To determine the mass of magnesium (Mg) required to produce 220 mL of hydrogen gas (H2) at Standard Temperature and Pressure (STP) when reacted with excess dilute hydrochloric acid (HCl), we start by considering the balanced chemical reaction:
\(\text{Mg} + 2\text{HCl} \rightarrow \text{MgCl}_{2} + \text{H}_2 \uparrow\)
\(\text{Moles of H}_2 = \frac{220 \, \text{mL}}{22400 \, \text{mL/mol}} = 0.00982 \, \text{mol}\)
\(\text{Mass of Mg} = 0.00982 \, \text{mol} \times 24 \, \text{g/mol} = 0.23568 \, \text{g}\)
\(0.23568 \, \text{g} = 235.68 \, \text{mg} \approx 236 \, \text{mg}\)
Thus, the mass of magnesium required is approximately 236 mg.
Conclusion: The correct answer is 236 mg.
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)

Cobalt chloride when dissolved in water forms pink colored complex $X$ which has octahedral geometry. This solution on treating with cone $HCl$ forms deep blue complex, $\underline{Y}$ which has a $\underline{Z}$ geometry $X, Y$ and $Z$, respectively, are
What will be the equilibrium constant of the given reaction carried out in a \(5 \,L\) vessel and having equilibrium amounts of \(A_2\) and \(A\) as \(0.5\) mole and \(2 \times 10^{-6}\) mole respectively?
The reaction : \(A_2 \rightleftharpoons 2A\)