Question

gas stoichiometry at stp
2c₂h₂(g) + 5o₂(g) → 4co₂(g) + 2h₂o(g)
you want to calculate the number of liters of c₂h₂ that react with 12.0 mol o₂, assuming the reaction is at stp.
use the dimensional analysis below to set up the two - step calculation.
12.0 mol o₂
which ratio should be used for the first conversion, from moles o₂ to moles c₂h₂?
ratio 1
ratio 4
ratio 2
ratio 3

Explanation:

The balanced chemical equation is \(2\text{C}_2\text{H}_2(g) + 5\text{O}_2(g)
ightarrow 4\text{CO}_2(g) + 2\text{H}_2\text{O}(g)\). The mole ratio of \(\text{C}_2\text{H}_2\) to \(\text{O}_2\) from the equation is 2:5. To convert moles of \(\text{O}_2\) to moles of \(\text{C}_2\text{H}_2\), we use the ratio of moles of \(\text{C}_2\text{H}_2\) to moles of \(\text{O}_2\), which is 2/5. Among the given options, ratio 2 corresponds to the numerator of this mole ratio (moles of \(\text{C}_2\text{H}_2\)).

Answer:

ratio 2