Question

If the acetylene tank contains 37.0 moles of c2h2 an oxygen tank contains 81.0 moles of o2 what is the limiting reactant for this reaction

Answer 1

2C2H2 + 5O2 ---> 4CO2 + 2H2O 
mole ratio of O2:C2H2 is 2.5:1 
for 37 mol C2H2 you need 2.5 x 37 mol = 92.5 moles O2. 
Thus, O2 is limiting.

Answer 2

Answer:

Oxygen is the limiting reactant for this reaction

Explanation:

$2C_2H_2+5O_2\rightarrow 4CO_2+2H_2O$

According to reaction, 2 moles of acetylene reacts with 5 moles of oxygen.

If there 37.0 moles of acetylene, then they will react with:

$\frac{5}{2}\times 37.0=92.5 mol$

If there 81.0 moles of oxygen, then they will react with:

$\frac{2}{5}\times 81.0=32.4 mol$

As we can see that 81 moles of oxygen will completely react with 32.4 moles of acetylene.

But we are given with 37 moles of acetylene which means that oxygen is present in limiting amount and acetylene is present ion excessive amount.