Question

If 200 ml of 0.3 M $H_{3}P{O}_3$ is mixed with 200 ml of 0.3 M $Ba(OH{)}_2$, find the incorrect option from the following:

• A. $H_{3}P{O}_3$ is limiting reagent if the reaction goes to completion
• B. $H_{3}P{O}_3$ is the limiting reagent if $Ba(H_{2}P{O}_3{)}_2$ is the product
• C. Reactants get used up if $Ba\left(OH\right)\left(H_{2}P{O}_3\right)$ is the product.
• D. Reactants get used up if $Ba\left(HP{O}_3\right)$ is the product

Answer 1

The correct option is A $H_{3}P{O}_3$ is limiting reagent if the reaction goes to completion

Limiting reagent is the subtance that is fully consumed in the reaction.
We have 60 mmol of each compound.
a) If the complete reaction takes place then the balanced equation will be
$3Ba(OH{)}_2+2H_{3}P{O}_3\to B{a}_3(P{O}_3{)}_2+6H_{2}O$
So we need 90 mmol $Ba(OH{)}_2$ to react with 60 mmol $H_{3}P{O}_3$. Hence $Ba(OH{)}_2$ is the limiting reagent here.
b) The balanced chemical equation in this case will be$Ba(OH{)}_2+2H_{3}P{O}_3\to Ba(H_{2}P{O}_3{)}_2+2H_{2}O$
Here we need 120 mmol $H_{3}P{O}_3$ to react with 60 mmol $Ba(OH{)}_2$.Hence $H_{3}P{O}_3$ is the limiting reagent here.
c) The balanced chemical equation in this case will be
$Ba(OH{)}_2+H_{3}P{O}_3\to Ba\left(OH\right)\left(H_{2}P{O}_3\right)+H_{2}O$
There is no limiting reagent in this case.
d) Here the balanced chemical equation will be $Ba(OH{)}_2+H_{3}P{O}_3\to Ba(HP{O}_3)+2H_{2}O$
So similar to (c), no limiting reagent is there in the reaction.