Question

Question #90325

Answer 1

Incorrect.

Explanation:

You don't even need a balanced chemical equation to answer this question, all you need to know is that when cellulose undergoes complete combustion, the reaction produces carbon dioxide--keep in mind that this is an oversimplification of what happens when you burn cellulose!

`"cellulose"_ ((s)) + "enough O"_ (2(g)) -> "solid residue"_ ((s)) +"CO"_ (2(g)) + "H"_ 2"O"_ ((l))`

Now, if you dissolve carbon dioxide in water, you will get an acidic solution, not an alkaline solution.

This happens because some of the dissolved carbon dioxide molecules will react with water to form carbonic acid, `"H"_2"CO"_3`, which, as its name suggests, acts as an acid in aqueous solution.

So you can say that you have

`"CO"_ (2(g)) rightleftharpoons "CO"_ (2(aq))`

followed by

`"CO" _ (2(aq)) + "H"_ 2"O"_ ((l)) rightleftharpoons "H"_ 2"CO"_ (3(aq))`

and

`"H"_ 2"CO"_ (3(aq)) rightleftharpoons "H"_ ((aq))^(+) + "HCO"_ (3(aq))^(-)`

You can thus say that when carbon dioxide is dissolved in water, the resulting solution is acidic, i.e. it has a `"pH"` that is `<7` at room temperature, because aqueous carbon dioxide increases the concentration of hydrogen ions, `"H"^(+)`, present in the solution.

`"CO" _ (2(aq)) + "H"_ 2"O"_ ((l)) rightleftharpoons "H"_ 2"CO"_ (3(aq)) rightleftharpoons "H"_ ((aq))^(+) + "HCO"_ (3(aq))^(-)`

By comparison, ammonia, `"NH"_3`, behaves as an alkaline in aqueous solution because it increases the concentration of hydroxide anions, `"OH"^(-)`, present in the solution.

In this case, you have

`"NH"_ (3(g)) rightleftharpoons "NH"_ (3(aq))`

followed by

`"NH"_ (3(aq)) + "H"_ 2"O"_ ((l)) rightleftharpoons "NH"_ (4(aq))^(+) + "OH"_ ((aq))^(-)`