Does the type of acid affect the mass of product formed?
2018-05-23 8:20 pm
Say, for example, calcium carbonate reacts with hydrochloric acid to produce carbon dioxide gas. Would the same reaction with sulphuric acid produce a different mass of carbon dioxide?
回答 (2)
2018-05-23 10:11 pm
Suppose that calcium carbonate is the limiting reactant/reagent and an excess of acid is used. Much less carbon dioxide is formed when sulphuric acid is used instead of hydrochloric acid.
The equations of the two reactions are :
CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g)
CaCO₃(s) + 2H₂SO₄(aq) → CaSO₄(s) + H₂O(l) + CO₂(g)
When hydrochloric acid is used (the first equation), the reaction goes completion. Calcium carbonate reacts completely to form carbon dioxide gas.
When sulphuric acid is used (the second equation), the calcium sulphate formed is solid. The calcium sulphate would form a solid layer to cover the calcium carbonate solid. Then, the two reactants (calcium carbonate and sulphuric acid) are separated by the layer of the calcium carbonate formed. Therefore, the reaction stops soon after the reaction starts. As the reaction does not complete, a smaller amount of carbon dioxide gas is formed when sulphuric acid is used instead of hydrochloric acid.
The equations of the two reactions are :
CaCO₃(s) + 2HCl(aq) → CaCl₂(aq) + H₂O(l) + CO₂(g)
CaCO₃(s) + 2H₂SO₄(aq) → CaSO₄(s) + H₂O(l) + CO₂(g)
When hydrochloric acid is used (the first equation), the reaction goes completion. Calcium carbonate reacts completely to form carbon dioxide gas.
When sulphuric acid is used (the second equation), the calcium sulphate formed is solid. The calcium sulphate would form a solid layer to cover the calcium carbonate solid. Then, the two reactants (calcium carbonate and sulphuric acid) are separated by the layer of the calcium carbonate formed. Therefore, the reaction stops soon after the reaction starts. As the reaction does not complete, a smaller amount of carbon dioxide gas is formed when sulphuric acid is used instead of hydrochloric acid.
2018-05-23 10:30 pm
Does the type of acid affect the mass of CO2?
No. It won't make any difference whether the acid is HCl, HNO3, H2SO4 or H3PO4. The amount of CO2 produced will be ENTIRELY dependent on the amount of the carbonate salt.
Your question says "type of acid", not amount of acid. Whether the acid is monoprotic or polyprotic won't have an effect on the CO2 volume. The amount of CO2 will depend only the amount of CaCO3.
====== Follow up ======
Ok, let's back the boat up. I think we can all agree on the fact that this is not the most well-worded question. It only makes sense to compare the "type" of acid when the calcium carbonate is the limiting reactant. A somewhat better question would be, "Does the type of acid make any difference if 100.0g of calcium carbonate completely reacts?" This establishes that CaCO3 is the limiting reactant. In such a case only the CaCO3 will determine the amount of CO2 produced and the type of acid (or the volume or the concentration) will not matter because the CO2 comes from 100.0g of CaCO3.
If the acid is the limiting reactant, then the "type" of acid is not the only factor, and the question must refer to the volume and concentration of the acids, if only to say that they are the same. But the question doesn't mention that information, which is why we can infer than that CaCO3 is the limiting reactant.
And if CaCO3 is the limiting reactant, and the acid is assumed to be in excess, then the type of acid, won't matter.
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"Question mark" (What's with the proliferation of question marks for names?) brings up another point: the reaction of the calcium ion and the anion of the acid. Suppose H2SO4 and H3PO4 are used, then we can expect some precipitation of CaSO4, Ca(H2PO4)2, CaHPO4, and Ca3(PO4)2 all of which are progressively less soluble in water. The trick is to keep the precipitate off of the CaCO3 with agitation, stirring or other mechanical means, in order to allow all of the CaCO3 to react.
No. It won't make any difference whether the acid is HCl, HNO3, H2SO4 or H3PO4. The amount of CO2 produced will be ENTIRELY dependent on the amount of the carbonate salt.
Your question says "type of acid", not amount of acid. Whether the acid is monoprotic or polyprotic won't have an effect on the CO2 volume. The amount of CO2 will depend only the amount of CaCO3.
====== Follow up ======
Ok, let's back the boat up. I think we can all agree on the fact that this is not the most well-worded question. It only makes sense to compare the "type" of acid when the calcium carbonate is the limiting reactant. A somewhat better question would be, "Does the type of acid make any difference if 100.0g of calcium carbonate completely reacts?" This establishes that CaCO3 is the limiting reactant. In such a case only the CaCO3 will determine the amount of CO2 produced and the type of acid (or the volume or the concentration) will not matter because the CO2 comes from 100.0g of CaCO3.
If the acid is the limiting reactant, then the "type" of acid is not the only factor, and the question must refer to the volume and concentration of the acids, if only to say that they are the same. But the question doesn't mention that information, which is why we can infer than that CaCO3 is the limiting reactant.
And if CaCO3 is the limiting reactant, and the acid is assumed to be in excess, then the type of acid, won't matter.
============
"Question mark" (What's with the proliferation of question marks for names?) brings up another point: the reaction of the calcium ion and the anion of the acid. Suppose H2SO4 and H3PO4 are used, then we can expect some precipitation of CaSO4, Ca(H2PO4)2, CaHPO4, and Ca3(PO4)2 all of which are progressively less soluble in water. The trick is to keep the precipitate off of the CaCO3 with agitation, stirring or other mechanical means, in order to allow all of the CaCO3 to react.
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