Question

Which of the following pairs of reactants will react together to produce water (H2O) as one of the products?

NaNO3 and H2O
Mg3(PO4)2 and Al2O3
Fe(OH)3 and H2SO4
Li2O and Ba(OH)2

Answer 1

1) NaNO3 and H2O - no reaction , it is dissolution
2) no hydrogen to make water
3) Fe(OH)3 (base) and H2SO4(acid)) 
base +acid ----> salt +water
4) Li2O and Ba(OH)2
basic oxide and base ----> no reaction

so Answer number 3)
 2Fe(OH)3 +3 H2SO4 ------>   Fe2(SO4)3 + 6H2O

Answer 2

Answer: The correct pair is, $Fe(OH)_3\text{ and }H_2SO_4$

Explanation :

(1) $NaNO_3\text{ and }H_2O$

The balanced chemical reaction will be,

$NaNO_3+H_2O\rightarrow NaOH+HNO_3$

(2) $Mg_3(PO_4)_2\text{ and }Al_2O_3$

The balanced chemical reaction will be,

$Mg_3(PO_4)_2+Al_2O_3\rightarrow 2AlPO_4+3MgO$

(3) $Fe(OH)_3\text{ and }H_2SO_4$

The balanced chemical reaction will be,

$2Fe(OH)_3+3H_2SO_4\rightarrow Fe_2(SO_4)_3+6H_2O$

(4) $Li_2O\text{ and }Ba(OH)_2$

The balanced chemical reaction will be,

$Li_2O+Ba(OH)_2\rightarrow 2LiOH+BaO$

Hence, the pairs of reactants react together to produce water as one of the product will be, $Fe(OH)_3\text{ and }H_2SO_4$