Sulfur dioxide gas, SO2 (g), is released from active volcanoes. It reacts in the atmosphere to form sulfur trioxide, SO3 (g).

2SO2 (g) + O2 (g) → 2SO3 (g)

Which statement (s) best describes the reaction? Check all that apply.

- The reaction is balanced.

- When 2 L SO2 react with excess O2, 2 mol SO3 form

- The coefficients can represent moles, molecules, or liters.

1st and 3rd options

Explanation:

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The reaction given:

2SO2 (g) + O2 (g) - > 2SO3 (g)

A. "The reaction is balanced."

We multiply the sulphur atoms on both sides:

2S - > 2S, ... 2 sulphur atoms on each side, so balanced.

now oxygen:

2O2+O2 - > 2O3 ... 6 atoms on each side, so also balanced.

This means that the equation is balanced.

B. "When 2 L SO2 react with excess O2, 2 mol SO3 form "

The coefficient of reactant SO2 is 2, so is that of the product. If we had the same units on either side of the equation (mols, litres, molecules), the statement would have been true. Since 2L of SO2 does not contain 2 mol of SO2, so the statement is no longer true.

C. "The coefficients can represent moles, molecules, or liters"

As mentioned in (B) above, we can use moles, molecules or litres (or any other volume unit) to apply to the coefficient and the equation will still be true. So the statement is true.