List of top Chemistry Questions asked in GATE ES

The molar concentrations (M, i.e. mol/L) of some ionic species in a water sample were estimated as follows: \[ \text{Na}^+ = 0.25 \, \text{M}; \, \text{Ca}^{2+} = 0.12 \, \text{M}; \, \text{Cl}^- = 0.32 \, \text{M}; \, \text{HCO}_3^- = 0.05 \, \text{M}. \] The ionic strength of this water sample is _______ M (correct up to two decimal places).
Excess amount of solid calcium sulphate (CaSO\(_4\)) was added to a pure water sample (pH = 7) so that some solids remain undissolved at the equilibrium. The solubility product of CaSO\(_4\) is \( 2 \times 10^{-5} \, \text{mol}^2/\text{L}^2 \). The molar concentration of SO\(_4^{2-}\) in this water sample at equilibrium will be _______ mol/L (rounded off to three decimal places).
A 200 mL sample of water has an initial pH = 9. In order to determine alkalinity, the sample was titrated using 0.02 N \( \text{H}_2\text{SO}_4 \) acid to an end point of pH = 4.5. In the titration, 25 mL of 0.02 N \( \text{H}_2\text{SO}_4 \) acid was required. What is the total alkalinity of the sample in ‘mg/L as NaHCO\(_3\)’? [Atomic weight (g/mol): Ca = 40, Na = 23, H = 1, C = 12, S = 32, and O = 16]
What is the pH of a water sample having \( H^+ \) concentration of 10 mg/L? The atomic weight of H is 1 g/mol.
The oxidation states of ‘N’ in \( \text{NH}_4^+ \), \( \text{NO}_2^- \), and \( \text{NO} \) are _______ , respectively.