1. Determine the moles of H₂

* The molar mass of H₂ is 2.016 g/mol.

* Divide the given mass of H₂ by its molar mass:

200 g H₂ / 2.016 g/mol = 99.2 mol H₂

2. Use the stoichiometry of the reaction

* The balanced chemical equation for the reaction is:

C₂H₂ → 2H₂

* This equation tells us that 1 mole of C₂H₂ produces 2 moles of H₂.

3. Calculate the moles of C₂H₂ needed

* Since the ratio is 1:2, we need half the moles of C₂H₂ compared to H₂.

* Moles of C₂H₂ = 99.2 mol H₂ / 2 = 49.6 mol C₂H₂

4. Apply the Ideal Gas Law to find the volume

* The Ideal Gas Law is: PV = nRT

* P = Pressure (standard pressure is 1 atm)

* V = Volume (what we want to find)

* n = Number of moles (49.6 mol C₂H₂)

* R = Ideal gas constant (0.0821 L·atm/mol·K)

* T = Temperature (standard temperature is 273.15 K)

* Solve for V:

V = (nRT) / P

V = (49.6 mol * 0.0821 L·atm/mol·K * 273.15 K) / 1 atm

V = 1110 L

Therefore, approximately 1110 liters of C₂H₂ would be required at standard pressure to obtain 200 grams of H₂.