All the reactions are correct , so what could be the appropriate answer then?

In which reaction is dilute sulfuric acid not behaving as an acid?
a) H2SO4 + 2NaOH = Na2SO4 +2H2O
b) H2SO4 + BaCl2 = BaSO4 + 2HCl
c) H2SO4 + CuO = CuSO4 + H2O
d) H2SO4 + Mg = MgSO4 + H2
* Pardon any tying error in the equations!

2 Answers
Jun 28, 2018

Answer:

Is it not #B#?

Explanation:

The net ionic equation is simply..

#Ba^(2+) + SO_4^(2-) rarr BaSO_4(s)darr#...

The hydronium ion REMAINS in solution, i.e. #"2 equiv"# #H_3O^+#...

Just in response to a request for clarification...I will try to make what I have written less confusing... We often speak of acidity in terms of the characteristic cation of the solvent...for water we often write...

#H_2O(l)rightleftharpoonsH^+ + HO^-#...and #K_w=[HO^-][H^+]=10^-14#.

Here, #H^+# is CONCEIVED to be the acid principle...and #HO^-# is the base principle, the characteristic anion... An acid dissolved in water is INCREASES the concentration of the anion, i.e. for gaseous #HCl# we write...

#HCl(g) stackrel(H_2O)rarrH_3O^+ + Cl^-#

A saturated solution solution of #HCl(aq)# is approx #10.6*mol*L^-1# with respect to #H_3O^+#...

And of course the #H^+# is a label of convenience..in aqueous solution what we term #H^+# is possibly #H_7O_3^+# or #H_9O_4^+#...i.e. a CLUSTER of #2-3# or more water molecules WITH AN EXTRA #H^+# associated with the cluster. Certainly the #H^+# can move rapidly from cluster to cluster, tunnel if you like, given the vast aqueous mobility of #H^+# and #HO^-#...

And so we represent the acidium ion as #H^+# or even #H_3O^+#...this is a CONCEPTION rather than the reality...but it is useful to write chemical equations invoking them as actual species... I have written much the same thing here and here.

Anyway, I know that #"Inorganic Chemistry, Principles of"# #"Structure and Reactivity, J. E. Huheey"# is available in most university libraries (it may even be available for download but you might have to pledge your first-born to get it), and this has a good chapter on the concept of acidity...good luck...

Jun 29, 2018

Answer:

The correct answer is option b).

Explanation:

A substance behaves as an acid if it provides #"H"^"+"# ions that get used up during a reaction.

It is easiest to see what is happening if we use net ionic equations.

a)

Molecular equation:
#"H"_2"SO"_4"(aq)" + "2NaOH(aq)" → "Na"_2"SO"_4"(aq)" + 2"H"_2"O(l)"#

Ionic equation:
#2"H"^"+""(aq)" + color(red)(cancel(color(black)("SO"_4^"2-""(aq)"))) + color(red)(cancel(color(black)("2Na"^"+""(aq)"))) +2"OH"^"-""(aq)" → color(red)(cancel(color(black)("2Na"^"+""(aq)"))) + color(red)(cancel(color(black)("SO"_4^"2-""(aq)"))) + 2"H"_2"O(l)"#

Net ionic equation:
#color(red)(cancel(color(black)(2)))"H"^"+""(aq)" +color(red)(cancel(color(black)(2)))"OH"^"-""(aq)" → color(red)(cancel(color(black)(2)))"H"_2"O(l)"#

#"H"^"+""(aq)" +"OH"^"-""(aq)" → "H"_2"O(l)"#

#"H"^"+"# is getting used up in this reaction, so the sulfuric acid is behaving as an acid.

b)

Molecular equation:
#"H"_2"SO"_4"(aq)" + "BaCl"_2"(aq)" → "BaSO"_4"(s)" + 2"HCl""(aq)"#

Ionic equation:
#color(red)(cancel(color(black)(2"H"^"+""(aq)"))) + "SO"_4^"2-""(aq)" + "Ba"^"2+""(aq)" + color(red)(cancel(color(black)("2Cl"^"-""(aq)"))) → "BaSO"_4"(s)" + color(red)(cancel(color(black)(2"H"^"+""(aq)"))) + color(red)(cancel(color(black)("2Cl"^"-""(aq)")))#

Net ionic equation:
#"SO"_4^"2-""(aq)" + "Ba"^"2+""(aq)" → "BaSO"_4"(s)"#

#"H"^"+"# is a spectator ion.

It is not getting used up in this reaction, so the sulfuric acid is not behaving as an acid.

c)

Molecular equation:
#"H"_2"SO"_4"(aq)" + "CuO(s)" → "CuSO"_4"(aq)" + "H"_2"O(l)"#

Ionic equation:
#2"H"^"+""(aq)" + color(red)(cancel(color(black)("SO"_4^"2-""(aq)"))) + "CuO(s)" → "Cu"^"2+""(aq)" + color(red)(cancel(color(black)("SO"_4^"2-""(aq)"))) + "H"_2"O(l)"#

Net ionic equation:
#2"H"^"+""(aq)" + "CuO(s)" → "Cu"^"2+""(aq)" + "H"_2"O(l)"#

#"H"^"+"# is getting used up in this reaction, so the sulfuric acid is behaving as an acid.

d)

Molecular equation:
#"H"_2"SO"_4"(aq)" + "Mg(s)" → "MgSO"_4"(aq)" + "H"_2"(g)"#

Ionic equation:
#2"H"^"+""(aq)" + color(red)(cancel(color(black)("SO"_4^"2-""(aq)"))) + "Mg(s)" → "Mg"^"2+""(aq)" + color(red)(cancel(color(black)("SO"_4^"2-""(aq)"))) + "H"_2"(g)"#

Net ionic equation:
#2"H"^"+""(aq)" + "Mg(s)" → "Mg"^"2+""(aq)" + "H"_2"(g)"#

#"H"^"+"# is getting used up in this reaction, so the sulfuric acid is behaving as an acid.