# A volume of 20*cm^3 acetylene was combusted with a volume of 500*cm^3 dioxygen in a piston. What is the end volume of the gases confined by the piston?

Aug 29, 2017

Good question......I gets an end volume of $490 \cdot c {m}^{3}$

#### Explanation:

We gots the combustion equation.....

$H C \equiv C H \left(g\right) + \frac{5}{2} {O}_{2} \left(g\right) \rightarrow 2 C {O}_{2} \left(g\right) + {H}_{2} O \left(l\right) + \Delta$

I use the half-integral coefficient because I think the arithmetic is easier in this way. Is it balanced? It is your problem not mine.

And so we start with $20 \cdot c {m}^{3}$ acetylene, which required $50 \cdot c {m}^{3}$ of dioxygen, and gives $40 \cdot c {m}^{3}$ carbon dioxide gas upon complete combustion. I assume that the water has condensed. Agreed?

And so to begin we had a $\left({20}_{\text{acetylene"+500_"dioxygen}}\right) \cdot c {m}^{3}$ volume of gas.....

To end we had ............ $\left({520}_{\text{starting volume"-50_"dioxygen"-20_"acetylene}} + {40}_{C {O}_{2}}\right) \cdot c {m}^{3} = 490 \cdot c {m}^{3}$

Do you agree? All care taken but no responsibility admitted.