To obtain 250 g of benzene under normal conditions, acetylene with a volume (l) is required.

Let’s write down the solution:
1. Let’s compose the reaction equation:
3C2H2 = C6H6 – the trimerization reaction occurs when heated on an incandescent
coal, benzene is released;
2. Let’s make calculations using the formulas:
M (C6H6) = 12 * 6 + 6 = 78 g / mol;
Y (C6H6) = m (C6H6) / M (C6H6) = 250/78 = 3.2 mol;
3. Let’s make a proportion according to the reaction equation:
X mol (C2H2) – 3.26 mol (C6H6);
-3 mol -1 mol hence, X mol (C2H2) = 3 * 3.2 / 1 = 9.6 mol;
4. Let’s calculate the volume of acetylene, applying Avogadro’s law:
1 mol (C2H2) – 22.4 L;
9.6 mol X L from here, Chl (C2H2) = 9.6 * 22.4 = 215 L;
Answer: the reaction requires 215 liters of acetylene.