f.4 chem

Which of the following substances would give the same products when either concentrated sulphuric acid or dilute suphuric acid is added?

A. Sodium hydrogencarbonate
B. Potassium bromide
C. Sugar
D. Magnesium

The answer is A.
A. For concentrated sulphuric acid,
H2SO4 (l)+ 2NaHCO3 (aq) ------＞Na2SO4 (aq) +2H2O(l) + 2CO2 (g)
For dilute suphuric acid,
H2SO4 (aq)+ 2NaHCO3 (aq) ------＞Na2SO4 (aq) +2H2O(l) + 2CO2 (g)
~SAME PRODUTS~

B. Potassium bromide has no reaction with acids~
It is chemically inert.

C. Sugar will react with concentrated sulphuric acid only.
Due to the dehydrating property of concentrated sulphuric acid .
C12H22O11 (s) ----------＞12C (s) +11H2O(g)

D. For concentrated sulphuric acid,
Mg (s) +2H2SO4 (l) ------＞MgSO4 (aq) +SO2 (g) +2H2O(l)
For dilute suphuric acid,
Mg(s) +H2SO4 (aq)--------＞MgSO4 (aq) +H2 (g)

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p.s.
D. Mg
which will not give the same products
because con. H2SO4 act as strong oxidizing agent
it oxidizes Mg
understand?*v*