Acetylene gas (C2H2), is used in welding torches. When it reacts with oxygen, it produces carbon dioxide (CO2), and steam (H2O). The reaction can be described by the equation 2C2H2+5O2 -> 4CO,+2H2O. How much mass of C2H2 is needed to produce 75.0 grams of CO2?

22.1 g

Explanation:

Step 1: Write the balanced equation for the combustion of acetylene

2 C₂H₂ + 5 O₂ ⇒ 4 CO₂ + 2 H₂O

Step 2: Calculate the moles corresponding to 75.0 g of CO₂

The molar mass of CO₂ is 44.01 g/mol.

75.0 g × 1 mol/44.01 g = 1.70 mol

Step 3: Calculate the moles of C₂H₂ required to produce 1.70 moles of CO₂

The molar ratio of C₂H₂ to CO₂ is 2:4. The moles of C₂H₂ required are 2/4 × 1.70 mol = 0.850 mol.

Step 4: Calculate the mass corresponding to 0.850 moles of C₂H₂

The molar mass of C₂H₂ is 26.04 g/mol.

0.850 mol × 26.04 g/mol = 22.1 g

c is the answer because when something is left after something evaporates that shows the chemical change.