Question

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

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