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[holaa]

5 dm³ of carbon monoxide, CO(g), and 2 dm³ of oxygen, O₂(g), at the same temperature and pressure are mixed together. Assuming complete reaction according to the equation given, what is the maximum volume of carbon dioxide, CO₂(g), in dm³, that can be formed?

 

2CO(g) + O₂(g) → 2CO₂(g)

 

The answer is 4, but I don't know how to get there, can someone please explain this. Am I supposed to change the dm3 to moles?

[IB_taking_over]

You don't need to convert to moles. It is basically like fairly simple algebra equation. (There may be a faster way to do this; It's been a few years since I've done anything chemistry related.)

We know that 2CO(g) + O₂(g) → 2CO₂(g) which means it takes 2 CO and 1 O2 to make 2 CO2. We have 5 dm³ of CO(g), and 2 dm³ of O₂(g) And we want to know much CO₂(g), in dm³ these will produce.

Since the units are all the same we don't need to convert anything.

So, 

Step 1 - find the limiting reagent. The O2 can make 2 CO2 and the CO2 can make 2.5 CO2. So O2 is the limiting reagent.

Step 2 - multiply the reaction equation by the amount the limiting reagent can produce. 2(2CO(g) + 1O₂(g) → 2CO₂(g))

We get: 4CO(g) + 2O₂(g) → 4CO₂(g)

So, 4 dm3 CO2

Hopefully this make sense. If not hopefully someone else can explain it better 🙂