List of top Environmental Chemistry Questions

The calibration graph between absorbance and the concentration of chromate (\(CrO_4^{2-}\)) in a water sample is shown in the figure.

The calibration line shown in the figure has the equation \(y = 0.8003x + 0.0055\), where \(y\) is the absorbance and \(x\) is the concentration of chromate (\(CrO_4^{2-}\), mg/L).

For an absorbance of 0.35 in a water sample, the estimated Cr(VI) concentration is ______ mg/L (rounded off to two decimal places).

Use the atomic weight (g/mol) of Cr and O as 52 and 16, respectively.

The following two reactions describe the chemistry of S(IV) in an aquatic system.

Under ideal conditions, the equilibrium constants for reactions (i) and (ii) are \(1.3\times10^{-2}\ M\) (\(K_{S1}\)) and \(6.6\times10^{-8}\ M\) (\(K_{S2}\)), respectively.

If the pH of the system is 4.0 and the equilibrium concentration of \(SO_{2(aq)}\) is 1.0 M, the equilibrium concentration of \(SO_3^{2-}\) is ______ mM (rounded off to one decimal place).

\[SO_{2(aq)} \rightleftharpoons H^+ + HSO_3^- \quad (i)\]

\[HSO_3^- \rightleftharpoons H^+ + SO_3^{2-} \quad (ii)\]