At constant temperature and pressure, 5.0 l of so2 is combined with 3.0 l of o2 according to the equation:
2so2 + o2=2so3
after so3 formation is complete, what is the volume of the mixture?

Answer : The volume of mixture is, 4.99 liters.

Explanation :

First we have to calculate the moles of and .

As we know that at STP, 1 mole of substance contains 22.4 L volume of substance.

As, 22.4 L volume of present in 1 mole of

So, 5 L volume of present in mole of

And,

As, 22.4 L volume of present in 1 mole of

So, 3 L volume of present in mole of

Now we have to calculate the limiting and excess reagent.

The balanced chemical reaction is,

From the balanced reaction we conclude that

As, 2 mole of react with 1 mole of

So, 0.223 moles of react with moles of

From this we conclude that, is an excess reagent because the given moles are greater than the required moles and is a limiting reagent and it limits the formation of product.

Now we have to calculate the moles of

From the reaction, we conclude that

As, 2 mole of react to give 2 mole of

So, 0.223 moles of react to give 0.223 moles of

Now we have to calculate the volume of .

As, 1 mole of gas occupy 22.4 L volume of

So, 0.223 mole of gas occupy volume of

Therefore, the volume of the mixture is 4.99 liters.

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i believe you are right for all except the 3rd ( look at sqdancefan his answer is much better)