To find the ratio of [tex]\( NH_3 \)[/tex] to [tex]\( H_3PO_4 \)[/tex] in the given reaction, we start by examining the balanced chemical equation:
[tex]\[
2 NH_3 + H_3PO_4 \rightarrow (NH_4)_2HPO_4
\][/tex]
The coefficients in the balanced chemical equation indicate the molar ratios of the reactants and products. Here, the coefficient of [tex]\( NH_3 \)[/tex] is 2 and the coefficient of [tex]\( H_3PO_4 \)[/tex] is 1.
This means that for every 2 moles of [tex]\( NH_3 \)[/tex] used, 1 mole of [tex]\( H_3PO_4 \)[/tex] is required.
Thus, the ratio of [tex]\( NH_3 \)[/tex] to [tex]\( H_3PO_4 \)[/tex] is:
[tex]\[
NH_3 : H_3PO_4 = 2 : 1
\][/tex]
Therefore, the missing number in the ratio [tex]\( NH_3 : H_3PO_4 = 2 : \square \)[/tex] is:
[tex]\[
NH_3 : H_3PO_4 = 2 : 1
\][/tex]
