Answer : The correct option is, (B) Salicylic acid
Solution :
First we have to calculate the moles of salicylic acid and acetic anhydride.
[tex]\text{Moles of }C_7H_6O_3=\frac{\text{Mass of }C_7H_6O_3}{\text{Molar mass of }C_7H_6O_3}=\frac{70g}{138.121g/mole}=0.507moles[/tex]
[tex]\text{Moles of }C_4H_6O_3=\frac{\text{Mass of }C_4H_6O_3}{\text{Molar mass of }C_4H_6O_3}=\frac{80g}{102.09g/mole}=0.783moles[/tex]
Now we have to calculate the limiting and excess reagent.
The balanced chemical reaction is,
[tex]2C_7H_6O_3(aq)+C_4H_6O_3(aq)\rightarrow 2C_9H_8O_4(aq)+H_2O(l)[/tex]
From the balanced reaction we conclude that
As, 2 moles of salicylic acid react with 1 mole of acetic anhydride
So, 0.507 moles of salicylic acid react with [tex]\frac{0.507}{2}=0.2535[/tex] mole of acetic anhydride
The excess of acetic anhydride = 0.783 - 0.2535 = 0.5295 moles
That means the in the given balanced reaction, salicylic acid is a limiting reagent because it limits the formation of products and acetic anhydride is an excess reagent.
Hence, the limiting reagent is, salicylic acid.
