how many moles of ammonia are needed to react completely with 3 moles of phosphoric acid?

Answer

Explanation:

Step1: Write the chemical equation

The reaction between ammonia ($NH_3$) and phosphoric acid ($H_3PO_4$) is $3NH_3 + H_3PO_4=(NH_4)_3PO_4$.

Step2: Determine the mole - ratio

From the balanced chemical equation, the mole - ratio of $NH_3$ to $H_3PO_4$ is 3:1.

Step3: Calculate the moles of ammonia

If we have 3 moles of $H_3PO_4$, and the mole - ratio of $NH_3$ to $H_3PO_4$ is 3:1, then the moles of $NH_3$ needed is $n(NH_3)=3\times n(H_3PO_4)$. Substituting $n(H_3PO_4) = 3$ moles, we get $n(NH_3)=3\times3 = 9$ moles.

Answer:

9 moles