 2\mathrm{Cr^{3+}(aq)} + 3\mathrm{Cd(s)} \] is ($E^\circ_{\mathrm{Cr^{3+}/Cr}} = -0.74$ V and $E^\circ_{\mathrm{Cd^{2+}/Cd}} = -0.40$ V)
The empirical formula of a metal oxide which has $54\%$ metal (M) and $46\%$ oxygen (O) is (Atomic mass of M = $27$ amu and O = $16$ amu)
Which of the following elements have the highest and the lowest first ionization enthalpy?
(i) Be (ii) B (iii) C (iv) N (v) O
The radius of the first orbit of \(\mathrm{He^+}\) is
The correct increasing order of dipole moment of the following molecules is
In Mosley experiment, the X-ray spectrum is obtained by plotting
The threshold wavelength of a metal is \(6000\ \text{\AA}\). The work function of the metal is (\(h = 6.62 \times 10^{-34}\ \text{J s}\))
If the de Broglie wavelength associated with an electron is $0.1227$ nm, then its accelerating potential is
If a radiation of energy $5.2$ eV falls on the photosensitive surfaces of Mo and Ni, they emit photoelectrons with maximum kinetic energy of $0.5$ eV and $1$ eV, respectively. Then the work function of
What is the de Broglie wavelength of an electron accelerated through a potential difference of \(100\,\text{V}\)?
Which of the following is the most acidic: Ethanol, Phenol, or \(o\)-Nitrophenol?
What is the ratio of the de Broglie wavelengths of an electron and a proton moving with the same velocity?
What is the order of a reaction if the rate constant unit is \(L \cdot mol^{-1} \cdot s^{-1}\)?
Which gas is evolved when Sodium metal reacts with Ethanol?
What is the coordination number of Cobalt in $[Co(en)_3]^{3+}$?